6.1、基本查询语句
MySQL从数据表中查询数据的基本语句为SELECT语句，其基本格式为：
SELECT
{* | <字段列表>}
[
FROM <表1>,<表2>...
[WHERE 表达式
[GROUP BY <group by deFinition>]
[HAVING <expression> [{<operator> <expression>}...]]
[ORDER BY <order by deFinition>]
[LIMIT [<offset>,] <row count> ]
]
]
SELECT [字段1,字段2,...,字段n]
FROM [表或视图]
WHERE [查询条件]
各条子句的含义：
|
{* | <字段列表>}：包含星号通配符选择字段列表，表示查询的字段，其字段列至少包含一个字段名称。 FROM <表1>,<表2>...：表1，表2表示查询数据的来源 GROUP BY <字段>：告诉MysqL如何显示查询出来的数据，并按照指定字段分组 |
MysqL> CREATE TABLE fruits -> ( -> f_id char(10) NOT NULL, -> s_id INT NOT NULL, -> f_name char(255) NOT NULL, -> f_price decimal(8,2) NOT NULL, -> PRIMARY KEY(f_id) -> ); Query OK, 0 rows affected (0.05 sec) MysqL> INSERT INTO fruits (f_id, s_id, f_name, f_price) -> VALUES('a1', 101,'apple',5.2), -> ('b1',101,'blackBerry', 10.2), -> ('bs1',102,'orange', 11.2), -> ('bs2',105,'melon',8.2), -> ('t1',102,'banana', 10.3), -> ('t2',102,'grape', 5.3), -> ('o2',103,'coconut', 9.2), -> ('c0',101,'cherry', 3.2), -> ('a2',103, 'apricot',2.2), -> ('l2',104,'lemon', 6.4), -> ('b2',104,'Berry', 7.6), -> ('m1',106,'mango', 15.6), -> ('m2',105,'xbabay', 2.6), -> ('t4',107,'xbababa', 3.6), -> ('m3',105,'xxtt', 11.6), -> ('b5',107,'xxxx', 3.6); Query OK, 16 rows affected (0.09 sec) Records: 16 Duplicates: 0 Warnings: 0
6.2、单表查询
查询所有字段
语法： SELECT * FROM 表名
MysqL> SELECT * FROM fruits; +------+------+------------+---------+ | f_id | s_id | f_name | f_price | +------+------+------------+---------+ | a1 | 101 | apple | 5.20 | | a2 | 103 | apricot | 2.20 | | b1 | 101 | blackBerry | 10.20 | | b2 | 104 | Berry | 7.60 | | b5 | 107 | xxxx | 3.60 | | bs1 | 102 | orange | 11.20 | | bs2 | 105 | melon | 8.20 | | c0 | 101 | cherry | 3.20 | | l2 | 104 | lemon | 6.40 | | m1 | 106 | mango | 15.60 | | m2 | 105 | xbabay | 2.60 | | m3 | 105 | xxtt | 11.60 | | o2 | 103 | coconut | 9.20 | | t1 | 102 | banana | 10.30 | | t2 | 102 | grape | 5.30 | | t4 | 107 | xbababa | 3.60 | +------+------+------------+---------+ 16 rows in set (0.00 sec)
查询指定字段
语法： SELECT 字段名1,字段名2,... FROM 表名
MysqL> SELECT f_name FROM fruits; +------------+ | f_name | +------------+ | apple | | apricot | | blackBerry | | Berry | | xxxx | | orange | | melon | | cherry | | lemon | | mango | | xbabay | | xxtt | | coconut | | banana | | grape | | xbababa | +------------+ 16 rows in set (0.00 sec) MysqL> SELECT f_name,f_price FROM fruits; +------------+---------+ | f_name | f_price | +------------+---------+ | apple | 5.20 | | apricot | 2.20 | | blackBerry | 10.20 | | Berry | 7.60 | | xxxx | 3.60 | | orange | 11.20 | | melon | 8.20 | | cherry | 3.20 | | lemon | 6.40 | | mango | 15.60 | | xbabay | 2.60 | | xxtt | 11.60 | | coconut | 9.20 | | banana | 10.30 | | grape | 5.30 | | xbababa | 3.60 | +------------+---------+ 16 rows in set (0.00 sec)
查询指定记录
语法： SELECT 字段名1,字段名2,... FROM 表名 WHERE 查询条件
WHERE条件判断符
| 操作符 | 说明 |
| = | 相等 |
| <>,!= | 不等于 |
| < |
小于 |
| <= |
小于等于 |
| > |
大于 |
| >= |
大于等于 |
| BETWEEN | 位于两值之间 |
MysqL> SELECT f_name, f_price -> FROM fruits -> WHERE f_price = 10.2; +------------+---------+ | f_name | f_price | +------------+---------+ | blackBerry | 10.20 | +------------+---------+ 1 row in set (0.00 sec) MysqL> SELECT f_name, f_price -> FROM fruits -> WHERE f_name = 'apple'; +--------+---------+ | f_name | f_price | +--------+---------+ | apple | 5.20 | +--------+---------+ 1 row in set (0.00 sec) MysqL> SELECT f_name, f_price -> FROM fruits -> WHERE f_price < 10; +---------+---------+ | f_name | f_price | +---------+---------+ | apple | 5.20 | | apricot | 2.20 | | Berry | 7.60 | | xxxx | 3.60 | | melon | 8.20 | | cherry | 3.20 | | lemon | 6.40 | | xbabay | 2.60 | | coconut | 9.20 | | grape | 5.30 | | xbababa | 3.60 | +---------+---------+ 11 rows in set (0.00 sec)
