Merge pull request #350 from pingcap/sheni/issue-320

*: SubSelect can be used as select statement

parser/parser.y

@@ -3481,6 +3481,12 @@ Statement:
 |	UnionStmt
 |	UpdateStmt
 |	UseStmt
+|	SubSelect
+	{
+		// `(select 1)`; is a valid select statement
+		// TODO: This is used to fix issue #320. There may be a better solution.
+		$$ = $1.(*subquery.SubQuery).Stmt
+	}
 
 ExplainableStmt:
 	SelectStmt

parser/parser_test.go

@@ -282,6 +282,9 @@ func (s *testParserSuite) TestDMLStmt(c *C) {
 		// For show create table
 		{"show create table test.t", true},
 		{"show create table t", true},
+
+		// For https://github.com/pingcap/tidb/issues/320
+		{`(select 1);`, true},
 	}
 	s.RunTest(c, table)
 }

tidb.go

@@ -257,7 +257,8 @@ func trimSQL(sql string) string {
 		}
 		break
 	}
-	return sql
+	// Trim leading '('. For `(select 1);` is also a query.
+	return strings.TrimLeft(sql, "( ")
 }
 
 // IsQuery checks if a sql statement is a query statement.

tidb_test.go

@@ -300,6 +300,7 @@ func (s *testMainSuite) TestIsQuery(c *C) {
 		{"/*comment*/ select 1;", true},
 		{"/*comment*/ /*comment*/ select 1;", true},
 		{"select /*comment*/ 1 /*comment*/;", true},
+		{"(select /*comment*/ 1 /*comment*/);", true},
 	}
 	for _, t := range tbl {
 		c.Assert(IsQuery(t.sql), Equals, t.ok, Commentf(t.sql))