| 数据检索 | 2.2 检索单个列 | SELECT prod_name FROM Products; | SQL语句不区分大小写 |
| 2.3 检索多个列 | SELECT prod_name，prod_id，prod_price FROM Products; | ||
| 2.4 检索所有列 | SELECT * FROM Products; | ||
| 2.5 检索不同的值 | SELECT DISTINCT vend_id FROM Products; | ||
| 2.6 限制结果 | SELECT TOP 5 prod_name FROM Products;(SQL server、Access) SELECT prod_name FROM Products FETCH FIRST 5 ROWS ONLY;（DB2） SELECT prod_name FROM Products WHERE ROWNUM <=5;(Oracle) SELECT prod_name FROM Products LIMIT 5;(MySQL、SQLite等) SELECT prod_name FROM Products LIMIT 4 OFFSET 3;(LIMIT 3,4) |
从第3行起的4行数据 | |
| 2.7 使用注释 | SELECT prod_name --这是一条注释（--之后的是注释） FROM Products; # 这是一条注释 （单行注释） /*这是一条注释，很长 （跨行注释，通常用于代码注释） 很长的注释*/ |
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| 排序检索数据 | 3.1 排序数据 | SELECT prod_name FROM Products ORDER BY prod_name; | 字母升序拍；可以通过非检索列进行排序 |
| 3.2 按多个列排序 | SELECT prod_name，prod_id，prod_price FROM Products ORDER BY prod_price，prod_name; |
prod_price相同时才按照prod_name | |
| 3.3 按列位置排序 | SELECT prod_name，prod_id，prod_price FROM Products ORDER BY 2,3; |
表示先按prod_id，再按prod_price排序 | |
| 3.4 指定排序方向 | SELECT prod_name，prod_id，prod_price FROM Products ORDER BY prod_price DESC; |
降序排列，大小写字母在排序时是否区分取决于数据库的配置 | |
| SELECT prod_name，prod_id，prod_price FROM Products ORDER BY prod_price DESC,prod_name; |
prod_name仍为升序，ASC表升序（默认） | ||
| 过滤数据 | 4.1 使用WHERR | SELECT prod_name，prod_price FROM Products WHERE prod_price = 3.49; |
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| SELECT prod_name，prod_price FROM Products WHERE prod_price = 3.49 ORDER BY prod_name; |
WHERE和ORDER BY组合用法 | ||
| 4.2 WHERE子句操作符 | =,<>,!=,<,<=,!<,>,>=,!>,BETWEEN,IS NULL | ||
| 4.2.2 不匹配检查 | SELECT vend_id，prod_name FROM Products WHERE vend_id<>‘DLL01‘; |
不匹配检查,字符串需要加引号<>与!=等价 | |
| 4.2.3 范围值检查 | SELECT prod_name，prod_price FROM Products WHERE prod_price BETWEEN 5 AND 10 |
包括5和10 | |
| 4.2.4 空值检查 | SELECT prod_name，prod_price FROM Products WHERE prod_price IS NULL; |
NULL与非匹配：空值不会被返回 | |
| 高级数据过滤 | 5.1.1 AND操作符 | SELECT prod_id，prod_price，prod_name FROM Products WHERE vend_id = ‘DLL01‘ AND prod_price<=4; |
可用多个AND，增加过滤条件 |
| 5.1.2 OR操作符 | SELECT prod_id，prod_price，prod_name FROM Products WHERE vend_id = ‘DLL01‘ OR vend_id = ‘BRS01‘; |
第一个条件满足时，不管第二个条件是否满足，相应行都被检索出来 | |
| SELECT prod_id，prod_price，prod_name FROM Products WHERE (vend_id = ‘DLL01‘ OR vend_id = ‘BRS01‘)AND prod_price<=10; |
组合使用，使用圆括号。AND优先级较高 | ||
| 5.2 IN操作符 | SELECT prod_name，prod_price FROM Products WHERE vend_id = IN（ ‘DLL01‘,‘BRS01‘) ORDER BY prod_name; |
功能与OR相当 | |
| SELECT prod_name，prod_price FROM Products WHERE vend_id = ‘DLL01‘OR vend_id = ‘BRS01‘ ORDER BY prod_name; |
改写IN语句 | ||
| 5.3 NOT操作符 | SELECT prod_name FROM Products WHERE NOT vend_id = ‘DLL01‘ ORDER BY prod_name; |
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| SELECT prod_name FROM Products WHERE vend_id <> ‘DLL01‘ ORDER BY prod_name; |
改写NOT语句 | ||
| 用通配符进行过滤 | 6.1.1 %通配符 | SELECT prod_id,prod_name FROM Products WHERE prod_name LIKE ‘Fish%‘; |
找出以Fish起头的词，Fish之后可以是0个字符；Acess需要使用*非%；大小写是否区分取决于数据库配置 |
| SELECT prod_id,prod_name FROM Products WHERE prod_name LIKE ‘%bean bag%‘; |
匹配任何包含bean bag的值 | ||
| SELECT prod_name FROM Products WHERE prod_name LIKE ‘F%y‘; |
匹配F开头，y结尾的值（b%@forta.com） %匹配0个、1个、多个字符 如果字符末尾是空格，则需要用F%y%来匹配 |
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| WHERE prod_name LIKE ‘%‘; | 不配匹配prod_name为NULL的行 | ||
| 6.1.2 _通配符 | SELECT prod_id,prod_name FROM Products WHERE prod_name LIKE ‘__ inch teddy bear‘; |
DB2不支持，Access用?非_ _只匹配单个字符，功能与%通，如需匹配2个字符，则需要使用__ |
原文：http://www.cnblogs.com/hotpsy/p/6917071.html