带IN关键字的查询
IN操作符用来查询满足指定范围内的条件记录，使用IN操作符，将所有检索条件用括号括起来，检索条件之间用逗号分隔开，只要满足条件范围内的一个值即可。
MysqL> SELECT s_id,f_name, f_price -> FROM fruits -> WHERE s_id IN (101,102) -> ORDER BY f_name; +------+------------+---------+ | s_id | f_name | f_price | +------+------------+---------+ | 101 | apple | 5.20 | | 102 | banana | 10.30 | | 101 | blackBerry | 10.20 | | 101 | cherry | 3.20 | | 102 | grape | 5.30 | | 102 | orange | 11.20 | +------+------------+---------+ 6 rows in set (0.00 sec) MysqL> SELECT s_id,f_name, f_price -> FROM fruits -> WHERE s_id NOT IN (101,102) -> ORDER BY f_name; +------+---------+---------+ | s_id | f_name | f_price | +------+---------+---------+ | 103 | apricot | 2.20 | | 104 | Berry | 7.60 | | 103 | coconut | 9.20 | | 104 | lemon | 6.40 | | 106 | mango | 15.60 | | 105 | melon | 8.20 | | 107 | xbababa | 3.60 | | 105 | xbabay | 2.60 | | 105 | xxtt | 11.60 | | 107 | xxxx | 3.60 | +------+---------+---------+ 10 rows in set (0.00 sec)
带BETWEEN AND的范围查询
BETWEEN AND用来查询某个范围内的值，该操作符需要两个参数，即范围的开始和结束，如果字段满足指定的范围查询条件，则这些记录被返回。
MysqL> SELECT f_name, f_price -> FROM fruits -> WHERE f_price BETWEEN 2.00 AND 10.20; +------------+---------+ | f_name | f_price | +------------+---------+ | apple | 5.20 | | apricot | 2.20 | | blackBerry | 10.20 | | Berry | 7.60 | | xxxx | 3.60 | | melon | 8.20 | | cherry | 3.20 | | lemon | 6.40 | | xbabay | 2.60 | | coconut | 9.20 | | grape | 5.30 | | xbababa | 3.60 | +------------+---------+ 12 rows in set (0.00 sec) MysqL> SELECT f_name, f_price -> FROM fruits -> WHERE f_price NOT BETWEEN 2.00 AND 10.20; +--------+---------+ | f_name | f_price | +--------+---------+ | orange | 11.20 | | mango | 15.60 | | xxtt | 11.60 | | banana | 10.30 | +--------+---------+ 4 rows in set (0.00 sec)
带LIKE的字符匹配查询
%通配符，匹配任意长度任意字符
MysqL> SELECT f_id, f_name -> FROM fruits -> WHERE f_name LIKE 'b%'; +------+------------+ | f_id | f_name | +------+------------+ | b1 | blackBerry | | b2 | Berry | | t1 | banana | +------+------------+ 3 rows in set (0.00 sec) MysqL> SELECT f_id, f_name -> FROM fruits -> WHERE f_name LIKE '%g%'; +------+--------+ | f_id | f_name | +------+--------+ | bs1 | orange | | m1 | mango | | t2 | grape | +------+--------+ 3 rows in set (0.00 sec)
_通配符：匹配单个字符
MysqL> SELECT f_id, f_name FROM fruits WHERE f_name LIKE '____e'; +------+--------+ | f_id | f_name | +------+--------+ | a1 | apple | | t2 | grape | +------+--------+ 2 rows in set (0.00 sec)
查询空值
数据表创建的时候，可以指定某列中可以包含空值（NULL），空值不同于0，也不同于空字符串。空值一般表示数据未知、不适用或将在以后添加数据。使用IS NULL子句可以查询某字段内容为空的记录。
MysqL> CREATE TABLE customers -> ( -> c_id int NOT NULL AUTO_INCREMENT, -> c_name char(50) NOT NULL, -> c_address char(50) NULL, -> c_city char(50) NULL, -> c_zip char(10) NULL, -> c_contact char(50) NULL, -> c_email char(255) NULL, -> PRIMARY KEY (c_id) -> ); Query OK, 0 rows affected (0.02 sec) MysqL> INSERT INTO customers(c_id, c_name, c_address, c_city, -> c_zip, c_contact, c_email) -> VALUES(10001, 'RedHook', '200 Street ', 'Tianjin', -> '300000', 'LiMing', 'LMing@163.com'), -> (10002, 'Stars', '333 Fromage Lane', -> 'dalian', '116000', 'Zhangbo','Jerry@hotmail.com'), -> (10003, 'Netbhood', '1 Sunny Place', 'Qingdao', '266000', -> 'LuoCong', NULL), -> (10004, 'JOTO', '829 Riverside Drive', 'Haikou', -> '570000', 'YangShan', 'sam@hotmail.com'); Query OK, 4 rows affected (0.02 sec) Records: 4 Duplicates: 0 Warnings: 0 MysqL> SELECT c_id, c_name,c_email FROM customers WHERE c_email IS NULL; +-------+----------+---------+ | c_id | c_name | c_email | +-------+----------+---------+ | 10003 | Netbhood | NULL | +-------+----------+---------+ 1 row in set (0.00 sec) MysqL> SELECT c_id, c_name,c_email FROM customers WHERE c_email IS NOT NULL; +-------+---------+-------------------+ | c_id | c_name | c_email | +-------+---------+-------------------+ | 10001 | RedHook | LMing@163.com | | 10002 | Stars | Jerry@hotmail.com | | 10004 | JOTO | sam@hotmail.com | +-------+---------+-------------------+ 3 rows in set (0.00 sec)
