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如何進(jìn)行DB2和SQLServer自增列比較

如何進(jìn)行DB2 和SQL Server自增列比較，相信很多沒有經(jīng)驗(yàn)的人對(duì)此束手無策，為此本文總結(jié)了問題出現(xiàn)的原因和解決方法，通過這篇文章希望你能解決這個(gè)問題。

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最近由于對(duì)SQL Server的自增列理解不夠好，導(dǎo)致了一個(gè)設(shè)計(jì)問題，做了2個(gè)小例子解釋一下

SQL Server的自增列
create table identitytest(
      id int identity(1,1),
      name varchar(20)
)
go
set IDENTITY_INSERT identitytest ON
go
insert into identitytest(id,name)values(1,'test1')
go
insert into identitytest(id,name)values(2,'test2')
go
set IDENTITY_INSERT identitytest OFF
go
insert into identitytest(name)values('test3')
go
set IDENTITY_INSERT identitytest ON
go
insert into identitytest(id,name)values(10000,'test4')
go
set IDENTITY_INSERT identitytest OFF
go
insert into identitytest(name)values('test5')

go
id      name
1       test1
2       test2
3       test3
10000   test4
10001   test5
(5 rows affected)
1>

SQL Server的自增列的值取決于表里面的此列的當(dāng)前的最大值。 create table identitytest(
id bigint not null generated by default as identity (start with 1,increment by 1),
name varchar(20)
);
insert into identitytest(id,name)values(1,'test1');
insert into identitytest(id,name)values(2,'test2');
insert into identitytest(name)values('test3');
insert into identitytest(id,name)values(10000,'test4');
insert into identitytest(name)values('test5');

db2 => select * from identitytest;

ID                   NAME
-------------------- --------------------
                   1 test1
                   2 test2
                   1 test3
               10000 test4
                   2 test5

5 record(s) selected.

db2 =>

DB2的自增列，當(dāng)你手工插入自增列的值的時(shí)候，DB2會(huì)無視你插入的值，DB2用自增列的定義產(chǎn)生值。