Posts Categorized: SQLSERVER

sql server 2008 sa账户无法登录，错误：233

Posted by & filed under SQLSERVER.

http://hi.baidu.com/cive/blog/item/bd4e8e82a714d0b26c81198d.html

重新安装了sql server 2008，发现sa账户无法登录，错误是233。

网上找了很多帖子，

设置了“SQL   Server和Windows身份验证模式”，

也设置了sa“启用”，

也重启了N次，

都不行，

偶然看到一个办法，一试就好了。

如下：

 

用Windows身份验证登录，执行SQL命令：

ALTER LOGIN sa WITH PASSWORD=’新密码’，

搞定，现在终于可以用sa登录SQL管理器了。

…

Recursive Relationships

Posted by & filed under DATABASE, ORACLE, SQLSERVER.

Recursive relationships: relationships exist between entity instances of the same type.

One-to-one: If we were to track which employees were married to other employees, we would expect each to be married to either zero or one other employee at any …

多对多必须通过单独的一张表来表示

Posted by & filed under DATABASE, ORACLE, SQLSERVER.

如班级和教师的关系由三张表来表示：班级表，教师 及 班级教师表

In particular, the logical model does not contain any many-to-many relationships. There is a simple rationale for this difference – relational databases do not directly support many-to-many relationships, so they must be transformed using an intersection entity.…

About Count

Posted by & filed under ORACLE, SQLSERVER.

select count(*) FROM [AdventureWorks].[Person].[Contact]
返回表中所有的记录的个数

select COUNT(MiddleName) from [AdventureWorks].[Person].[Contact]
返回字段中，值非空的记录的个数（重复的也算进去的） 

select COUNT(distinct MiddleName) from [AdventureWorks].[Person].[Contact]
返回字段中不重复且非空的记录的个数

Result:
19972
11473
70…

Cursors in SQL

Posted by & filed under DATABASE, ORACLE, SQLSERVER.

SQL was designed as a set-oriented processing language. Some business rules( or poor physical design) require performing actions on row-by-row basis. Consider the following example:
. Increase the price of books <=$15 by 15%
. Decrease the price of books …