带AND的多条件查询
MysqL> SELECT f_id, f_price, f_name FROM fruits WHERE s_id = '101' AND f_price >=5; +------+---------+------------+ | f_id | f_price | f_name | +------+---------+------------+ | a1 | 5.20 | apple | | b1 | 10.20 | blackBerry | +------+---------+------------+ 2 rows in set (0.00 sec) MysqL> SELECT f_id, f_price, f_name FROM fruits -> WHERE s_id IN('101', '102') AND f_price >= 5 AND f_name = 'apple'; +------+---------+--------+ | f_id | f_price | f_name | +------+---------+--------+ | a1 | 5.20 | apple | +------+---------+--------+ 1 row in set (0.00 sec)
带OR的多条件查询
MysqL> SELECT s_id,f_name, f_price -> FROM fruits -> WHERE s_id = 101 OR s_id = 102; +------+------------+---------+ | s_id | f_name | f_price | +------+------------+---------+ | 101 | apple | 5.20 | | 101 | blackBerry | 10.20 | | 102 | orange | 11.20 | | 101 | cherry | 3.20 | | 102 | banana | 10.30 | | 102 | grape | 5.30 | +------+------------+---------+ 6 rows in set (0.00 sec) MysqL> SELECT s_id,f_name, f_price -> FROM fruits -> WHERE s_id IN(101,102); +------+------------+---------+ | s_id | f_name | f_price | +------+------------+---------+ | 101 | apple | 5.20 | | 101 | blackBerry | 10.20 | | 102 | orange | 11.20 | | 101 | cherry | 3.20 | | 102 | banana | 10.30 | | 102 | grape | 5.30 | +------+------------+---------+ 6 rows in set (0.00 sec)
OR操作符和IN操作符使用后结果一样，可以实现相同的功能。但是使用IN操作符使检索语句更加简明，并且IN执行的速度更快于OR。
查询结果不重复
MysqL中使用disTINCT关键字消除重复的记录，其语法为：
SELECT disTINCT 字段名 FROM 表名
MysqL> SELECT s_id FROM fruits; +------+ | s_id | +------+ | 101 | | 103 | | 101 | | 104 | | 107 | | 102 | | 105 | | 101 | | 104 | | 106 | | 105 | | 105 | | 103 | | 102 | | 102 | | 107 | +------+ 16 rows in set (0.00 sec) MysqL> SELECT disTINCT s_id FROM fruits; +------+ | s_id | +------+ | 101 | | 103 | | 104 | | 107 | | 102 | | 105 | | 106 | +------+ 7 rows in set (0.00 sec)
对查询的结果排序
单列排序
MysqL> SELECT f_name FROM fruits; +------------+ | f_name | +------------+ | apple | | apricot | | blackBerry | | Berry | | xxxx | | orange | | melon | | cherry | | lemon | | mango | | xbabay | | xxtt | | coconut | | banana | | grape | | xbababa | +------------+ 16 rows in set (0.00 sec) MysqL> SELECT f_name FROM fruits ORDER BY f_name; +------------+ | f_name | +------------+ | apple | | apricot | | banana | | Berry | | blackBerry | | cherry | | coconut | | grape | | lemon | | mango | | melon | | orange | | xbababa | | xbabay | | xxtt | | xxxx | +------------+ 16 rows in set (0.00 sec)
多列排序
MysqL> SELECT f_name, f_price FROM fruits ORDER BY f_name, f_price; +------------+---------+ | f_name | f_price | +------------+---------+ | apple | 5.20 | | apricot | 2.20 | | banana | 10.30 | | Berry | 7.60 | | blackBerry | 10.20 | | cherry | 3.20 | | coconut | 9.20 | | grape | 5.30 | | lemon | 6.40 | | mango | 15.60 | | melon | 8.20 | | orange | 11.20 | | xbababa | 3.60 | | xbabay | 2.60 | | xxtt | 11.60 | | xxxx | 3.60 | +------------+---------+ 16 rows in set (0.00 sec)
指定方向排序
