improved sql parser.

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

@@ -52,4 +52,8 @@ public class SQLCharExpr extends SQLTextLiteralExpr implements SQLValuableExpr{
     public String toString() {
         return SQLUtils.toSQLString(this);
     }
+
+    public SQLCharExpr clone() {
+        return new SQLCharExpr(this.text);
+    }
 }

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

@@ -100,4 +100,15 @@ public class SQLExistsExpr extends SQLExprImpl implements Serializable {
         }
         return true;
     }
+
+    public SQLExistsExpr clone () {
+        SQLExistsExpr x = new SQLExistsExpr();
+
+        x.not = not;
+        if (subQuery != null) {
+            x.setSubQuery(subQuery.clone());
+        }
+
+        return x;
+    }
 }

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

@@ -15,6 +15,7 @@
  */
 package com.alibaba.druid.sql.ast.expr;
 
+import com.alibaba.druid.sql.SQLUtils;
 import com.alibaba.druid.sql.ast.SQLExprImpl;
 import com.alibaba.druid.sql.ast.SQLName;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
@@ -102,6 +103,28 @@ public class SQLIdentifierExpr extends SQLExprImpl implements SQLName {
         return true;
     }
 
+    public boolean equalsIgnoreCase(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj == null) {
+            return false;
+        }
+        if (!(obj instanceof SQLIdentifierExpr)) {
+            return false;
+        }
+        SQLIdentifierExpr other = (SQLIdentifierExpr) obj;
+        if (name == null) {
+            if (other.name != null) {
+                return false;
+            }
+
+        } else if (!SQLUtils.normalize(name).equalsIgnoreCase(SQLUtils.normalize(other.name))) {
+            return false;
+        }
+        return true;
+    }
+
     public String toString() {
         return this.name;
     }

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

@@ -71,7 +71,14 @@ public abstract class SQLInsertInto extends SQLObjectImpl {
         return query;
     }
 
+    public void setQuery(SQLSelectQuery query) {
+        this.setQuery(new SQLSelect(query));
+    }
+
     public void setQuery(SQLSelect query) {
+        if (query != null) {
+            query.setParent(this);
+        }
         this.query = query;
     }
 

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

@@ -154,7 +154,10 @@ public class SQLSelect extends SQLObjectImpl {
         SQLSelect x = new SQLSelect();
 
         x.withSubQuery = this.withSubQuery;
-        x.query = this.query;
+        if (query != null) {
+            x.setQuery(query.clone());
+        }
+
         if (orderBy != null) {
             x.setOrderBy(this.orderBy.clone());
         }

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

@@ -21,4 +21,5 @@ public interface SQLSelectQuery extends SQLObject {
     boolean isBracket();
     void setBracket(boolean bracket);
 
+    SQLSelectQuery clone();
 }

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

@@ -20,6 +20,7 @@ import java.util.List;
 
 import com.alibaba.druid.sql.SQLUtils;
 import com.alibaba.druid.sql.ast.*;
+import com.alibaba.druid.sql.ast.expr.SQLBinaryOpExpr;
 import com.alibaba.druid.sql.ast.expr.SQLIdentifierExpr;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
@@ -439,4 +440,12 @@ public class SQLSelectQueryBlock extends SQLObjectImpl implements SQLSelectQuery
 
         return null;
     }
+
+    public void addCondition(SQLExpr expr) {
+        if (expr == null) {
+            return;
+        }
+
+        this.setWhere(SQLBinaryOpExpr.and(where, expr));
+    }
 }

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

@@ -43,6 +43,12 @@ public class SQLUnionQuery extends SQLObjectImpl implements SQLSelectQuery {
 
     }
 
+    public SQLUnionQuery(SQLSelectQuery left, SQLUnionOperator operator, SQLSelectQuery right){
+        this.setLeft(left);
+        this.operator = operator;
+        this.setRight(right);
+    }
+
     public SQLSelectQuery getLeft() {
         return left;
     }
@@ -106,4 +112,27 @@ public class SQLUnionQuery extends SQLObjectImpl implements SQLSelectQuery {
     public void setBracket(boolean bracket) {
         this.bracket = bracket;
     }
+
+    public SQLUnionQuery clone() {
+        SQLUnionQuery x = new SQLUnionQuery();
+
+        x.bracket = bracket;
+        if (left != null) {
+            x.setLeft(left.clone());
+        }
+        if (right != null) {
+            x.setRight(right.clone());
+        }
+        x.operator = operator;
+
+        if (orderBy != null) {
+            x.setOrderBy(orderBy.clone());
+        }
+
+        if (limit != null) {
+            x.setLimit(limit.clone());
+        }
+
+        return x;
+    }
 }