From bae684b3639dff3e35d0ed330bc82c12e8282110 Mon Sep 17 00:00:00 2001
From: weih <weih.cao@gmail.com>
Date: Thu, 10 Aug 2023 13:34:33 +0800
Subject: [PATCH] fix(clause): when the value of clause.Eq is an empty array,
 the SQL should be IN (NULL) (#6503)

---
 clause/expression.go      | 16 ++++++++++------
 clause/expression_test.go |  5 +++++
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/clause/expression.go b/clause/expression.go
index 92ac7f22..8d010522 100644
--- a/clause/expression.go
+++ b/clause/expression.go
@@ -246,15 +246,19 @@ func (eq Eq) Build(builder Builder) {
 
 	switch eq.Value.(type) {
 	case []string, []int, []int32, []int64, []uint, []uint32, []uint64, []interface{}:
-		builder.WriteString(" IN (")
 		rv := reflect.ValueOf(eq.Value)
-		for i := 0; i < rv.Len(); i++ {
-			if i > 0 {
-				builder.WriteByte(',')
+		if rv.Len() == 0 {
+			builder.WriteString(" IN (NULL)")
+		} else {
+			builder.WriteString(" IN (")
+			for i := 0; i < rv.Len(); i++ {
+				if i > 0 {
+					builder.WriteByte(',')
+				}
+				builder.AddVar(builder, rv.Index(i).Interface())
 			}
-			builder.AddVar(builder, rv.Index(i).Interface())
+			builder.WriteByte(')')
 		}
-		builder.WriteByte(')')
 	default:
 		if eqNil(eq.Value) {
 			builder.WriteString(" IS NULL")
diff --git a/clause/expression_test.go b/clause/expression_test.go
index aaede61c..b997bf11 100644
--- a/clause/expression_test.go
+++ b/clause/expression_test.go
@@ -199,6 +199,11 @@ func TestExpression(t *testing.T) {
 		},
 		ExpectedVars: []interface{}{"a", "b"},
 		Result:       "`column-name` NOT IN (?,?)",
+	}, {
+		Expressions: []clause.Expression{
+			clause.Eq{Column: column, Value: []string{}},
+		},
+		Result: "`column-name` IN (NULL)",
 	}, {
 		Expressions: []clause.Expression{
 			clause.Eq{Column: clause.Expr{SQL: "SUM(?)", Vars: []interface{}{clause.Column{Name: "id"}}}, Value: 100},