add Exists func

builder/crud.go

@@ -364,7 +364,7 @@ func (ex *Builder) Delete() (int64, error) {
 	return ex.ExecAffected(sqlStr, paramList...)
 }
 
-// Truncate 清空记录, sqlte3不支持此操作
+// Truncate 清空记录, sqlite3不支持此操作
 func (ex *Builder) Truncate() (int64, error) {
 	sqlStr := "TRUNCATE TABLE " + ex.tableName
 	if ex.driverName == model.Sqlite3 {
@@ -374,6 +374,27 @@ func (ex *Builder) Truncate() (int64, error) {
 	return ex.ExecAffected(sqlStr)
 }
 
+// Exists 存在某记录
+func (ex *Builder) Exists() (bool, error) {
+	var obj IntStruct
+	err := ex.Select("1 as c").Limit(0, 1).GetOne(&obj)
+	if err != nil {
+		return false, err
+	}
+
+	if obj.C.Int64 == 1 {
+		return true, nil
+	} else {
+		return false, nil
+	}
+}
+
+// DoesntExist 不存在某记录
+func (ex *Builder) DoesntExist() (bool, error) {
+	isE, err := ex.Exists()
+	return !isE, err
+}
+
 // Value 字段值
 func (ex *Builder) Value(fieldName string, dest interface{}) error {
 	ex.Select(fieldName).Limit(0, 1)

test/aorm_test.go

@@ -79,7 +79,16 @@ func TestAll(t *testing.T) {
 		testGetOne(dbItem.DriverName, dbItem.DbLink, id)
 		testGetMany(dbItem.DriverName, dbItem.DbLink)
 		testUpdate(dbItem.DriverName, dbItem.DbLink, id)
+		isExists := testExists(dbItem.DriverName, dbItem.DbLink, id)
+		if isExists != true {
+			panic("应该存在，但是数据库不存在")
+		}
+
 		testDelete(dbItem.DriverName, dbItem.DbLink, id)
+		isExists2 := testExists(dbItem.DriverName, dbItem.DbLink, id)
+		if isExists2 == true {
+			panic("应该不存在，但是数据库存在")
+		}
 
 		id2 := testInsert(dbItem.DriverName, dbItem.DbLink)
 		testTable(dbItem.DriverName, dbItem.DbLink)
@@ -301,6 +310,14 @@ func testDelete(driver string, db *sql.DB, id int64) {
 	}
 }
 
+func testExists(driver string, db *sql.DB, id int64) bool {
+	exists, err := aorm.Use(db).Driver(driver).Debug(false).Where(&Person{Id: null.IntFrom(id)}).OrderBy("id", "DESC").Exists()
+	if err != nil {
+		panic(driver + " testExists " + "found err:" + err.Error())
+	}
+	return exists
+}
+
 func testTable(driver string, db *sql.DB) {
 	_, err := aorm.Use(db).Debug(false).Driver(driver).Table("person_1").Insert(&Person{Name: null.StringFrom("Cherry")})
 	if err != nil {