MysqL> SELECT f_name, f_price FROM fruits ORDER BY f_price DESC; +------------+---------+ | f_name | f_price | +------------+---------+ | mango | 15.60 | | xxtt | 11.60 | | orange | 11.20 | | banana | 10.30 | | blackBerry | 10.20 | | coconut | 9.20 | | melon | 8.20 | | Berry | 7.60 | | lemon | 6.40 | | grape | 5.30 | | apple | 5.20 | | xxxx | 3.60 | | xbababa | 3.60 | | cherry | 3.20 | | xbabay | 2.60 | | apricot | 2.20 | +------------+---------+ 16 rows in set (0.00 sec) MysqL> SELECT f_price, f_name FROM fruits ORDER BY f_price DESC, f_name; +---------+------------+ | f_price | f_name | +---------+------------+ | 15.60 | mango | | 11.60 | xxtt | | 11.20 | orange | | 10.30 | banana | | 10.20 | blackBerry | | 9.20 | coconut | | 8.20 | melon | | 7.60 | Berry | | 6.40 | lemon | | 5.30 | grape | | 5.20 | apple | | 3.60 | xbababa | | 3.60 | xxxx | | 3.20 | cherry | | 2.60 | xbabay | | 2.20 | apricot | +---------+------------+ 16 rows in set (0.00 sec)
分组查询
分组查询是对数据按照某个或多个字段进行分组，MysqL中使用GROUP BY 关键字对数据进行分组，基本语法形式为：
[GROUP BY 字段] [HAVING <条件表达式>]
创建分组
GROUP BY关键字通常和集合函数一起使用，如MAX()、MIN()、COUNT()、SUM()、AVG()。
MysqL> SELECT s_id, COUNT(*) AS Total FROM fruits GROUP BY s_id; +------+-------+ | s_id | Total | +------+-------+ | 101 | 3 | | 102 | 3 | | 103 | 2 | | 104 | 2 | | 105 | 3 | | 106 | 1 | | 107 | 2 | +------+-------+ 7 rows in set (0.00 sec) MysqL> SELECT s_id, GROUP_CONCAT(f_name) AS Names FROM fruits GROUP BY s_id; +------+-------------------------+ | s_id | Names | +------+-------------------------+ | 101 | apple,blackBerry,cherry | | 102 | grape,banana,orange | | 103 | apricot,coconut | | 104 | lemon,Berry | | 105 | xbabay,xxtt,melon | | 106 | mango | | 107 | xxxx,xbababa | +------+-------------------------+ 7 rows in set (0.00 sec)
使用HAVING过滤分组
MysqL> SELECT s_id, GROUP_CONCAT(f_name) AS Names -> FROM fruits -> GROUP BY s_id HAVING COUNT(f_name) > 1; +------+-------------------------+ | s_id | Names | +------+-------------------------+ | 101 | apple,blackBerry,cherry | | 102 | grape,banana,orange | | 103 | apricot,coconut | | 104 | lemon,Berry | | 105 | xbabay,xxtt,melon | | 107 | xxxx,xbababa | +------+-------------------------+ 6 rows in set (0.00 sec)
在GROUP BY 子句中使用WITH ROLLUP，显示查询出的所有记录总和
MysqL> SELECT s_id, COUNT(*) AS Total -> FROM fruits -> GROUP BY s_id WITH ROLLUP; +------+-------+ | s_id | Total | +------+-------+ | 101 | 3 | | 102 | 3 | | 103 | 2 | | 104 | 2 | | 105 | 3 | | 106 | 1 | | 107 | 2 | | NULL | 16 | +------+-------+ 8 rows in set (0.00 sec)
多字段分组
MysqL> SELECT * FROM fruits group by s_id,f_name; +------+------+------------+---------+ | f_id | s_id | f_name | f_price | +------+------+------------+---------+ | a1 | 101 | apple | 5.20 | | b1 | 101 | blackBerry | 10.20 | | c0 | 101 | cherry | 3.20 | | t1 | 102 | banana | 10.30 | | t2 | 102 | grape | 5.30 | | bs1 | 102 | orange | 11.20 | | a2 | 103 | apricot | 2.20 | | o2 | 103 | coconut | 9.20 | | b2 | 104 | Berry | 7.60 | | l2 | 104 | lemon | 6.40 | | bs2 | 105 | melon | 8.20 | | m2 | 105 | xbabay | 2.60 | | m3 | 105 | xxtt | 11.60 | | m1 | 106 | mango | 15.60 | | t4 | 107 | xbababa | 3.60 | | b5 | 107 | xxxx | 3.60 | +------+------+------------+---------+ 16 rows in set (0.00 sec)
GROUP BY 和ORDER BY一起使用
MysqL> CREATE TABLE orderitems -> ( -> o_num int NOT NULL, -> o_item int NOT NULL, -> f_id char(10) NOT NULL, -> quantity int NOT NULL, -> item_price decimal(8,2) NOT NULL, -> PRIMARY KEY (o_num,o_item) -> ) ; Query OK, 0 rows affected (0.09 sec) MysqL> INSERT INTO orderitems(o_num, o_item, f_id, quantity, item_price) -> VALUES(30001, 1, 'a1', 10, 5.2), -> (30001, 2, 'b2', 3, 7.6), -> (30001, 3, 'bs1', 5, 11.2), -> (30001, 4, 'bs2', 15, 9.2), -> (30002, 1, 'b3', 2, 20.0), -> (30003, 1, 'c0', 100, 10), -> (30004, 1, 'o2', 50, 2.50), -> (30005, 1, 'c0', 5, 10), -> (30005, 2, 'b1', 10, 8.99), -> (30005, 3, 'a2', 10, 2.2), -> (30005, 4, 'm1', 5, 14.99); Query OK, 11 rows affected (0.08 sec) Records: 11 Duplicates: 0 Warnings: 0 MysqL> SELECT o_num, SUM(quantity * item_price) AS orderTotal -> FROM orderitems -> GROUP BY o_num -> HAVING SUM(quantity*item_price) >= 100; +-------+------------+ | o_num | orderTotal | +-------+------------+ | 30001 | 268.80 | | 30003 | 1000.00 | | 30004 | 125.00 | | 30005 | 236.85 | +-------+------------+ 4 rows in set (0.00 sec) MysqL> SELECT o_num, SUM(quantity * item_price) AS orderTotal -> FROM orderitems -> GROUP BY o_num -> HAVING SUM(quantity*item_price) >= 100 -> ORDER BY orderTotal; +-------+------------+ | o_num | orderTotal | +-------+------------+ | 30004 | 125.00 | | 30005 | 236.85 | | 30001 | 268.80 | | 30003 | 1000.00 | +-------+------------+ 4 rows in set (0.00 sec)
LIMIT [位置偏移量,] 行数
MysqL> SELECT * From fruits LIMIT 4; +------+------+------------+---------+ | f_id | s_id | f_name | f_price | +------+------+------------+---------+ | a1 | 101 | apple | 5.20 | | a2 | 103 | apricot | 2.20 | | b1 | 101 | blackBerry | 10.20 | | b2 | 104 | Berry | 7.60 | +------+------+------------+---------+ 4 rows in set (0.00 sec) MysqL> SELECT * From fruits LIMIT 4, 3; +------+------+--------+---------+ | f_id | s_id | f_name | f_price | +------+------+--------+---------+ | b5 | 107 | xxxx | 3.60 | | bs1 | 102 | orange | 11.20 | | bs2 | 105 | melon | 8.20 | +------+------+--------+---------+ 3 rows in set (0.00 sec)
有时不需要返回实际表中的数据，而只是针对数据进行总结。MysqL提供一些查询功能，可以获取数据进行分析和报告。
| 函数 | 作用 |
| AVG() | 返回某列的平均值 |
| COUNT() | 返回某列的行数 |
| MAX() |
返回某列的最大值 |
| MIN() |
返回某列的最小值 |
| SUM() |
返回某列值的和 |
COUNT()函数
MysqL> SELECT COUNT(*) AS cust_num -> FROM customers; +----------+ | cust_num | +----------+ | 4 | +----------+ 1 row in set (0.00 sec) MysqL> SELECT COUNT(c_email) AS email_num -> FROM customers; +-----------+ | email_num | +-----------+ | 3 | +-----------+ 1 row in set (0.00 sec) MysqL> SELECT o_num, COUNT(f_id) -> FROM orderitems -> GROUP BY o_num; +-------+-------------+ | o_num | COUNT(f_id) | +-------+-------------+ | 30001 | 4 | | 30002 | 1 | | 30003 | 1 | | 30004 | 1 | | 30005 | 4 | +-------+-------------+ 5 rows in set (0.00 sec)
SUM()函数
MysqL> SELECT SUM(quantity) AS items_total -> FROM orderitems -> WHERE o_num = 30005; +-------------+ | items_total | +-------------+ | 30 | +-------------+ 1 row in set (0.00 sec) MysqL> SELECT o_num, SUM(quantity) AS items_total -> FROM orderitems -> GROUP BY o_num; +-------+-------------+ | o_num | items_total | +-------+-------------+ | 30001 | 33 | | 30002 | 2 | | 30003 | 100 | | 30004 | 50 | | 30005 | 30 | +-------+-------------+ 5 rows in set (0.00 sec)
AVG()函数
MysqL> SELECT AVG(f_price) AS avg_price -> FROM fruits -> WHERE s_id = 103; +-----------+ | avg_price | +-----------+ | 5.700000 | +-----------+ 1 row in set (0.00 sec) MysqL> SELECT s_id,AVG(f_price) AS avg_price -> FROM fruits -> GROUP BY s_id; +------+-----------+ | s_id | avg_price | +------+-----------+ | 101 | 6.200000 | | 102 | 8.933333 | | 103 | 5.700000 | | 104 | 7.000000 | | 105 | 7.466667 | | 106 | 15.600000 | | 107 | 3.600000 | +------+-----------+ 7 rows in set (0.00 sec)
MAX()函数
MysqL> SELECT MAX(f_price) AS max_price FROM fruits; +-----------+ | max_price | +-----------+ | 15.60 | +-----------+ 1 row in set (0.00 sec) MysqL> SELECT s_id, MAX(f_price) AS max_price -> FROM fruits -> GROUP BY s_id; +------+-----------+ | s_id | max_price | +------+-----------+ | 101 | 10.20 | | 102 | 11.20 | | 103 | 9.20 | | 104 | 7.60 | | 105 | 11.60 | | 106 | 15.60 | | 107 | 3.60 | +------+-----------+ 7 rows in set (0.00 sec) MysqL> SELECT MAX(f_name) FROM fruits; +-------------+ | MAX(f_name) | +-------------+ | xxxx | +-------------+ 1 row in set (0.00 sec)
MIN()函数
