mysql parser refactor

src/main/java/com/alibaba/druid/sql/ast/statement/SQLAlterTableDropColumnItem.java

@@ -0,0 +1,28 @@
+package com.alibaba.druid.sql.ast.statement;
+
+import com.alibaba.druid.sql.ast.SQLName;
+import com.alibaba.druid.sql.ast.SQLObjectImpl;
+import com.alibaba.druid.sql.visitor.SQLASTVisitor;
+
+public class SQLAlterTableDropColumnItem extends SQLObjectImpl implements SQLAlterTableItem {
+
+    private static final long serialVersionUID = 1L;
+    private SQLName           columnName;
+
+    @Override
+    protected void accept0(SQLASTVisitor visitor) {
+        if (visitor.visit(this)) {
+            acceptChild(visitor, columnName);
+        }
+        visitor.endVisit(this);
+    }
+
+    public SQLName getColumnName() {
+        return columnName;
+    }
+
+    public void setColumnName(SQLName columnName) {
+        this.columnName = columnName;
+    }
+
+}

src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/statement/MySqlAlterTableAddColumn.java

@@ -0,0 +1,38 @@
+package com.alibaba.druid.sql.dialect.mysql.ast.statement;
+
+import com.alibaba.druid.sql.ast.SQLName;
+import com.alibaba.druid.sql.ast.statement.SQLAlterTableAddColumn;
+import com.alibaba.druid.sql.dialect.mysql.ast.MySqlObject;
+import com.alibaba.druid.sql.dialect.mysql.visitor.MySqlASTVisitor;
+import com.alibaba.druid.sql.visitor.SQLASTVisitor;
+
+public class MySqlAlterTableAddColumn extends SQLAlterTableAddColumn implements MySqlObject {
+
+    private static final long serialVersionUID = 1L;
+
+    private SQLName           after;
+
+    public SQLName getAfter() {
+        return after;
+    }
+
+    public void setAfter(SQLName after) {
+        this.after = after;
+    }
+
+    @Override
+    protected void accept0(SQLASTVisitor visitor) {
+        if (visitor instanceof MySqlASTVisitor) {
+            accept0((MySqlASTVisitor) visitor);
+        } else {
+            throw new IllegalArgumentException("not support visitor type : " + visitor.getClass().getName());
+        }
+    }
+
+    public void accept0(MySqlASTVisitor visitor) {
+        if (visitor.visit(this)) {
+            acceptChild(visitor, getColumns());
+        }
+        visitor.endVisit(this);
+    }
+}

src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/statement/MySqlAlterTableStatement.java

@@ -4,11 +4,12 @@ import com.alibaba.druid.sql.ast.statement.SQLAlterTableStatement;
 import com.alibaba.druid.sql.dialect.mysql.visitor.MySqlASTVisitor;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
-
 public class MySqlAlterTableStatement extends SQLAlterTableStatement {
 
     private static final long serialVersionUID = 1L;
 
+    private boolean           ignore           = false;
+
     @Override
     protected void accept0(SQLASTVisitor visitor) {
         if (visitor instanceof MySqlASTVisitor) {
@@ -17,8 +18,21 @@ public class MySqlAlterTableStatement extends SQLAlterTableStatement {
             throw new IllegalArgumentException("not support visitor type : " + visitor.getClass().getName());
         }
     }
-    
+
     public void accept0(MySqlASTVisitor visitor) {
-        throw new UnsupportedOperationException(this.getClass().getName());
+        if (visitor.visit(this)) {
+            acceptChild(visitor, getTableSource());
+            acceptChild(visitor, getItems());
+        }
+        visitor.endVisit(this);
     }
+
+    public boolean isIgnore() {
+        return ignore;
+    }
+
+    public void setIgnore(boolean ignore) {
+        this.ignore = ignore;
+    }
+
 }

src/main/java/com/alibaba/druid/sql/dialect/mysql/parser/MySqlStatementParser.java

@@ -26,6 +26,8 @@ import com.alibaba.druid.sql.ast.expr.SQLIdentifierExpr;
 import com.alibaba.druid.sql.ast.expr.SQLLiteralExpr;
 import com.alibaba.druid.sql.ast.expr.SQLQueryExpr;
 import com.alibaba.druid.sql.ast.expr.SQLVariantRefExpr;
+import com.alibaba.druid.sql.ast.statement.SQLAlterTableDropColumnItem;
+import com.alibaba.druid.sql.ast.statement.SQLColumnDefinition;
 import com.alibaba.druid.sql.ast.statement.SQLCreateTableStatement;
 import com.alibaba.druid.sql.ast.statement.SQLDropTableStatement;
 import com.alibaba.druid.sql.ast.statement.SQLInsertStatement;
@@ -35,6 +37,8 @@ import com.alibaba.druid.sql.ast.statement.SQLTableSource;
 import com.alibaba.druid.sql.ast.statement.SQLUpdateSetItem;
 import com.alibaba.druid.sql.ast.statement.SQLUpdateStatement;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.CobarShowStatus;
+import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlAlterTableAddColumn;
+import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlAlterTableStatement;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlBinlogStatement;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlCommitStatement;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlCreateUserStatement;
@@ -506,12 +510,12 @@ public class MySqlStatementParser extends SQLStatementParser {
 
