diff --git a/src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/expr/MySqlCharExpr.java b/src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/expr/MySqlCharExpr.java
index 8289bf0d26..832eda9e59 100644
--- a/src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/expr/MySqlCharExpr.java
+++ b/src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/expr/MySqlCharExpr.java
@@ -16,6 +16,8 @@
 package com.alibaba.druid.sql.dialect.mysql.ast.expr;
 
 import com.alibaba.druid.sql.ast.expr.SQLCharExpr;
+import com.alibaba.druid.sql.dialect.mysql.visitor.MySqlASTVisitor;
+import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
 public class MySqlCharExpr extends SQLCharExpr implements MySqlExpr {
 
@@ -61,4 +63,19 @@ public class MySqlCharExpr extends SQLCharExpr implements MySqlExpr {
             buf.append(collate);
         }
     }
+    
+    @Override
+    protected void accept0(SQLASTVisitor visitor) {
+        if (visitor instanceof MySqlASTVisitor) {
+            accept0((MySqlASTVisitor) visitor);
+        } else {
+            visitor.visit(this);
+            visitor.endVisit(this);
+        }
+    }
+
+    public void accept0(MySqlASTVisitor visitor) {
+        visitor.visit(this);
+        visitor.endVisit(this);
+    }
 }
diff --git a/src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/statement/MySqlSelectGroupBy.java b/src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/statement/MySqlSelectGroupBy.java
index a6ff89c8ef..0ad071bb13 100644
--- a/src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/statement/MySqlSelectGroupBy.java
+++ b/src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/statement/MySqlSelectGroupBy.java
@@ -38,7 +38,12 @@ public class MySqlSelectGroupBy extends SQLSelectGroupByClause {
         if (visitor instanceof MySqlASTVisitor) {
             accept0((MySqlASTVisitor) visitor);
         } else {
-            throw new IllegalArgumentException("not support visitor type : " + visitor.getClass().getName());
+            if (visitor.visit(this)) {
+                acceptChild(visitor, this.getItems());
+                acceptChild(visitor, this.getHaving());
+            }
+
+            visitor.endVisit(this);
         }
     }
 
diff --git a/src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlASTVisitor.java b/src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlASTVisitor.java
index 069b2a7e4d..d77ebc7d3c 100644
--- a/src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlASTVisitor.java
+++ b/src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlASTVisitor.java
@@ -22,6 +22,7 @@ import com.alibaba.druid.sql.dialect.mysql.ast.MySqlPrimaryKey;
 import com.alibaba.druid.sql.dialect.mysql.ast.MySqlUseIndexHint;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlBinaryExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlBooleanExpr;
+import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlCharExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlExtractExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlIntervalExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlMatchAgainstExpr;
@@ -505,4 +506,8 @@ public interface MySqlASTVisitor extends SQLASTVisitor {
     boolean visit(MySqlHelpStatement x);
     
     void endVisit(MySqlHelpStatement x);
+    
+    boolean visit(MySqlCharExpr x);
+    
+    void endVisit(MySqlCharExpr x);
 }
diff --git a/src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlASTVisitorAdapter.java b/src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlASTVisitorAdapter.java
index 18f8b5435d..a389c55bfe 100644
--- a/src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlASTVisitorAdapter.java
+++ b/src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlASTVisitorAdapter.java
@@ -7,6 +7,7 @@ import com.alibaba.druid.sql.dialect.mysql.ast.MySqlPrimaryKey;
 import com.alibaba.druid.sql.dialect.mysql.ast.MySqlUseIndexHint;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlBinaryExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlBooleanExpr;
+import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlCharExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlExtractExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlIntervalExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlMatchAgainstExpr;
@@ -1101,4 +1102,14 @@ public class MySqlASTVisitorAdapter extends SQLASTVisitorAdapter implements
     public void endVisit(MySqlHelpStatement x) {
         
     }
+
+    @Override
+    public boolean visit(MySqlCharExpr x) {
+        return false;
+    }
+
+    @Override
+    public void endVisit(MySqlCharExpr x) {
+        
+    }
 }
diff --git a/src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlOutputVisitor.java b/src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlOutputVisitor.java
index 97a1c2aa0b..fee8400a20 100644
--- a/src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlOutputVisitor.java
+++ b/src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlOutputVisitor.java
@@ -486,16 +486,7 @@ public class MySqlOutputVisitor extends SQLASTOutputVisitor implements MySqlASTV
     }
 
     public boolean visit(SQLCharExpr x) {
-        if (x instanceof MySqlCharExpr) {
-            print(x.toString());
-        } else if ((x.getText() == null) || (x.getText().length() == 0)) {
-            print("NULL");
-        } else {
-            print("'");
-            print(x.getText().replaceAll("'", "''"));
-            print("'");
-        }
-
+        print(x.toString());
         return false;
     }
 
@@ -2603,4 +2594,15 @@ public class MySqlOutputVisitor extends SQLASTOutputVisitor implements MySqlASTV
     public void endVisit(MySqlHelpStatement x) {
         
     }
+
+    @Override
+    public boolean visit(MySqlCharExpr x) {
+        print(x.toString());
+        return false;
+    }
+
+    @Override
+    public void endVisit(MySqlCharExpr x) {
+        
+    }
 }
diff --git a/src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlSchemaStatVisitor.java b/src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlSchemaStatVisitor.java
index 7c6bf70f44..1fc9e5a9c8 100644
--- a/src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlSchemaStatVisitor.java
+++ b/src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlSchemaStatVisitor.java
@@ -18,6 +18,7 @@ import com.alibaba.druid.sql.dialect.mysql.ast.MySqlPrimaryKey;
 import com.alibaba.druid.sql.dialect.mysql.ast.MySqlUseIndexHint;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlBinaryExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlBooleanExpr;
+import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlCharExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlExtractExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlIntervalExpr;
 import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlMatchAgainstExpr;
@@ -1166,4 +1167,14 @@ public class MySqlSchemaStatVisitor extends SchemaStatVisitor implements MySqlAS
     public void endVisit(MySqlHelpStatement x) {
         
     }
+
+    @Override
+    public boolean visit(MySqlCharExpr x) {
+        return false;
+    }
+
+    @Override
+    public void endVisit(MySqlCharExpr x) {
+        
+    }
 }