表tab有一字段a,不是自增字段,数据构成为:2009040001,前六位为日期年月,后4位为编号
插入数据时,先通过年月查找是否有该年月的编号,有则增加1,例如2009040002,没有则创建新的编号例如2009050001,请问如何避免多用户同时插入时值重复问题
数据库为sql server 2005
插入数据时,先通过年月查找是否有该年月的编号,有则增加1,例如2009040002,没有则创建新的编号例如2009050001,请问如何避免多用户同时插入时值重复问题
数据库为sql server 2005
我想写成这样不知道可不可以(伪代码)
事务{
lock(表)
查询编号,并计算插入编号
插入数据
unlock(表)
}在sqlserver2005不知道锁表怎么锁呢
下面代码是获取INT型,你需要前后截取字符串,然后比较.
--如果想进行断号处理
--以下三段,存储过程一样,只是显示不同数据时的情况.
--这是没有数据时.
create table tb(id int)
gocreate proc my_proc @id int OUTPUT
as
begin
if not exists (select 1 from tb)
set @id = 1
else
begin
select @id = min(m.px) + 1 from
(select * , px = (select count(1) from tb where id < t.id) + 1 from tb t) m,
(select * , px = (select count(1) from tb where id < t.id) + 1 from tb t) n
where m.id <> n.id - 1 and m.px = n.px - 1
if @id is null
select @id = max(id) + 1 from tb
end
end
godeclare @id as intexec my_proc @id outputselect @iddrop table tb
drop proc my_proc/*
-----------
1(所影响的行数为 1 行)
*/--这是存在断号时.create table tb(id int)
insert into tb values(1)
insert into tb values(3)gocreate proc my_proc @id int OUTPUT
as
begin
if not exists (select 1 from tb)
set @id = 1
else
begin
select @id = min(m.px) + 1 from
(select * , px = (select count(1) from tb where id < t.id) + 1 from tb t) m,
(select * , px = (select count(1) from tb where id < t.id) + 1 from tb t) n
where m.id <> n.id - 1 and m.px = n.px - 1
if @id is null
select @id = max(id) + 1 from tb
end
end
godeclare @id as intexec my_proc @id outputselect @iddrop table tb
drop proc my_proc/*
-----------
2
(所影响的行数为 1 行)
*/--这是不存在断号时.
create table tb(id int)
insert into tb values(1)
insert into tb values(2)gocreate proc my_proc @id int OUTPUT
as
begin
if not exists (select 1 from tb)
set @id = 1
else
begin
select @id = min(m.px) + 1 from
(select * , px = (select count(1) from tb where id < t.id) + 1 from tb t) m,
(select * , px = (select count(1) from tb where id < t.id) + 1 from tb t) n
where m.id <> n.id - 1 and m.px = n.px - 1
if @id is null
select @id = max(id) + 1 from tb
end
end
godeclare @id as intexec my_proc @id outputselect @iddrop table tb
drop proc my_proc/*
-----------
3
(所影响的行数为 1 行)
*/
--以下代码生成的编号长度为12,前6位为日期信息,格式为YYMMDD,后6位为流水号。
--创建得到当前日期的视图
CREATE VIEW v_GetDate
AS
SELECT dt=CONVERT(CHAR(6),GETDATE(),12)
GO--得到新编号的函数
CREATE FUNCTION f_NextBH()
RETURNS char(12)
AS
BEGIN
DECLARE @dt CHAR(6)
SELECT @dt=dt FROM v_GetDate
RETURN(
SELECT @dt+RIGHT(1000001+ISNULL(RIGHT(MAX(BH),6),0),6)
FROM tb WITH(XLOCK,PAGLOCK)
WHERE BH like @dt+'%')
END
GO--在表中应用函数
CREATE TABLE tb(
BH char(12) PRIMARY KEY DEFAULT dbo.f_NextBH(),
col int)--插入资料
INSERT tb(col) VALUES(1)
INSERT tb(col) VALUES(2)
INSERT tb(col) VALUES(3)
DELETE tb WHERE col=3
INSERT tb(col) VALUES(4)
INSERT tb(BH,col) VALUES(dbo.f_NextBH(),14)--显示结果
SELECT * FROM tb
/*--结果
BH col
------------------- -----------
050405000001 1
050405000002 2
050405000003 4
050405000004 14
--*/