improve sql parser

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

@@ -0,0 +1,42 @@
+package com.alibaba.druid.sql.ast.statement;
+
+import com.alibaba.druid.sql.ast.SQLExpr;
+import com.alibaba.druid.sql.ast.SQLHint;
+import com.alibaba.druid.sql.ast.SQLObjectImpl;
+import com.alibaba.druid.sql.visitor.SQLASTVisitor;
+
+
+@SuppressWarnings("serial")
+public class SQLExprHint extends SQLObjectImpl implements SQLHint {
+    private SQLExpr expr;
+    
+    public SQLExprHint() {
+        
+    }
+    
+    public SQLExprHint(SQLExpr expr) {
+        this.setExpr(expr);
+    }
+
+    public SQLExpr getExpr() {
+        return expr;
+    }
+    
+    public void setExpr(SQLExpr expr) {
+        if (expr != null) {
+            expr.setParent(this);
+        }
+        
+        this.expr = expr;
+    }
+
+    @Override
+    protected void accept0(SQLASTVisitor visitor) {
+        if (visitor.visit(this)) {
+            acceptChild(visitor, expr);
+        }
+        visitor.endVisit(this);
+    }
+    
+    
+}