Subtract is conflict with Subtract(e1,e2)

Subtract is conflict with Subtract(e1,e2)  in this file so i change the name except
in basic operator i rename it  Subtract

Author: YanjieGao

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SqlParser.scala

@@ -119,7 +119,7 @@ class SqlParser extends StandardTokenParsers with PackratParsers {
   protected val UNCACHE = Keyword("UNCACHE")
   protected val UNION = Keyword("UNION")
   protected val WHERE = Keyword("WHERE")
-  protected val SUBTRACT = Keyword("EXCEPT")
+  protected val EXCEPT = Keyword("EXCEPT")
 
   // Use reflection to find the reserved words defined in this class.
   protected val reservedWords =
@@ -137,14 +137,12 @@ class SqlParser extends StandardTokenParsers with PackratParsers {
     }
   }
 
-  protected lazy val query: Parser[LogicalPlan] = (
-    select * (
-        UNION ~ ALL ^^^ { (q1: LogicalPlan, q2: LogicalPlan) => Union(q1, q2) } |
-        UNION ~ opt(DISTINCT) ^^^ { (q1: LogicalPlan, q2: LogicalPlan) => Distinct(Union(q1, q2)) } |
-        SUBTRACT  ^^^ { (q1: LogicalPlan, q2: LogicalPlan) => Subtract(q1, q2) } 
-      )
-    | insert | cache
-  )
+  protected lazy val query: Parser[LogicalPlan] =
+   select * (
+           UNION ~ ALL ^^^ { (q1: LogicalPlan, q2: LogicalPlan) => Union(q1, q2)} |
+           UNION ~ opt(DISTINCT) ^^^ { (q1: LogicalPlan, q2: LogicalPlan) => Distinct(Union(q1, q2))} |
+           EXCEPT ^^^ { (q1: LogicalPlan, q2: LogicalPlan) => Except(q1, q2)}
+   ) | insert
 
   protected lazy val select: Parser[LogicalPlan] =
     SELECT ~> opt(DISTINCT) ~ projections ~