exp, err := ParseSelectStatement("select _3,_1,_2 as 'mytest'  from S3object")
	if err != nil {
		t.Fatalf("parse alias sql error: %v", err)
	}
	if exp.selectAST.Expression.Expressions[2].As != "mytest" {
		t.Fatalf("parse alias sql error: %s not equal %s", exp.selectAST.Expression.Expressions[2].As, err)
	}