             return stmt;
         }
-        
+
         if (identifierEquals("VARIABLES")) {
             lexer.nextToken();
-            
+
             MySqlShowVariantsStatement stmt = parseShowVariants();
-            
+
             return stmt;
         }
 
@@ -524,7 +528,7 @@ public class MySqlStatementParser extends SQLStatementParser {
                 stmt.setGlobal(true);
                 return stmt;
             }
-            
+
             if (identifierEquals("VARIABLES")) {
                 lexer.nextToken();
                 MySqlShowVariantsStatement stmt = parseShowVariants();
@@ -542,7 +546,7 @@ public class MySqlStatementParser extends SQLStatementParser {
                 stmt.setSession(true);
                 return stmt;
             }
-            
+
             if (identifierEquals("VARIABLES")) {
                 lexer.nextToken();
                 MySqlShowVariantsStatement stmt = parseShowVariants();
@@ -970,24 +974,24 @@ public class MySqlStatementParser extends SQLStatementParser {
 
             return stmt;
         }
-        
+
         if (identifierEquals("RELAYLOG")) {
             lexer.nextToken();
             acceptIdentifier("EVENTS");
             MySqlShowRelayLogEventsStatement stmt = new MySqlShowRelayLogEventsStatement();
-            
+
             if (lexer.token() == Token.IN) {
                 lexer.nextToken();
                 stmt.setLogName(this.exprParser.primary());
             }
-            
+
             if (lexer.token() == Token.FROM) {
                 lexer.nextToken();
                 stmt.setFrom(this.exprParser.primary());
             }
-            
+
             stmt.setLimit(this.parseLimit());
-            
+
             return stmt;
         }
 
@@ -1022,7 +1026,7 @@ public class MySqlStatementParser extends SQLStatementParser {
                 return stmt;
             }
         }
-        
+
         if (lexer.token() == Token.TABLE) {
             lexer.nextToken();
             acceptIdentifier("STATUS");
@@ -1031,7 +1035,7 @@ public class MySqlStatementParser extends SQLStatementParser {
                 lexer.nextToken();
                 stmt.setDatabase(this.exprParser.name());
             }
-            
+
             if (lexer.token() == Token.LIKE) {
                 lexer.nextToken();
                 stmt.setLike(this.exprParser.expr());
@@ -1041,10 +1045,10 @@ public class MySqlStatementParser extends SQLStatementParser {
                 lexer.nextToken();
                 stmt.setWhere(this.exprParser.expr());
             }
-            
+
             return stmt;
         }
-        
+
         if (identifierEquals("TRIGGERS")) {
             lexer.nextToken();
             MySqlShowTriggersStatement stmt = new MySqlShowTriggersStatement();
@@ -1091,22 +1095,22 @@ public class MySqlStatementParser extends SQLStatementParser {
 
         return stmt;
     }
-    
+
     private MySqlShowVariantsStatement parseShowVariants() throws ParserException {
         MySqlShowVariantsStatement stmt = new MySqlShowVariantsStatement();
-        
+
         if (lexer.token() == Token.LIKE) {
             lexer.nextToken();
             SQLExpr like = exprParser.expr();
             stmt.setLike(like);
         }
-        
+
         if (lexer.token() == Token.WHERE) {
             lexer.nextToken();
             SQLExpr where = exprParser.expr();
             stmt.setWhere(where);
         }
-        
+
         return stmt;
     }
 
@@ -1785,9 +1789,101 @@ public class MySqlStatementParser extends SQLStatementParser {
 
