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最新文章列表
Some projects cannot be imported because they already exist in the workspace err
Q:
I am trying to import a project that me and my co-worker have been working on.. and keep getting this error after I select-- "import" then "import existing project" then click a ...
oracle中的exists 和not exists 用法详解
有两个简单例子,以说明 “exists”和“in”的效率问题
1) select * from T1 where exists(select 1 from T2 where T1.a=T2.a) ;
T1数据量小而T2数据量非常大时,T1<<T2 时,1) 的查询效率高。
2) select * from T1 where T1.a in (select T2.a fr ...
解决在eclipse中导入项目名称已存在的问题
设置Eclipse智能提示 转自
http://blog.csdn.net/sz_bdqn/article/details/4956162
1、Some projects cannot be imported because they already exist in the workspace
2、Some projects were hidden because they exist i ...
sql中exist与in 的区别
以下内容借鉴过来的!
今天在网上查资料看sql中exist与in 的区别,发现众说纷纭,有几种说法:
1. exist效率比in高,凡是in都应该用exist替换
2. 外大内小用in,外小内大用exist
3. 外大内小用exist,外小内大用in
一时分辨不了哪个正确,于是动手检验.
数据库: ORACLE 10G
客户端: PlSqlDev 7.1
1. 外大 ...