Rumah >pangkalan data >tutorial mysql >Oracle有条件地插入数据
方法一: declare iExists int; begin select count(*) into iExists from表 where 条件; if iExists=0 then insert into 表 ( ... ) values ( ... ); end if; end; 声明iExists变量,通过条件在表中找出有重复的数量,如果没有,就把数据插入表中 方法二:
方法一:
declare
iExists int;
begin
select count(*) into iExists from 表 where 条件;
if iExists=0 then
insert into 表 ( ... ) values ( ... );
end if;
end;
声明iExists变量,通过条件在表中找出有重复的数量,如果没有,就把数据插入表中
方法二:
merge into 目标表
using 源表 | (select 语句)
on ( 条件 )
when matched then update set 列=值
delete where ( 列=值 )
when not matched then insert ( 列... ) values ( 值... );
利用merge 方法,匹配的更新或删除,不匹配的插入数据
oracle不支持insert into ... not exists 方法
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MSSQLServer 方法:
if not exists(select * from 表 where 条件... ) insert into 表 ( 列 ... ) values ( 值 ... );
或者
declare @iExists int
select @iExists=COUNT(*) from 表 where 条件... ;
if @iExists=0
begin
insert into 表 ( 列 ...) values ( 值 ... );
end;
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注:插入的先后不同,会影响结果 (Oracle 与MSSQL不一样)
1、
merge into student
using (select * from dual)
on (student.stno=1 and (student.stname='aaaa' or student.stname is null))
when not matched then
insert (stno,stname,birth )
values (1,'aaaa',sysdate);
2、
merge into student
using (select * from dual)
on (student.stno=1 and (student.stname='' or student.stname is null))
when not matched then
insert (stno,stname,birth )
values (1,'',sysdate);