sql server中in和exists的小区别 oracle未测试
in 的话， 如果是null 就不比较了，既不是in 也不是 not in
exists的话 因为用 = 加在条件里比较了，所以 null 是 not exists
select *
from pricetemp
where cast(商品コード as varchar(10))not in(
select shohin_cd
from m_price)
select *
from pricetemp
where not exists (select shohin_cd
from m_price
where cast(pricetemp.商品コード as varchar(10))=m_price.shohin_cd)
以上2条会有不同的结果，因为 pricetemp.商品コード 有很多 null
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GRANT
Name
GRANT -- 定义访问权限
Synopsis GRANT { { SELECT | INSERT | UPDATE | DELETE | RULE | REFERENCES | TRIGGER }
[,...] | ALL [ PRIVILEGES ] }
ON [ TABLE ] tablename [, ...]
TO { username | GROUP groupname | PUBLIC } [, ...] [ WI ......
PairWise subquery:
e.g.:
select * from wf_docsort where (ndocsortid,nmoduleinfoid) in (select ndocsortid, nmoduleinfoid from wf_docsort where instr(cname,'文')>0)
the above sql is the same function as:
select * from wf_docsort where ndocsortid = (select ndocsortid from wf_docsort where ......
1. My test: (create and grant the sysdba to a new user by SQL*Plus)
CREATE USER FJTEST1 IDENTIFIED BY JEANJEANFANG;
GRANT SYSDBA TO FJTEST;
REVOKE SYSDBA from FJTEST;
CONNECT FJTEST1/JEANJEANFANG AS SYSDBA;
2. Using ORAPWD in windows:
C:\» ORAPWD;
(show help information)
3. to see th ......
using System;
using System.Collections;
using System.Collections.Specialized;
using System.Collections.Generic;
using System.Text;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Runtime.InteropServices;
using System.Windows.Forms;
namespace DAL
{
......
以前一直觉得linq to sql生成类似where id not in (1,3,5)或where id not in (select id from ...)这样的条件不是很方便，每次我都是把条件ID事先取到一个数组里，然后用 !Arr.Contains(c.Id)这样处理，今天突然发现这样好傻，其实可以完全直接用linq写成一句，贴个示例在这里，以后备查
from a in TableA where !(fr ......
