improved sql parser.

src/main/java/com/alibaba/druid/sql/ast/SQLLimit.java

@@ -31,6 +31,11 @@ public class SQLLimit extends SQLObjectImpl {
         this.setRowCount(rowCount);
     }
 
+    public SQLLimit(SQLExpr offset, SQLExpr rowCount) {
+        this.setOffset(offset);
+        this.setRowCount(rowCount);
+    }
+
     private SQLExpr rowCount;
     private SQLExpr offset;
 

src/main/java/com/alibaba/druid/sql/ast/expr/SQLBinaryOpExpr.java

@@ -145,6 +145,10 @@ public class SQLBinaryOpExpr extends SQLExprImpl implements Serializable {
         return true;
     }
 
+    public SQLBinaryOpExpr clone() {
+        return new SQLBinaryOpExpr(left, operator, right, dbType);
+    }
+
     public String toString() {
         return SQLUtils.toSQLString(this, getDbType());
     }

src/main/java/com/alibaba/druid/sql/ast/expr/SQLIntegerExpr.java

@@ -82,4 +82,8 @@ public class SQLIntegerExpr extends SQLNumericLiteralExpr implements SQLValuable
     public Object getValue() {
         return this.number;
     }
+
+    public SQLIntegerExpr clone() {
+        return new SQLIntegerExpr(this.number);
+    }
 }

src/main/java/com/alibaba/druid/sql/ast/expr/SQLVariantRefExpr.java

@@ -104,4 +104,7 @@ public class SQLVariantRefExpr extends SQLExprImpl {
         this.global = global;
     }
 
+    public SQLVariantRefExpr clone() {
+        return new SQLVariantRefExpr(name, global);
+    }
 }

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

@@ -21,15 +21,29 @@ import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
 public class SQLAlterTableRename extends SQLObjectImpl implements SQLAlterTableItem {
 
-    protected SQLExpr to;
+    protected SQLExprTableSource to;
 
-    public SQLExpr getTo() {
+    public SQLAlterTableRename() {
+
+    }
+
+    public SQLAlterTableRename(SQLExpr to) {
+        this.setTo(to);
+    }
+
+    public SQLExprTableSource getTo() {
         return to;
     }
 
-    public void setTo(SQLExpr to) {
+    public void setTo(SQLExprTableSource to) {
+        if (to != null) {
+            to.setParent(this);
+        }
         this.to = to;
-        to.setParent(this);
+    }
+
+    public void setTo(SQLExpr to) {
+        this.setTo(new SQLExprTableSource(to));
     }
 
     @Override

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

@@ -20,9 +20,12 @@ import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 
+import com.alibaba.druid.sql.ast.SQLExpr;
 import com.alibaba.druid.sql.ast.SQLName;
 import com.alibaba.druid.sql.ast.SQLObject;
 import com.alibaba.druid.sql.ast.SQLStatementImpl;
+import com.alibaba.druid.sql.ast.expr.SQLIdentifierExpr;
+import com.alibaba.druid.sql.ast.expr.SQLPropertyExpr;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
 public class SQLAlterTableStatement extends SQLStatementImpl implements SQLDDLStatement {
@@ -118,6 +121,10 @@ public class SQLAlterTableStatement extends SQLStatementImpl implements SQLDDLSt
         this.tableSource = tableSource;
     }
 
+    public void setTableSource(SQLExpr table) {
+        this.setTableSource(new SQLExprTableSource(table));
+    }
+
     public SQLName getName() {
         if (getTableSource() == null) {
             return null;
@@ -141,4 +148,18 @@ public class SQLAlterTableStatement extends SQLStatementImpl implements SQLDDLSt
         }
         visitor.endVisit(this);
     }
+
+    public String getTableName() {
+        if (tableSource == null) {
+            return null;
+        }
+        SQLExpr expr = ((SQLExprTableSource) tableSource).getExpr();
+        if (expr instanceof SQLIdentifierExpr) {
+            return ((SQLIdentifierExpr) expr).getName();
+        } else if (expr instanceof SQLPropertyExpr) {
+            return ((SQLPropertyExpr) expr).getName();
+        }
+
+        return null;
+    }
 }

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

@@ -22,6 +22,8 @@ import com.alibaba.druid.sql.ast.SQLDataType;
 import com.alibaba.druid.sql.ast.SQLExpr;
 import com.alibaba.druid.sql.ast.SQLName;
 import com.alibaba.druid.sql.ast.SQLObjectImpl;
+import com.alibaba.druid.sql.ast.expr.SQLIdentifierExpr;
+import com.alibaba.druid.sql.ast.expr.SQLPropertyExpr;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
 public class SQLColumnDefinition extends SQLObjectImpl implements SQLTableElement {
@@ -259,4 +261,24 @@ public class SQLColumnDefinition extends SQLObjectImpl implements SQLTableElemen
         }
 
