fix(clause): when the value of clause.Eq is an empty array, the SQL s…

…hould be IN (NULL) (#6503)

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")

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},