【计算机三级数据库技术】第6章高级数据查询--附思维导图

Better Bench 发布时间：2021-02-21 20:56:29 ，浏览量：2

1 一般数据查询
- 1.1 top
- 1.2 CASE
- 1.3 INTO
2 查询结构的并、交、差运算
- 2.1 UNION
- 2.2 INTERSECT
- 2.3 EXCEPT
3 相关子查询
6 其他形式的子查询
- 6.1 替代子查询
- 6.2 派生表
7 其他一些查询功能
- 7.1 开窗函数
- 7.2 公用表表达式

在这里插入图片描述

1 一般数据查询 1.1 top

格式

select top 3 Sname from Students

1.2 CASE

select Sname,Slevel =
CASE
	WHEN Sgrade>90 THEN '优秀'
	WHEN Sgrade


    
        
        
        
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	[2] session_save_path(): open_basedir restriction in effect. File(/var/lib/php/session) is not within the allowed path(s): (/www/wwwroot/www.chaojiit.com/:/tmp/) /www/wwwroot/www.chaojiit.com/ThinkPHP/Common/functions.php 第 1239 行.
[8192] Array and string offset access syntax with curly braces is deprecated /www/wwwroot/www.chaojiit.com/ThinkPHP/Library/Think/Cache/Driver/File.class.php 第 59 行.
[8] Undefined variable: user /www/wwwroot/www.chaojiit.com/Application/Runtime/Cache/Home/3c8a1a47a3534a7b1252c226abfc3928.php 第 34 行.
[8] Undefined variable: user /www/wwwroot/www.chaojiit.com/Application/Runtime/Cache/Home/3c8a1a47a3534a7b1252c226abfc3928.php 第 134 行.
[8] Trying to access array offset on value of type null /www/wwwroot/www.chaojiit.com/Application/Runtime/Cache/Home/3c8a1a47a3534a7b1252c226abfc3928.php 第 134 行.
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【计算机三级数据库技术】第6章 高级数据查询--附思维导图

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【计算机三级数据库技术】第6章高级数据查询--附思维导图