         return null;
     }
-    
-    public SQLSetStatement parseAlter() {
+
+    public SQLStatement parseAlter() {
         accept(Token.ALTER);
+
+        boolean ignore = false;
+
+        if (identifierEquals("IGNORE")) {
+            ignore = true;
+            lexer.nextToken();
+        }
+
+        if (lexer.token() == Token.TABLE) {
+            lexer.nextToken();
+
+            MySqlAlterTableStatement stmt = new MySqlAlterTableStatement();
+            stmt.setIgnore(ignore);
+            stmt.setName(this.exprParser.name());
+
+            for (;;) {
+                if (identifierEquals("ADD")) {
+                    lexer.nextToken();
+
+                    if (identifierEquals("COLUMN")) {
+                        lexer.nextToken();
+                        MySqlAlterTableAddColumn item = new MySqlAlterTableAddColumn();
+                        SQLColumnDefinition columnDef = this.exprParser.parseColumn();
+                        item.getColumns().add(columnDef);
+                        if (identifierEquals("AFTER")) {
+                            lexer.nextToken();
+                            item.setAfter(this.exprParser.name());
+                        }
+                        stmt.getItems().add(item);
+                    } else {
+                        throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                    }
+                } else if (identifierEquals("ALTER")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("CHANGE")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("MODIFY")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (lexer.token() == Token.DROP) {
+                    lexer.nextToken();
+                    if (identifierEquals("COLUMN")) {
+                        lexer.nextToken();
+                    }
+                    SQLAlterTableDropColumnItem item = new SQLAlterTableDropColumnItem();
+                    item.setColumnName(this.exprParser.name());
+                    stmt.getItems().add(item);
+                } else if (identifierEquals("DISABLE")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("ENABLE")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("RENAME")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (lexer.token() == Token.ORDER) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("CONVERT")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (lexer.token() == Token.DEFAULT) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("DISCARD")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("IMPORT")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("FORCE")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("TRUNCATE")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("COALESCE")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+
+                } else if (identifierEquals("REORGANIZE")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("EXCHANGE")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("ANALYZE")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("CHECK")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("OPTIMIZE")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("REBUILD")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("REPAIR")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else if (identifierEquals("REMOVE")) {
+                    throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
+                } else {
+                    break;
+                }
+            }
+
+            return stmt;
+        }
         throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
     }
 }

src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlASTVisitor.java

@@ -25,6 +25,8 @@ import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlMatchAgainstExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlOutFileExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlUserName;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.CobarShowStatus;
+import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlAlterTableAddColumn;
+import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlAlterTableStatement;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlBinlogStatement;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlCommitStatement;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlCreateUserStatement;
@@ -288,132 +290,140 @@ public interface MySqlASTVisitor extends SQLASTVisitor {
     boolean visit(MySqlShowContributorsStatement x);
 
     void endVisit(MySqlShowContributorsStatement x);
-    
+
     boolean visit(MySqlShowCreateDatabaseStatement x);
-    
+
     void endVisit(MySqlShowCreateDatabaseStatement x);
-    
+
     boolean visit(MySqlShowCreateEventStatement x);
-    
+
     void endVisit(MySqlShowCreateEventStatement x);
-    
+
     boolean visit(MySqlShowCreateFunctionStatement x);
-    
+
     void endVisit(MySqlShowCreateFunctionStatement x);
-    
+
     boolean visit(MySqlShowCreateProcedureStatement x);
-    
+
     void endVisit(MySqlShowCreateProcedureStatement x);
-    
+
     boolean visit(MySqlShowCreateTableStatement x);
-    
+
     void endVisit(MySqlShowCreateTableStatement x);
-    
+
     boolean visit(MySqlShowCreateTriggerStatement x);
-    
+
     void endVisit(MySqlShowCreateTriggerStatement x);
-    
+
     boolean visit(MySqlShowCreateViewStatement x);
-    
+
     void endVisit(MySqlShowCreateViewStatement x);
-    
+
     boolean visit(MySqlShowEngineStatement x);
-    
+
     void endVisit(MySqlShowEngineStatement x);
-    
+
     boolean visit(MySqlShowEnginesStatement x);
-    
+
     void endVisit(MySqlShowEnginesStatement x);
-    
+
     boolean visit(MySqlShowErrorsStatement x);
-    
+
     void endVisit(MySqlShowErrorsStatement x);
-    
+
     boolean visit(MySqlShowEventsStatement x);
-    
+
     void endVisit(MySqlShowEventsStatement x);
-    
+
     boolean visit(MySqlShowFunctionCodeStatement x);
-    
+
     void endVisit(MySqlShowFunctionCodeStatement x);
-    
+
     boolean visit(MySqlShowFunctionStatusStatement x);
-    
+
     void endVisit(MySqlShowFunctionStatusStatement x);
-    
+
     boolean visit(MySqlShowGrantsStatement x);
-    
+
     void endVisit(MySqlShowGrantsStatement x);
-    
+
     boolean visit(MySqlUserName x);
-    
+
     void endVisit(MySqlUserName x);
-    
+
     boolean visit(MySqlShowIndexesStatement x);
-    
+
     void endVisit(MySqlShowIndexesStatement x);
-    
+
     boolean visit(MySqlShowKeysStatement x);
-    
+
     void endVisit(MySqlShowKeysStatement x);
-    
+
     boolean visit(MySqlShowMasterStatusStatement x);
-    
+
     void endVisit(MySqlShowMasterStatusStatement x);
-    
+
     boolean visit(MySqlShowOpenTablesStatement x);
-    
+
     void endVisit(MySqlShowOpenTablesStatement x);
-    
+
     boolean visit(MySqlShowPluginsStatement x);
-    
+
     void endVisit(MySqlShowPluginsStatement x);
-    
+
     boolean visit(MySqlShowPrivilegesStatement x);
-    
+
     void endVisit(MySqlShowPrivilegesStatement x);
-    
+
     boolean visit(MySqlShowProcedureCodeStatement x);
-    
+
     void endVisit(MySqlShowProcedureCodeStatement x);
-    
+
     boolean visit(MySqlShowProcedureStatusStatement x);
-    
+
     void endVisit(MySqlShowProcedureStatusStatement x);
-    
+
     boolean visit(MySqlShowProcessListStatement x);
-    
+
     void endVisit(MySqlShowProcessListStatement x);
-    
+
     boolean visit(MySqlShowProfileStatement x);
-    
+
     void endVisit(MySqlShowProfileStatement x);
-    
+
     boolean visit(MySqlShowProfilesStatement x);
-    
+
     void endVisit(MySqlShowProfilesStatement x);
-    
+
     boolean visit(MySqlShowRelayLogEventsStatement x);
-    
+
     void endVisit(MySqlShowRelayLogEventsStatement x);
-    
+
     boolean visit(MySqlShowSlaveHostsStatement x);
-    
+
     void endVisit(MySqlShowSlaveHostsStatement x);
-    
+
     boolean visit(MySqlShowSlaveStatusStatement x);
-    
+
     void endVisit(MySqlShowSlaveStatusStatement x);
-    
+
     boolean visit(MySqlShowTableStatusStatement x);
-    
+
     void endVisit(MySqlShowTableStatusStatement x);
-    
+
     boolean visit(MySqlShowTriggersStatement x);
-    
+
     void endVisit(MySqlShowTriggersStatement x);
-    
+
     boolean visit(MySqlShowVariantsStatement x);
-    
+
     void endVisit(MySqlShowVariantsStatement x);
+
+    boolean visit(MySqlAlterTableStatement x);
+
+    void endVisit(MySqlAlterTableStatement x);
+    
+    boolean visit(MySqlAlterTableAddColumn x);
+    
+    void endVisit(MySqlAlterTableAddColumn x);
 }

