Add test for limit with query (#1787)

Reviewed-on: https://gitea.com/xorm/xorm/pulls/1787
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-committed-by: Lunny Xiao <xiaolunwen@gmail.com>

integrations/session_query_test.go

@@ -396,3 +396,25 @@ func TestJoinWithSubQuery(t *testing.T) {
 	assert.EqualValues(t, 1, len(querys))
 	assert.EqualValues(t, q, querys[0])
 }
+
+func TestQueryStringWithLimit(t *testing.T) {
+	assert.NoError(t, PrepareEngine())
+
+	if testEngine.Dialect().URI().DBType == schemas.MSSQL {
+		t.SkipNow()
+		return
+	}
+
+	type QueryWithLimit struct {
+		Id       int64  `xorm:"autoincr pk"`
+		Msg      string `xorm:"varchar(255)"`
+		DepartId int64
+		Money    float32
+	}
+
+	assert.NoError(t, testEngine.Sync2(new(QueryWithLimit)))
+
+	data, err := testEngine.Table("query_with_limit").Limit(20, 20).QueryString()
+	assert.NoError(t, err)
+	assert.EqualValues(t, 0, len(data))
+}

internal/statements/query.go

@@ -247,6 +247,9 @@ func (statement *Statement) genSelectSQL(columnStr string, needLimit, needOrderB
 			top = fmt.Sprintf("TOP %d ", LimitNValue)
 		}
 		if statement.Start > 0 {
+			if statement.RefTable == nil {
+				return "", nil, errors.New("Unsupported query limit without reference table")
+			}
 			var column string
 			if len(statement.RefTable.PKColumns()) == 0 {
 				for _, index := range statement.RefTable.Indexes {