MysqL> SELECT MIN(f_price) AS min_price FROM fruits; +-----------+ | min_price | +-----------+ | 2.20 | +-----------+ 1 row in set (0.00 sec) MysqL> SELECT s_id, MIN(f_price) AS min_price -> FROM fruits -> GROUP BY s_id; +------+-----------+ | s_id | min_price | +------+-----------+ | 101 | 3.20 | | 102 | 5.30 | | 103 | 2.20 | | 104 | 6.40 | | 105 | 2.60 | | 106 | 15.60 | | 107 | 3.60 | +------+-----------+ 7 rows in set (0.00 sec)
6.4、连接查询
连接是关系数据库模型的主要特点。连接查询是关系数据库中最主要的查询。主要包括内连接、外连接等。通过连接元算符可以实现多个表查询。在关系数据库管理系统中，表建立时各个数据之间关系不确定，常把一个实体的所有信息存在一个表中。当查询时，通过连接操作查询出存在多个表中的不同实体的信息。
内连接查询
内连接使用比较运算符进行表间某些列数据的比较操作，并列出这些表中与连接条件相匹配的数据行，组合成新记录。
首先创建表与插入数据：
MysqL> CREATE TABLE suppliers -> ( -> s_id int NOT NULL AUTO_INCREMENT, -> s_name char(50) NOT NULL, -> s_city char(50) NULL, -> s_zip char(10) NULL, -> s_call CHAR(50) NOT NULL, -> PRIMARY KEY (s_id) -> ) ; Query OK, 0 rows affected (0.03 sec) MysqL> INSERT INTO suppliers(s_id, s_name,s_city, s_zip, s_call) -> VALUES(101,'FastFruit Inc.','Tianjin','300000','48075'), -> (102,'LT Supplies','Chongqing','400000','44333'), -> (103,'Acme','Shanghai','200000','90046'), -> (104,'FNK Inc.','Zhongshan','528437','11111'), -> (105,'Good Set','Taiyuang','030000', '22222'), -> (106,'Just Eat Ours','Beijing','010', '45678'), -> (107,'DK Inc.','Zhengzhou','450000', '33332'); Query OK, 7 rows affected (0.01 sec) Records: 7 Duplicates: 0 Warnings: 0
MysqL> SELECT suppliers.s_id, s_name,f_name, f_price -> FROM fruits ,suppliers -> WHERE fruits.s_id = suppliers.s_id; +------+----------------+------------+---------+ | s_id | s_name | f_name | f_price | +------+----------------+------------+---------+ | 101 | FastFruit Inc. | apple | 5.20 | | 103 | Acme | apricot | 2.20 | | 101 | FastFruit Inc. | blackBerry | 10.20 | | 104 | FNK Inc. | Berry | 7.60 | | 107 | DK Inc. | xxxx | 3.60 | | 102 | LT Supplies | orange | 11.20 | | 105 | Good Set | melon | 8.20 | | 101 | FastFruit Inc. | cherry | 3.20 | | 104 | FNK Inc. | lemon | 6.40 | | 106 | Just Eat Ours | mango | 15.60 | | 105 | Good Set | xbabay | 2.60 | | 105 | Good Set | xxtt | 11.60 | | 103 | Acme | coconut | 9.20 | | 102 | LT Supplies | banana | 10.30 | | 102 | LT Supplies | grape | 5.30 | | 107 | DK Inc. | xbababa | 3.60 | +------+----------------+------------+---------+ 16 rows in set (0.00 sec) MysqL> SELECT suppliers.s_id, s_name,f_name, f_price -> FROM fruits INNER JOIN suppliers -> ON fruits.s_id = suppliers.s_id; +------+----------------+------------+---------+ | s_id | s_name | f_name | f_price | +------+----------------+------------+---------+ | 101 | FastFruit Inc. | apple | 5.20 | | 103 | Acme | apricot | 2.20 | | 101 | FastFruit Inc. | blackBerry | 10.20 | | 104 | FNK Inc. | Berry | 7.60 | | 107 | DK Inc. | xxxx | 3.60 | | 102 | LT Supplies | orange | 11.20 | | 105 | Good Set | melon | 8.20 | | 101 | FastFruit Inc. | cherry | 3.20 | | 104 | FNK Inc. | lemon | 6.40 | | 106 | Just Eat Ours | mango | 15.60 | | 105 | Good Set | xbabay | 2.60 | | 105 | Good Set | xxtt | 11.60 | | 103 | Acme | coconut | 9.20 | | 102 | LT Supplies | banana | 10.30 | | 102 | LT Supplies | grape | 5.30 | | 107 | DK Inc. | xbababa | 3.60 | +------+----------------+------------+---------+ 16 rows in set (0.00 sec)
如果在一个连接查询中，设计的两个表是同一张表，这种查询称为字连接查询。例如：查询供应f_id= ‘a1’的水果供应商提供的其他水果种类。
MysqL> SELECT f1.f_id, f1.f_name -> FROM fruits AS f1, fruits AS f2 -> WHERE f1.s_id = f2.s_id AND f2.f_id = 'a1'; +------+------------+ | f_id | f_name | +------+------------+ | a1 | apple | | b1 | blackBerry | | c0 | cherry | +------+------------+ 3 rows in set (0.00 sec)
外间接查询
外连接查询将查询多个表中相关联的行，其分为左外连接和右外连接
左外连接：返回包括左表中的所有记录和右表中连接字段相等的记录
首先创建表和数据：