src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlASTVisitorAdapter.java

@@ -10,6 +10,8 @@ import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlMatchAgainstExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlOutFileExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlUserName;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.CobarShowStatus;
+import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlAlterTableAddColumn;
+import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlAlterTableStatement;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlBinlogStatement;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlCommitStatement;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlCreateUserStatement;
@@ -904,4 +906,24 @@ public class MySqlASTVisitorAdapter extends SQLASTVisitorAdapter implements
     public void endVisit(MySqlShowVariantsStatement x) {
         
     }
+
+    @Override
+    public boolean visit(MySqlAlterTableStatement x) {
+        return true;
+    }
+
+    @Override
+    public void endVisit(MySqlAlterTableStatement x) {
+        
+    }
+
+    @Override
+    public boolean visit(MySqlAlterTableAddColumn x) {
+        return true;
+    }
+
+    @Override
+    public void endVisit(MySqlAlterTableAddColumn x) {
+        
+    }
 }

src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlOutputVisitor.java

@@ -22,7 +22,9 @@ import com.alibaba.druid.sql.ast.SQLExpr;
 import com.alibaba.druid.sql.ast.SQLSetQuantifier;
 import com.alibaba.druid.sql.ast.expr.SQLCharExpr;
 import com.alibaba.druid.sql.ast.expr.SQLMethodInvokeExpr;
+import com.alibaba.druid.sql.ast.expr.SQLNullExpr;
 import com.alibaba.druid.sql.ast.expr.SQLVariantRefExpr;
+import com.alibaba.druid.sql.ast.statement.SQLAlterTableItem;
 import com.alibaba.druid.sql.ast.statement.SQLCharactorDataType;
 import com.alibaba.druid.sql.ast.statement.SQLColumnConstraint;
 import com.alibaba.druid.sql.ast.statement.SQLColumnDefinition;
@@ -40,6 +42,8 @@ import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlMatchAgainstExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlOutFileExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlUserName;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.CobarShowStatus;
+import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlAlterTableAddColumn;
+import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlAlterTableStatement;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlBinlogStatement;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlCommitStatement;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlCreateTableStatement;
@@ -250,8 +254,12 @@ public class MySqlOutputVisitor extends SQLASTOutputVisitor implements MySqlASTV
         x.getDataType().accept(this);
 
