如何生成id为每个插入时递增的列

Question

这是我的表格,我希望我的PNRNo为第一个条目生成'PNRRES001',连续条目为'PNRRES002','PNRRES002'等等.因此,在创建表时,我只调用该列来生成PNR否,用户只需从前端输入CustomerNo,PNR和Customer No的数据将更新为PNRDetails表.

CREATE TABLE PNRDetails(PNRNo AS (DBO.FuncIncPNR()) ,customerNo INT

--FUNCTION TO GENERATE THE PNR NUMBER
ALTER FUNCTION dbo.FuncIncPNR()
RETURNS VARCHAR(20)
AS 
BEGIN
DECLARE @RR VARCHAR(20) SET @RR='PNRRESA001'
--here i have checked if no value is there then return the first value as 'PNRRESA001'
    IF((SELECT COUNT(*)FROM PNRDetails)=0)
    BEGIN
    RETURN @RR
    END
    ELSE
-- if any value is there then take the last value and add 1 to it and update to the table
    BEGIN
    DECLARE @pnr VARCHAR(20),@S1 VARCHAR(20),@S2 INT
    DECLARE PNRCursor CURSOR Static
    FOR SELECT PNRNo FROM PNRDetails
    OPEN PNRCursor
    FETCH LAST FROM PNRNo INTO @pnr
    SET @S1=SUBSTRING(@pnr,1,7)
    SET @S2=RIGHT(@PNR,3)
    SET @S2=@S2+1;
    SET @pnr=@S1+@S2;

    END
    RETURN @pnr
END

--Here am inserting only customerNo as 5 and the PNR should be generated by my function
INSERT INTO PNRDetails VALUES(5)
--it shows 1 row updated  :)
SELECT * FROM PNRDetails
-- but when i run select command it shows
--Maximum stored procedure, function, trigger, or view nesting level exceeded (limit 32).  :(

你可以运行这个.如果你找到任何可以帮助我的东西,请帮忙.任何帮助将不胜感激......等待您的回复......

Answer 1

您可以尝试使用计算列和标识列.

create table PNRDetails
(
  ID int identity,
  PNRNo as 'PNRRES'+right(1000+ID, 3),
  customerNo int
)

Answer 2

我建议只使用IDENTITY作为你的id,让SQL Server处理每个id号的分配及其所有内置的并发保护,并将格式保留到UI ....或者,创建一个计算列如果您确实需要在DB中使用它,则定义ID的格式化版本.

您使用预期方法运行的风险是:

• 表现不佳
• 并发问题 - 如果在同一时间生成大量的ID