     }
+
+    public String computeAlias() {
+        String alias = null;
+
+        if (name instanceof SQLIdentifierExpr) {
+            alias = ((SQLIdentifierExpr) name).getName();
+        } else if (name instanceof SQLPropertyExpr) {
+            alias = ((SQLPropertyExpr) name).getName();
+        }
+
+        if (alias.length() > 2) {
+            char c0 = alias.charAt(0);
+            char x0 = alias.charAt(alias.length() - 1);
+            if ((c0 == '"' && x0 == '"') || (c0 == '`' && x0 == '`')) {
+                alias = alias.substring(1, alias.length() - 1);
+            }
+        }
+
+        return alias;
+    }
 }

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

@@ -18,8 +18,11 @@ package com.alibaba.druid.sql.ast.statement;
 import java.util.ArrayList;
 import java.util.List;
 
+import com.alibaba.druid.sql.ast.SQLExpr;
 import com.alibaba.druid.sql.ast.SQLName;
 import com.alibaba.druid.sql.ast.SQLStatementImpl;
+import com.alibaba.druid.sql.ast.expr.SQLIdentifierExpr;
+import com.alibaba.druid.sql.ast.expr.SQLPropertyExpr;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
 public class SQLCreateIndexStatement extends SQLStatementImpl implements SQLDDLStatement {
@@ -55,6 +58,19 @@ public class SQLCreateIndexStatement extends SQLStatementImpl implements SQLDDLS
         this.table = table;
     }
 
+    public String getTableName() {
+        if (table instanceof SQLExprTableSource) {
+            SQLExpr expr = ((SQLExprTableSource) table).getExpr();
+            if (expr instanceof SQLIdentifierExpr) {
+                return ((SQLIdentifierExpr) expr).getName();
+            } else if (expr instanceof SQLPropertyExpr) {
+                return ((SQLPropertyExpr) expr).getName();
+            }
+        }
+
+        return null;
+    }
+
     public List<SQLSelectOrderByItem> getItems() {
         return items;
     }

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

@@ -22,6 +22,7 @@ import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 public class SQLDropSequenceStatement extends SQLStatementImpl implements SQLDDLStatement {
 
     private SQLName name;
+    private boolean ifExists;
     
     public SQLDropSequenceStatement() {
         
@@ -47,4 +48,11 @@ public class SQLDropSequenceStatement extends SQLStatementImpl implements SQLDDL
         this.name = name;
     }
 
+    public boolean isIfExists() {
+        return ifExists;
+    }
+
+    public void setIfExists(boolean ifExists) {
+        this.ifExists = ifExists;
+    }
 }

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

@@ -22,7 +22,8 @@ import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 public class SQLDropTriggerStatement extends SQLStatementImpl implements SQLDDLStatement {
 
     private SQLName name;
-    
+    private boolean ifExists;
+
     public SQLDropTriggerStatement() {
         
     }
@@ -47,4 +48,11 @@ public class SQLDropTriggerStatement extends SQLStatementImpl implements SQLDDLS
         visitor.endVisit(this);
     }
 
+    public boolean isIfExists() {
+        return ifExists;
+    }
+
+    public void setIfExists(boolean ifExists) {
+        this.ifExists = ifExists;
+    }
 }

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

@@ -47,6 +47,9 @@ public class SQLIfStatement extends SQLStatementImpl {
     }
 
     public void setCondition(SQLExpr condition) {
+        if (condition != null) {
+            condition.setParent(this);
+        }
         this.condition = condition;
     }
 

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

@@ -26,7 +26,7 @@ public class SQLLoopStatement extends SQLStatementImpl {
 
     private String             labelName;
 
-    private List<SQLStatement> statements = new ArrayList<SQLStatement>();
+    private final List<SQLStatement> statements = new ArrayList<SQLStatement>();
 
     @Override
     public void accept0(SQLASTVisitor visitor) {
@@ -40,10 +40,6 @@ public class SQLLoopStatement extends SQLStatementImpl {
         return statements;
     }
 
-    public void setStatements(List<SQLStatement> statements) {
-        this.statements = statements;
-    }
-
     public String getLabelName() {
         return labelName;
     }

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

@@ -17,6 +17,8 @@ package com.alibaba.druid.sql.ast.statement;
 
 import com.alibaba.druid.sql.ast.SQLExpr;
 import com.alibaba.druid.sql.ast.SQLObjectImpl;
+import com.alibaba.druid.sql.ast.expr.SQLIdentifierExpr;
+import com.alibaba.druid.sql.ast.expr.SQLPropertyExpr;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
 public class SQLSelectItem extends SQLObjectImpl {
@@ -63,6 +65,27 @@ public class SQLSelectItem extends SQLObjectImpl {
         }
     }
 
+    public String computeAlias() {
+        String alias = this.getAlias();
+        if (alias == null) {
+            if (expr instanceof SQLIdentifierExpr) {
+                alias = ((SQLIdentifierExpr) expr).getName();
+            } else if (expr instanceof SQLPropertyExpr) {
+                alias = ((SQLPropertyExpr) expr).getName();
+            }
+        }
+
+        if (alias.length() > 2) {
+            char c0 = alias.charAt(0);
+            char x0 = alias.charAt(alias.length() - 1);
+            if ((c0 == '"' && x0 == '"') || (c0 == '`' && x0 == '`')) {
+                alias = alias.substring(1, alias.length() - 1);
+            }
+        }
+
+        return alias;
+    }
+
     public String getAlias() {
         return this.alias;
     }