         if (x.getDefaultExpr() != null) {
-            print(" DEFAULT ");
-            x.getDefaultExpr().accept(this);
+            if (x.getDefaultExpr() instanceof SQLNullExpr) {
+                print(" NULL");
+            } else {
+                print(" DEFAULT");
+                x.getDefaultExpr().accept(this);
+            }
         }
 
         if (mysqlColumn != null && mysqlColumn.isAutoIncrement()) {
@@ -2155,12 +2163,50 @@ public class MySqlOutputVisitor extends SQLASTOutputVisitor implements MySqlASTV
             x.getWhere().setParent(x);
             x.getWhere().accept(this);
         }
-        
+
         return false;
     }
 
     @Override
     public void endVisit(MySqlShowVariantsStatement x) {
-        
+
+    }
+
+    @Override
+    public boolean visit(MySqlAlterTableStatement x) {
+        if (x.isIgnore()) {
+            print("ALTER IGNORE TABLE ");
+        } else {
+            print("ALTER TABLE ");
+        }
+        x.getName().accept(this);
+        incrementIndent();
+        for (SQLAlterTableItem item : x.getItems()) {
+            println();
+            item.accept(this);
+        }
+        decrementIndent();
+        return false;
+    }
+
+    @Override
+    public void endVisit(MySqlAlterTableStatement x) {
+
+    }
+
+    @Override
+    public boolean visit(MySqlAlterTableAddColumn x) {
+        print("ADD COLUMN ");
+        printAndAccept(x.getColumns(), ", ");
+        if (x.getAfter() != null) {
+            print(" AFTER ");
+            x.getAfter().accept(this);
+        }
+        return false;
+    }
+
+    @Override
+    public void endVisit(MySqlAlterTableAddColumn x) {
+
     }
 }

src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlSchemaStatVisitor.java

@@ -19,6 +19,8 @@ import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlMatchAgainstExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlOutFileExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlUserName;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.CobarShowStatus;
+import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlAlterTableAddColumn;
+import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlAlterTableStatement;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlBinlogStatement;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlCommitStatement;
 import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlCreateUserStatement;
@@ -967,4 +969,24 @@ public class MySqlSchemaStatVisitor extends SchemaStatVisitor implements MySqlAS
     public void endVisit(MySqlShowVariantsStatement x) {
         
     }
+
+    @Override
+    public boolean visit(MySqlAlterTableStatement x) {
+        return false;
+    }
+
+    @Override
+    public void endVisit(MySqlAlterTableStatement x) {
+        
+    }
+
+    @Override
+    public boolean visit(MySqlAlterTableAddColumn x) {
+        return false;
+    }
+
+    @Override
+    public void endVisit(MySqlAlterTableAddColumn x) {
+        
+    }
 }

src/main/java/com/alibaba/druid/sql/parser/SQLExprParser.java

@@ -1163,6 +1163,12 @@ public class SQLExprParser extends SQLParser {
             column.getConstaints().add(new NotNullConstraint());
             return parseColumnRest(column);
         }
+        
+        if (lexer.token() == Token.NULL) {
+            lexer.nextToken();
+            column.setDefaultExpr(new SQLNullExpr());
+            return parseColumnRest(column);
+        }
 
         return column;
     }

src/main/java/com/alibaba/druid/sql/parser/SQLStatementParser.java

@@ -164,7 +164,7 @@ public class SQLStatementParser extends SQLParser {
         return stmt;
     }
     
-    public SQLSetStatement parseAlter() {
+    public SQLStatement parseAlter() {
         accept(Token.ALTER);
         throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
     }

src/main/java/com/alibaba/druid/sql/visitor/SQLASTOutputVisitor.java

@@ -69,6 +69,7 @@ import com.alibaba.druid.sql.ast.statement.SQLInsertStatement.ValuesClause;
 import com.alibaba.druid.sql.ast.statement.SQLJoinTableSource;
 import com.alibaba.druid.sql.ast.statement.SQLJoinTableSource.JoinType;
 import com.alibaba.druid.sql.ast.statement.SQLAlterTableAddColumn;
+import com.alibaba.druid.sql.ast.statement.SQLAlterTableDropColumnItem;
 import com.alibaba.druid.sql.ast.statement.SQLSelect;
 import com.alibaba.druid.sql.ast.statement.SQLSelectGroupByClause;
 import com.alibaba.druid.sql.ast.statement.SQLSelectItem;
@@ -1013,6 +1014,13 @@ public class SQLASTOutputVisitor extends SQLASTVisitorAdapter {
         print(")");
         return false;
     }
+    
+    @Override
+    public boolean visit(SQLAlterTableDropColumnItem x) {
+        print("DROP COLUMN ");
+        x.getColumnName().accept(this);
+        return false;
+    }
 
