improve output visitor

src/main/java/com/alibaba/druid/sql/dialect/sqlserver/visitor/SQLServerParameterizedOutputVisitor.java

@@ -22,6 +22,7 @@ import com.alibaba.druid.sql.ast.expr.SQLIntegerExpr;
 import com.alibaba.druid.sql.ast.expr.SQLNCharExpr;
 import com.alibaba.druid.sql.ast.expr.SQLNullExpr;
 import com.alibaba.druid.sql.ast.expr.SQLNumberExpr;
+import com.alibaba.druid.sql.ast.expr.SQLVariantRefExpr;
 import com.alibaba.druid.sql.visitor.ParameterizedOutputVisitorUtils;
 import com.alibaba.druid.sql.visitor.ParameterizedVisitor;
 
@@ -90,5 +91,13 @@ public class SQLServerParameterizedOutputVisitor extends SQLServerOutputVisitor
 
         return ParameterizedOutputVisitorUtils.visit(this, x);
     }
+    
+    public boolean visit(SQLVariantRefExpr x) {
+        if (!ParameterizedOutputVisitorUtils.checkParameterize(x) || x.getName().equalsIgnoreCase("?")) {
+            return super.visit(x);
+        }
+        
+        return ParameterizedOutputVisitorUtils.visit(this, x);
+    }
 
 }

src/main/java/com/alibaba/druid/sql/visitor/ParameterizedOutputVisitorUtils.java

@@ -189,6 +189,12 @@ public class ParameterizedOutputVisitorUtils {
         v.incrementReplaceCunt();
         return false;
     }
+    
+    public static boolean visit(ParameterizedVisitor v, SQLVariantRefExpr x) {
+        v.print('?');
+        v.incrementReplaceCunt();
+        return false;
+    }
 
     public static SQLBinaryOpExpr merge(ParameterizedVisitor v, SQLBinaryOpExpr x) {
         SQLExpr left = x.getLeft();

src/main/java/com/alibaba/druid/sql/visitor/SQLASTOutputVisitor.java

@@ -601,7 +601,9 @@ public class SQLASTOutputVisitor extends SQLASTVisitorAdapter implements Printab
             decrementIndent();
         } else if (parent instanceof ValuesClause) {
             println();
+            print("(");
             x.getSubQuery().accept(this);
+            print(")");
             println();
         } else {
             print("(");