MysqL> CREATE TABLE orders -> ( -> o_num int NOT NULL AUTO_INCREMENT, -> o_date datetime NOT NULL, -> c_id int NOT NULL, -> PRIMARY KEY (o_num) -> ) ; Query OK, 0 rows affected (0.05 sec) MysqL> INSERT INTO orders(o_num, o_date, c_id) -> VALUES(30001, '2008-09-01', 10001), -> (30002, '2008-09-12', 10003), -> (30003, '2008-09-30', 10004), -> (30004, '2008-10-03', 10005), -> (30005, '2008-10-08', 10001); Query OK, 5 rows affected (0.02 sec) Records: 5 Duplicates: 0 Warnings: 0 #在customers表和orders表中，查询所有客户，包括没有订单的客户 MysqL> SELECT customers.c_id, orders.o_num -> FROM customers LEFT OUTER JOIN orders -> ON customers.c_id = orders.c_id; +-------+-------+ | c_id | o_num | +-------+-------+ | 10001 | 30001 | | 10001 | 30005 | | 10002 | NULL | | 10003 | 30002 | | 10004 | 30003 | +-------+-------+ 5 rows in set (0.00 sec)
右外连接：返回包括右表中的所有记录和左表中连接字段相等的记录
#在customers表和orders表中，查询所有订单，包括没有客户的订单 MysqL> SELECT customers.c_id, orders.o_num -> FROM customers RIGHT OUTER JOIN orders -> ON customers.c_id = orders.c_id; +-------+-------+ | c_id | o_num | +-------+-------+ | 10001 | 30001 | | 10003 | 30002 | | 10004 | 30003 | | NULL | 30004 | | 10001 | 30005 | +-------+-------+ 5 rows in set (0.00 sec)
复合条件连接查询
复合条件连接查询实在连接查询的过程中，通过添加过滤条件，限制查询的结果，使查询的结果更加准确。
在customers表和orders表中，使用INNER JOIN语法查询customers表中ID为10001的客户的订单信息 MysqL> SELECT customers.c_id, orders.o_num -> FROM customers INNER JOIN orders -> ON customers.c_id = orders.c_id AND customers.c_id = 10001; +-------+-------+ | c_id | o_num | +-------+-------+ | 10001 | 30001 | | 10001 | 30005 | +-------+-------+ 2 rows in set (0.00 sec) 在fruits表和suppliers表之间，使用INNER JOIN语法进行内连接查询，并对查询结果排序 MysqL> SELECT suppliers.s_id, s_name,f_name, f_price -> FROM fruits INNER JOIN suppliers -> ON fruits.s_id = suppliers.s_id -> ORDER BY fruits.s_id; +------+----------------+------------+---------+ | s_id | s_name | f_name | f_price | +------+----------------+------------+---------+ | 101 | FastFruit Inc. | apple | 5.20 | | 101 | FastFruit Inc. | blackBerry | 10.20 | | 101 | FastFruit Inc. | cherry | 3.20 | | 102 | LT Supplies | grape | 5.30 | | 102 | LT Supplies | banana | 10.30 | | 102 | LT Supplies | orange | 11.20 | | 103 | Acme | apricot | 2.20 | | 103 | Acme | coconut | 9.20 | | 104 | FNK Inc. | lemon | 6.40 | | 104 | FNK Inc. | Berry | 7.60 | | 105 | Good Set | xbabay | 2.60 | | 105 | Good Set | xxtt | 11.60 | | 105 | Good Set | melon | 8.20 | | 106 | Just Eat Ours | mango | 15.60 | | 107 | DK Inc. | xxxx | 3.60 | | 107 | DK Inc. | xbababa | 3.60 | +------+----------------+------------+---------+ 16 rows in set (0.00 sec)
6.5、子查询
带ANY、SOME关键字的子查询
ANY和SOME关键字是同义词，表示满足其中任一条件，它们允许创建一个表达式对子查询的返回值列表进行比较，只要满足内层子查询中的任何一个比较条件，就返回一个结果作为外层查询的条件。
首先创建两张表，插入数据：
MysqL> CREATE table tbl1 ( num1 INT NOT NULL); Query OK, 0 rows affected (0.02 sec) MysqL> CREATE table tbl2 ( num2 INT NOT NULL); Query OK, 0 rows affected (0.03 sec) MysqL> INSERT INTO tbl1 values(1), (5), (13), (27); Query OK, 4 rows affected (0.02 sec) Records: 4 Duplicates: 0 Warnings: 0 MysqL> INSERT INTO tbl2 values(6), (14), (11), (20); Query OK, 4 rows affected (0.05 sec) Records: 4 Duplicates: 0 Warnings: 0 返回tbl2表的所有num2列，然后将tbl1中的num1的值与之进行比较，只要大于num2的任何1个值， 即为符合查询条件的结果。 MysqL> SELECT num1 FROM tbl1 WHERE num1 > ANY (SELECT num2 FROM tbl2); +------+ | num1 | +------+ | 13 | | 27 | +------+ 2 rows in set (0.00 sec)
带ALL关键字的子查询
ALL关键字与ANY不同，使用ALL时需要同时满足所有内层查询的条件。
返回tbl1表中比tbl2表num2 列所有值都大的值，sql语句如下： MysqL> SELECT num1 FROM tbl1 WHERE num1 > ALL (SELECT num2 FROM tbl2); +------+ | num1 | +------+ | 27 | +------+ 1 row in set (0.00 sec)
带EXISTS关键字的子查询
EXISTS关键字后面的参数是一个任意的子查询，系统对子查询进行运算以判断它是否返回行，如果至少返回一行，那么EXISTS的结果为TRUE，此时外层查询语句将进行查询。