     @Override
     public void endVisit(SQLAlterTableAddColumn x) {

src/main/java/com/alibaba/druid/sql/visitor/SQLASTVisitor.java

@@ -52,6 +52,7 @@ import com.alibaba.druid.sql.ast.expr.SQLUnaryExpr;
 import com.alibaba.druid.sql.ast.expr.SQLVariantRefExpr;
 import com.alibaba.druid.sql.ast.statement.NotNullConstraint;
 import com.alibaba.druid.sql.ast.statement.SQLAlterTableAddColumn;
+import com.alibaba.druid.sql.ast.statement.SQLAlterTableDropColumnItem;
 import com.alibaba.druid.sql.ast.statement.SQLAssignItem;
 import com.alibaba.druid.sql.ast.statement.SQLCallStatement;
 import com.alibaba.druid.sql.ast.statement.SQLColumnDefinition;
@@ -340,4 +341,8 @@ public interface SQLASTVisitor {
     boolean visit(SQLAlterTableAddColumn x);
 
     void endVisit(SQLAlterTableAddColumn x);
+    
+    boolean visit(SQLAlterTableDropColumnItem x);
+    
+    void endVisit(SQLAlterTableDropColumnItem x);
 }

src/main/java/com/alibaba/druid/sql/visitor/SQLASTVisitorAdapter.java

@@ -51,6 +51,7 @@ import com.alibaba.druid.sql.ast.expr.SQLSomeExpr;
 import com.alibaba.druid.sql.ast.expr.SQLUnaryExpr;
 import com.alibaba.druid.sql.ast.expr.SQLVariantRefExpr;
 import com.alibaba.druid.sql.ast.statement.NotNullConstraint;
+import com.alibaba.druid.sql.ast.statement.SQLAlterTableDropColumnItem;
 import com.alibaba.druid.sql.ast.statement.SQLAssignItem;
 import com.alibaba.druid.sql.ast.statement.SQLCallStatement;
 import com.alibaba.druid.sql.ast.statement.SQLColumnDefinition;
@@ -595,4 +596,14 @@ public class SQLASTVisitorAdapter implements SQLASTVisitor {
     public void endVisit(SQLAlterTableAddColumn x) {
 
     }
+
+    @Override
+    public boolean visit(SQLAlterTableDropColumnItem x) {
+        return true;
+    }
+
+    @Override
+    public void endVisit(SQLAlterTableDropColumnItem x) {
+        
+    }
 }

src/test/java/com/alibaba/druid/bvt/sql/cobar/DDLParserTest.java

@@ -25,7 +25,7 @@ public class DDLParserTest extends TestCase {
         String output = SQLUtils.toMySqlString(stmt);
         Assert.assertEquals("TRUNCATE TABLE tb1", output);
     }
-    
+
     public void testTruncate_1() throws Exception {
         String sql = "Truncate tb1";
         MySqlStatementParser parser = new MySqlStatementParser(sql);
@@ -34,116 +34,145 @@ public class DDLParserTest extends TestCase {
         String output = SQLUtils.toMySqlString(stmt);
         Assert.assertEquals("TRUNCATE TABLE tb1", output);
     }
-    
-    public void testAlterTable0() throws Exception {
+
+    public void testAlterTable_0() throws Exception {
         String sql = "alTer ignore table tb_name";
         MySqlStatementParser parser = new MySqlStatementParser(sql);
         SQLStatement stmt = parser.parseStatementList().get(0);
         parser.match(Token.EOF);
         String output = SQLUtils.toMySqlString(stmt);
-        Assert.assertEquals("ALTER ignore table tb_name", output);
+        Assert.assertEquals("ALTER IGNORE TABLE tb_name", output);
     }
 
