From a0b6b62ba05a0c3b6791e014db38a21bf1969267 Mon Sep 17 00:00:00 2001
From: Lunny Xiao <xiaolunwen@gmail.com>
Date: Fri, 14 Apr 2017 10:49:02 +0800
Subject: [PATCH] fix #570

---
 session_sum_test.go | 28 ++++++++++++++++++++++++++++
 statement.go        |  8 ++++++--
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/session_sum_test.go b/session_sum_test.go
index 59e0f3cd..31a65f98 100644
--- a/session_sum_test.go
+++ b/session_sum_test.go
@@ -71,3 +71,31 @@ func TestSum(t *testing.T) {
 	assert.EqualValues(t, 1, len(sumsInt))
 	assert.EqualValues(t, i, int(sumsInt[0]))
 }
+
+func TestSumCustomColumn(t *testing.T) {
+	assert.NoError(t, prepareEngine())
+
+	type SumStruct struct {
+		Int   int
+		Float float32
+	}
+
+	var (
+		cases = []SumStruct{
+			{1, 6.2},
+			{2, 5.3},
+			{92, -0.2},
+		}
+	)
+
+	assert.NoError(t, testEngine.Sync2(new(SumStruct)))
+
+	cnt, err := testEngine.Insert(cases)
+	assert.NoError(t, err)
+	assert.EqualValues(t, 3, cnt)
+
+	sumInt, err := testEngine.Sum(new(SumStruct),
+		"CASE WHEN `int` <= 2 THEN `int` ELSE 0 END")
+	assert.NoError(t, err)
+	assert.EqualValues(t, 3, int(sumInt))
+}
diff --git a/statement.go b/statement.go
index d411f739..e3640b53 100644
--- a/statement.go
+++ b/statement.go
@@ -1188,12 +1188,16 @@ func (statement *Statement) genSumSQL(bean interface{}, columns ...string) (stri
 
 	var sumStrs = make([]string, 0, len(columns))
 	for _, colName := range columns {
-		sumStrs = append(sumStrs, fmt.Sprintf("COALESCE(sum(%s),0)", statement.Engine.Quote(colName)))
+		if !strings.Contains(colName, " ") && strings.Contains(colName, "(") {
+			colName = statement.Engine.Quote(colName)
+		}
+		sumStrs = append(sumStrs, fmt.Sprintf("COALESCE(sum(%s),0)", colName))
 	}
+	sumSelect := strings.Join(sumStrs, ", ")
 
 	condSQL, condArgs, _ := statement.genConds(bean)
 
-	return statement.genSelectSQL(strings.Join(sumStrs, ", "), condSQL), append(statement.joinArgs, condArgs...)
+	return statement.genSelectSQL(sumSelect, condSQL), append(statement.joinArgs, condArgs...)
 }
 
 func (statement *Statement) genSelectSQL(columnStr, condSQL string) (a string) {