enhance mysql sql parser support

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

@@ -17,6 +17,7 @@ package com.alibaba.druid.sql.ast.expr;
 
 import java.util.BitSet;
 
+import com.alibaba.druid.sql.ast.SQLExprImpl;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
 /**
@@ -28,7 +29,7 @@ import com.alibaba.druid.sql.visitor.SQLASTVisitor;
  * 
  * @author WENSHAO
  */
-public class SQLBitStringLiteralExpr extends SQLLiteralExpr {
+public class SQLBitStringLiteralExpr extends SQLExprImpl implements SQLLiteralExpr {
 
     private static final long serialVersionUID = 1L;
 

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

@@ -15,9 +15,10 @@
  */
 package com.alibaba.druid.sql.ast.expr;
 
+import com.alibaba.druid.sql.ast.SQLExprImpl;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
-public class SQLDateLiteralExpr extends SQLLiteralExpr {
+public class SQLDateLiteralExpr extends SQLExprImpl implements SQLLiteralExpr {
 
     private static final long   serialVersionUID = 1L;
 

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

@@ -1,8 +1,9 @@
 package com.alibaba.druid.sql.ast.expr;
 
+import com.alibaba.druid.sql.ast.SQLExprImpl;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
-public class SQLDefaultExpr extends SQLLiteralExpr {
+public class SQLDefaultExpr extends SQLExprImpl implements SQLLiteralExpr {
 
     private static final long serialVersionUID = 1L;
 

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

@@ -15,9 +15,11 @@
  */
 package com.alibaba.druid.sql.ast.expr;
 
+import com.alibaba.druid.sql.ast.SQLExprImpl;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
+import com.alibaba.druid.util.HexBin;
 
-public class SQLHexExpr extends SQLLiteralExpr {
+public class SQLHexExpr extends SQLExprImpl implements SQLLiteralExpr {
 
     private static final long serialVersionUID = 1L;
 
@@ -76,4 +78,8 @@ public class SQLHexExpr extends SQLLiteralExpr {
         }
         return true;
     }
+    
+    public byte[] toBytes() {
+        return HexBin.decode(this.hex);
+    }
 }

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

@@ -15,9 +15,10 @@
  */
 package com.alibaba.druid.sql.ast.expr;
 
+import com.alibaba.druid.sql.ast.SQLExprImpl;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
-public class SQLHexStringLiteralExpr extends SQLLiteralExpr {
+public class SQLHexStringLiteralExpr extends SQLExprImpl implements SQLLiteralExpr {
 
     private static final long serialVersionUID = 1L;
 

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

@@ -15,6 +15,7 @@
  */
 package com.alibaba.druid.sql.ast.expr;
 
+import com.alibaba.druid.sql.ast.SQLExprImpl;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
 /**
@@ -22,7 +23,7 @@ import com.alibaba.druid.sql.visitor.SQLASTVisitor;
  * 
  * @author WENSHAO
  */
-public class SQLIntervalLiteralExpr extends SQLLiteralExpr {
+public class SQLIntervalLiteralExpr extends SQLExprImpl implements SQLLiteralExpr {
 
     private static final long serialVersionUID = 1L;
 

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

@@ -15,14 +15,9 @@
  */
 package com.alibaba.druid.sql.ast.expr;
 
-import com.alibaba.druid.sql.ast.SQLExprImpl;
+import com.alibaba.druid.sql.ast.SQLExpr;
 
-public abstract class SQLLiteralExpr extends SQLExprImpl {
+public interface SQLLiteralExpr extends SQLExpr {
 
-    private static final long serialVersionUID = 1L;
-
-    public SQLLiteralExpr(){
-
-    }
 
 }

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

@@ -15,9 +15,10 @@
  */
 package com.alibaba.druid.sql.ast.expr;
 
+import com.alibaba.druid.sql.ast.SQLExprImpl;
 import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
-public class SQLNullExpr extends SQLLiteralExpr {
+public class SQLNullExpr extends SQLExprImpl implements SQLLiteralExpr {
 
     private static final long serialVersionUID = 1L;
 

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

@@ -15,7 +15,9 @@
  */
 package com.alibaba.druid.sql.ast.expr;
 
-public abstract class SQLNumericLiteralExpr extends SQLLiteralExpr {
+import com.alibaba.druid.sql.ast.SQLExprImpl;
+
+public abstract class SQLNumericLiteralExpr extends SQLExprImpl implements SQLLiteralExpr {
 
     private static final long serialVersionUID = 1L;
 

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

@@ -15,7 +15,9 @@
  */
 package com.alibaba.druid.sql.ast.expr;
 
-public abstract class SQLTextLiteralExpr extends SQLLiteralExpr {
+import com.alibaba.druid.sql.ast.SQLExprImpl;
+
+public abstract class SQLTextLiteralExpr extends SQLExprImpl implements SQLLiteralExpr {
 
     private static final long serialVersionUID = 1L;
 

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

@@ -24,10 +24,16 @@ public class SQLVariantRefExpr extends SQLExprImpl {
 
     private String            name;
 
-    public SQLVariantRefExpr(String name){
+    private boolean           global           = false;
 
+    public SQLVariantRefExpr(String name){
         this.name = name;
     }
+    
+    public SQLVariantRefExpr(String name, boolean global){
+        this.name = name;
+        this.global = global;
+    }
 
     public SQLVariantRefExpr(){
 
@@ -82,4 +88,12 @@ public class SQLVariantRefExpr extends SQLExprImpl {
         return true;
     }
 
+    public boolean isGlobal() {
+        return global;
+    }
+
+    public void setGlobal(boolean global) {
+        this.global = global;
+    }
+
 }