-//    public void testDDLStmt() throws Exception {
-//        String sql = "alTer ignore table tb_name";
-//        SQLLexer lexer = new SQLLexer(sql);
-//        DDLParser parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        DDLStatement dst = parser.ddlStmt();
-//
-//        sql = "alTeR table tb_name";
-//        lexer = new SQLLexer(sql);
-//        parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        dst = parser.ddlStmt();
-//
-//        sql = "crEate temporary tabLe if not exists tb_name";
-//        lexer = new SQLLexer(sql);
-//        parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        dst = parser.ddlStmt();
-//
-//        sql = "crEate tabLe if not exists tb_name";
-//        lexer = new SQLLexer(sql);
-//        parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        dst = parser.ddlStmt();
-//
-//        sql = "crEate temporary tabLe tb_name";
-//        lexer = new SQLLexer(sql);
-//        parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        dst = parser.ddlStmt();
-//
-//        sql = "crEate unique index index_name on tb(col(id)) desc";
-//        lexer = new SQLLexer(sql);
-//        parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        dst = parser.ddlStmt();
-//
-//        sql = "crEate fulltext index index_name on tb(col(id))";
-//        lexer = new SQLLexer(sql);
-//        parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        dst = parser.ddlStmt();
-//
-//        sql = "crEate spatial index index_name on tb(col(id))";
-//        lexer = new SQLLexer(sql);
-//        parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        dst = parser.ddlStmt();
-//
-//        sql = "crEate index index_name using hash on tb(col(id))";
-//        lexer = new SQLLexer(sql);
-//        parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        dst = parser.ddlStmt();
-//
-//        sql = "drop index index_name on tb1";
-//        lexer = new SQLLexer(sql);
-//        parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        dst = parser.ddlStmt();
-//        String output = output2MySQL(dst, sql);
-//        Assert.assertEquals("DROP INDEX index_name ON tb1", output);
-//
-//        sql = "drop temporary tabLe if exists tb1,tb2,tb3 restrict";
-//        lexer = new SQLLexer(sql);
-//        parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        dst = parser.ddlStmt();
-//        output = output2MySQL(dst, sql);
-//        Assert.assertEquals("DROP TEMPORARY TABLE IF EXISTS tb1, tb2, tb3 RESTRICT", output);
-//
-//        sql = "drop temporary tabLe if exists tb1,tb2,tb3 cascade";
-//        lexer = new SQLLexer(sql);
-//        parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        dst = parser.ddlStmt();
-//        output = output2MySQL(dst, sql);
-//        Assert.assertEquals("DROP TEMPORARY TABLE IF EXISTS tb1, tb2, tb3 CASCADE", output);
-//
-//        sql = "drop temporary tabLe if exists tb1 cascade";
-//        lexer = new SQLLexer(sql);
-//        parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        dst = parser.ddlStmt();
-//        output = output2MySQL(dst, sql);
-//        Assert.assertEquals("DROP TEMPORARY TABLE IF EXISTS tb1 CASCADE", output);
-//
-//        sql = "drop tabLe if exists tb1 cascade";
-//        lexer = new SQLLexer(sql);
-//        parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        dst = parser.ddlStmt();
-//        output = output2MySQL(dst, sql);
-//        Assert.assertEquals("DROP TABLE IF EXISTS tb1 CASCADE", output);
-//
-//        sql = "drop temporary tabLe tb1 cascade";
-//        lexer = new SQLLexer(sql);
-//        parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        dst = parser.ddlStmt();
-//        output = output2MySQL(dst, sql);
-//        Assert.assertEquals("DROP TEMPORARY TABLE tb1 CASCADE", output);
-//
-//        sql = "rename table tb1 to ntb1,tb2 to ntb2";
-//        lexer = new SQLLexer(sql);
-//        parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        dst = parser.ddlStmt();
-//        output = output2MySQL(dst, sql);
-//        Assert.assertEquals("RENAME TABLE tb1 TO ntb1, tb2 TO ntb2", output);
-//
-//        sql = "rename table tb1 to ntb1";
-//        lexer = new SQLLexer(sql);
-//        parser = new DDLParser(lexer, new SQLExprParser(lexer));
-//        dst = parser.ddlStmt();
-//        output = output2MySQL(dst, sql);
-//        Assert.assertEquals("RENAME TABLE tb1 TO ntb1", output);
-//    }
+    public void testAlterTable_1() throws Exception {
+        String sql = "alTer table tb_name";
+        MySqlStatementParser parser = new MySqlStatementParser(sql);
+        SQLStatement stmt = parser.parseStatementList().get(0);
+        parser.match(Token.EOF);
+        String output = SQLUtils.toMySqlString(stmt);
+        Assert.assertEquals("ALTER TABLE tb_name", output);
+    }
+
+    public void testAlterTable_2() throws Exception {
+        String sql = "ALTER TABLE `test`.`tb1` ADD COLUMN `name` VARCHAR(45) NULL  AFTER `fid` ;";
+        MySqlStatementParser parser = new MySqlStatementParser(sql);
