improve mysql ddl parser support

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

@@ -180,7 +180,7 @@ public class MySqlCreateTableParser extends SQLCreateTableParser {
                     if (lexer.token() == Token.EQ) {
                         lexer.nextToken();
                     }
-                    stmt.getTableOptions().put("CHARACTER SET", lexer.stringVal());
+                    stmt.getTableOptions().put("CHARSET", lexer.stringVal());
                     lexer.nextToken();
                 }
             }

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

@@ -2212,7 +2212,7 @@ public class MySqlStatementParser extends SQLStatementParser {
                         }
                         stmt.getItems().add(item);
                     }
-                } else if (identifierEquals("ALTER")) {
+                } else if (lexer.token() == Token.ALTER) {
                     throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
                 } else if (identifierEquals("CHANGE")) {
                     lexer.nextToken();

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

@@ -19,6 +19,8 @@ import java.util.Map;
 
 import com.alibaba.druid.sql.ast.SQLName;
 import com.alibaba.druid.sql.ast.expr.SQLIdentifierExpr;
+import com.alibaba.druid.sql.ast.statement.SQLAlterTableAddColumn;
+import com.alibaba.druid.sql.ast.statement.SQLAlterTableItem;
 import com.alibaba.druid.sql.ast.statement.SQLCreateTableStatement;
 import com.alibaba.druid.sql.ast.statement.SQLDropTableStatement;
 import com.alibaba.druid.sql.ast.statement.SQLExprTableSource;
@@ -245,8 +247,7 @@ public class MySqlSchemaStatVisitor extends SchemaStatVisitor implements MySqlAS
 
     @Override
     public boolean visit(MySqlKey x) {
-
-        return true;
+        return false;
     }
 
     @Override
@@ -1012,6 +1013,17 @@ public class MySqlSchemaStatVisitor extends SchemaStatVisitor implements MySqlAS
 
     @Override
     public boolean visit(MySqlAlterTableStatement x) {
+        String tableName = x.getName().toString();
+        TableStat stat = getTableStat(tableName);
+        stat.incrementAlterCount();
+
+        setCurrentTable(x, tableName);
+
+        for (SQLAlterTableItem item : x.getItems()) {
+            item.setParent(x);
+            item.accept(this);
+        }
+
         return false;
     }
 
@@ -1022,7 +1034,7 @@ public class MySqlSchemaStatVisitor extends SchemaStatVisitor implements MySqlAS
 
     @Override
     public boolean visit(MySqlAlterTableAddColumn x) {
-        return false;
+        return visit((SQLAlterTableAddColumn) x);
     }
 
     @Override
@@ -1209,4 +1221,5 @@ public class MySqlSchemaStatVisitor extends SchemaStatVisitor implements MySqlAS
     public void endVisit(MySqlAlterTableAddUnique x) {
         
     }
+    
 }

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

@@ -994,7 +994,7 @@ public class SchemaStatVisitor extends SQLASTVisitorAdapter {
     public boolean visit(SQLCurrentOfCursorExpr x) {
         return false;
     }
-
+    
     @Override
     public boolean visit(SQLAlterTableAddColumn x) {
         SQLAlterTableStatement stmt = (SQLAlterTableStatement) x.getParent();

src/main/java/com/alibaba/druid/stat/TableStat.java

@@ -445,7 +445,7 @@ public class TableStat {
     }
 
     public static enum Mode {
-        Insert(1), Update(2), Delete(4), Select(8), Merge(16), Truncate(32);
+        Insert(1), Update(2), Delete(4), Select(8), Merge(16), Truncate(32), Alter(64);
 
         public final int mark;