利用數據庫觸發器讓字段與自增長Id相關聯
阿新 • • 發佈:2018-04-27
過程 過多 調用 trigge ase cas varchar color http
十年河東,十年河西,莫欺少年窮
學無止境,精益求精
今天是數據庫腳本類的代碼,所以不想過多闡述
如下數據表:
create table Card( Id int identity(1,1) primary key, CardNo varchar(50) unique not null, Status bit default(0) )
上述表中有自增長字段Id,現在要求字段 CardNo 和自增長Id 相關聯,譬如,當Id為1時,CardNo 應該為 Card00001,當Id為15時,CardNo應該為: Card00015 ,要求通過觸發器或存儲過程實現?
其中觸發器實現如下:
create TRIGGER[dbo].[TGR_Card] ON [dbo].[Card] AFTER INSERT AS BEGIN -- SET NOCOUNT ON added to prevent extra result sets from -- interfering with SELECT statements. SET NOCOUNT ON; -- Insert statements for trigger here、 DECLARE @Id bigint SELECT @Id = Id FROM INSERTEDUPDATE Card SET CardNo = CASE WHEN LEN(@Id) = 1 THEN ‘Crad0000000‘ + CAST(@Id AS varchar(20)) WHEN LEN(@Id) = 2 THEN ‘Crad000000‘ + CAST(@Id AS varchar(20)) WHEN LEN(@Id) = 3 THEN‘Crad00000‘ + CAST(@Id AS varchar(20)) WHEN LEN(@Id) = 4 THEN ‘Crad0000‘ + CAST(@Id AS varchar(20)) WHEN LEN(@Id) = 5 THEN ‘Crad000‘ + CAST(@Id AS varchar(20)) WHEN LEN(@Id) = 6 THEN ‘Crad00‘ + CAST(@Id AS varchar(20)) WHEN LEN(@Id) = 7 THEN ‘Crad0‘ + CAST(@Id AS varchar(20)) WHEN LEN(@Id) = 8 THEN ‘Crad‘ + CAST(@Id AS varchar(20)) END WHERE orderId = @Id END
如果用存儲過程如何實現呢?
存儲過程實現就需要考慮如下因素了:
1、存儲過程需要程序調用執行
2、如果同一時刻多條數據插入數據庫時,就應該考慮到數據並發,因此,采用存儲過程實現應該避免並發
那麽,存儲過程應該怎麽實現呢?
我們都知道,防止並發我們采用樂觀鎖或悲觀鎖,在此不做演示了,總之,要加上版本字段 ,數據庫類型:TimeStamp!
關於並發的避免大家可參考:http://www.cnblogs.com/chenwolong/p/Lock.html
http://www.cnblogs.com/chenwolong/p/BF.html
@陳臥龍的博客
利用數據庫觸發器讓字段與自增長Id相關聯