+        SQLStatement stmt = parser.parseStatementList().get(0);
+        parser.match(Token.EOF);
+        String output = SQLUtils.toMySqlString(stmt);
+        Assert.assertEquals("ALTER TABLE `test`.`tb1`" + //
+                            "\n\tADD COLUMN `name` VARCHAR(45) NULL AFTER `fid`", output);
+    }
+    
+    public void testAlterTable_3() throws Exception {
+        String sql = "ALTER TABLE `test`.`tb1` DROP COLUMN `name` ;";
+        MySqlStatementParser parser = new MySqlStatementParser(sql);
+        SQLStatement stmt = parser.parseStatementList().get(0);
+        parser.match(Token.EOF);
+        String output = SQLUtils.toMySqlString(stmt);
+        Assert.assertEquals("ALTER TABLE `test`.`tb1`" + //
+                "\n\tDROP COLUMN `name`", output);
+    }
+
+    // public void testDDLStmt() throws Exception {
+    // String sql = "alTer ignore table tb_name";
+    // SQLLexer lexer = new SQLLexer(sql);
+    // DDLParser parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // DDLStatement dst = parser.ddlStmt();
+    //
+    // sql = "alTeR table tb_name";
+    // lexer = new SQLLexer(sql);
+    // parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // dst = parser.ddlStmt();
+    //
+    // sql = "crEate temporary tabLe if not exists tb_name";
+    // lexer = new SQLLexer(sql);
+    // parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // dst = parser.ddlStmt();
+    //
+    // sql = "crEate tabLe if not exists tb_name";
+    // lexer = new SQLLexer(sql);
+    // parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // dst = parser.ddlStmt();
+    //
+    // sql = "crEate temporary tabLe tb_name";
+    // lexer = new SQLLexer(sql);
+    // parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // dst = parser.ddlStmt();
+    //
+    // sql = "crEate unique index index_name on tb(col(id)) desc";
+    // lexer = new SQLLexer(sql);
+    // parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // dst = parser.ddlStmt();
+    //
+    // sql = "crEate fulltext index index_name on tb(col(id))";
+    // lexer = new SQLLexer(sql);
+    // parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // dst = parser.ddlStmt();
+    //
+    // sql = "crEate spatial index index_name on tb(col(id))";
+    // lexer = new SQLLexer(sql);
+    // parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // dst = parser.ddlStmt();
+    //
+    // sql = "crEate index index_name using hash on tb(col(id))";
+    // lexer = new SQLLexer(sql);
+    // parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // dst = parser.ddlStmt();
+    //
+    // sql = "drop index index_name on tb1";
+    // lexer = new SQLLexer(sql);
+    // parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // dst = parser.ddlStmt();
+    // String output = output2MySQL(dst, sql);
+    // Assert.assertEquals("DROP INDEX index_name ON tb1", output);
+    //
+    // sql = "drop temporary tabLe if exists tb1,tb2,tb3 restrict";
+    // lexer = new SQLLexer(sql);
+    // parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // dst = parser.ddlStmt();
+    // output = output2MySQL(dst, sql);
+    // Assert.assertEquals("DROP TEMPORARY TABLE IF EXISTS tb1, tb2, tb3 RESTRICT", output);
+    //
+    // sql = "drop temporary tabLe if exists tb1,tb2,tb3 cascade";
+    // lexer = new SQLLexer(sql);
+    // parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // dst = parser.ddlStmt();
+    // output = output2MySQL(dst, sql);
+    // Assert.assertEquals("DROP TEMPORARY TABLE IF EXISTS tb1, tb2, tb3 CASCADE", output);
+    //
+    // sql = "drop temporary tabLe if exists tb1 cascade";
+    // lexer = new SQLLexer(sql);
+    // parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // dst = parser.ddlStmt();
+    // output = output2MySQL(dst, sql);
+    // Assert.assertEquals("DROP TEMPORARY TABLE IF EXISTS tb1 CASCADE", output);
+    //
+    // sql = "drop tabLe if exists tb1 cascade";
+    // lexer = new SQLLexer(sql);
+    // parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // dst = parser.ddlStmt();
+    // output = output2MySQL(dst, sql);
+    // Assert.assertEquals("DROP TABLE IF EXISTS tb1 CASCADE", output);
+    //
+    // sql = "drop temporary tabLe tb1 cascade";
+    // lexer = new SQLLexer(sql);
+    // parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // dst = parser.ddlStmt();
+    // output = output2MySQL(dst, sql);
+    // Assert.assertEquals("DROP TEMPORARY TABLE tb1 CASCADE", output);
+    //
+    // sql = "rename table tb1 to ntb1,tb2 to ntb2";
+    // lexer = new SQLLexer(sql);
+    // parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // dst = parser.ddlStmt();
+    // output = output2MySQL(dst, sql);
+    // Assert.assertEquals("RENAME TABLE tb1 TO ntb1, tb2 TO ntb2", output);
+    //
+    // sql = "rename table tb1 to ntb1";
+    // lexer = new SQLLexer(sql);
+    // parser = new DDLParser(lexer, new SQLExprParser(lexer));
+    // dst = parser.ddlStmt();
+    // output = output2MySQL(dst, sql);
+    // Assert.assertEquals("RENAME TABLE tb1 TO ntb1", output);
+    // }
 }