查询suppliers表中是否存在s_id=107的供应商，如果存在，则查询fruits表中的记录 MysqL> SELECT * FROM fruits -> WHERE EXISTS -> (SELECT s_name FROM suppliers WHERE s_id = 107); +------+------+------------+---------+ | f_id | s_id | f_name | f_price | +------+------+------------+---------+ | a1 | 101 | apple | 5.20 | | a2 | 103 | apricot | 2.20 | | b1 | 101 | blackBerry | 10.20 | | b2 | 104 | Berry | 7.60 | | b5 | 107 | xxxx | 3.60 | | bs1 | 102 | orange | 11.20 | | bs2 | 105 | melon | 8.20 | | c0 | 101 | cherry | 3.20 | | l2 | 104 | lemon | 6.40 | | m1 | 106 | mango | 15.60 | | m2 | 105 | xbabay | 2.60 | | m3 | 105 | xxtt | 11.60 | | o2 | 103 | coconut | 9.20 | | t1 | 102 | banana | 10.30 | | t2 | 102 | grape | 5.30 | | t4 | 107 | xbababa | 3.60 | +------+------+------------+---------+ 16 rows in set (0.00 sec) 查询suppliers表中是否存在s_id=107的供应商，如果存在，则查询fruits表中的f_price大于10.20 的记录 MysqL> SELECT * FROM fruits -> WHERE f_price>10.20 AND EXISTS -> (SELECT s_name FROM suppliers WHERE s_id = 107); +------+------+--------+---------+ | f_id | s_id | f_name | f_price | +------+------+--------+---------+ | bs1 | 102 | orange | 11.20 | | m1 | 106 | mango | 15.60 | | m3 | 105 | xxtt | 11.60 | | t1 | 102 | banana | 10.30 | +------+------+--------+---------+ 4 rows in set (0.00 sec) 查询suppliers表中是否存在s_id=107的供应商，如果不存在则查询fruits表中的记录 MysqL> SELECT * FROM fruits -> WHERE NOT EXISTS -> (SELECT s_name FROM suppliers WHERE s_id = 107); Empty set (0.00 sec)
带IN关键字的子查询
IN 关键字进行子查询时，内层查询语句仅仅返回一个数据列，这个数据列里的值将提供给外层查询语句进行比较。
在orderitems表中查询f_id为c0的订单号，并根据订单号查询具有订单号的客户c_id MysqL> SELECT c_id FROM orders WHERE o_num IN -> (SELECT o_num FROM orderitems WHERE f_id = 'c0'); +-------+ | c_id | +-------+ | 10004 | | 10001 | +-------+ 2 rows in set (0.00 sec)
带比较运算符的子查询
在suppliers表中查询s_city等于“Tianjin”的供应商s_id，然后在fruits表中查询所有该供应商提 供的水果的种类 MysqL> SELECT s_id, f_name FROM fruits -> WHERE s_id = -> (SELECT s1.s_id FROM suppliers AS s1 WHERE s1.s_city = 'Tianjin'); +------+------------+ | s_id | f_name | +------+------------+ | 101 | apple | | 101 | blackBerry | | 101 | cherry | +------+------------+ 3 rows in set (0.00 sec) 在suppliers表中查询s_city等于“Tianjin”的供应商s_id，然后在fruits表中查询所有非该供应 商提供的水果的种类 MysqL> SELECT s_id, f_name FROM fruits -> WHERE s_id <> -> (SELECT s1.s_id FROM suppliers AS s1 WHERE s1.s_city = 'Tianjin'); +------+---------+ | s_id | f_name | +------+---------+ | 103 | apricot | | 104 | Berry | | 107 | xxxx | | 102 | orange | | 105 | melon | | 104 | lemon | | 106 | mango | | 105 | xbabay | | 105 | xxtt | | 103 | coconut | | 102 | banana | | 102 | grape | | 107 | xbababa | +------+---------+ 13 rows in set (0.00 sec)
6.6、合并查询结果
利用UNION关键字，可以给出多条SELECT语句，并将它们的结果组成单个结果集。合并时，两个表对应列的列数和数据类型必须相同。使用ALL关键字可以不删除重复行也不对结果进行排序。其基本语法为：
SELECT column,... FROM table1 UNION [ALL] SELECT column,... FROM table2
查询所有价格小于9的水果的信息，查询s_id等于101和103所有的水果的信息，使用UNION连接查询结果 MysqL> SELECT s_id, f_name, f_price -> FROM fruits -> WHERE f_price < 9.0 -> UNION ALL -> SELECT s_id, f_name, f_price -> FROM fruits -> WHERE s_id IN(101,103); +------+------------+---------+ | s_id | f_name | f_price | +------+------------+---------+ | 101 | apple | 5.20 | | 103 | apricot | 2.20 | | 104 | Berry | 7.60 | | 107 | xxxx | 3.60 | | 105 | melon | 8.20 | | 101 | cherry | 3.20 | | 104 | lemon | 6.40 | | 105 | xbabay | 2.60 | | 102 | grape | 5.30 | | 107 | xbababa | 3.60 | | 101 | apple | 5.20 | | 103 | apricot | 2.20 | | 101 | blackBerry | 10.20 | | 101 | cherry | 3.20 | | 103 | coconut | 9.20 | +------+------------+---------+ 15 rows in set (0.00 sec) 查询所有价格小于9的水果的信息，查询s_id等于101和103的所有水果的信息，使用UNION ALL连接查询结果 MysqL> SELECT s_id, f_name, f_price -> FROM fruits -> WHERE f_price < 9.0 -> UNION ALL -> SELECT s_id, f_name, f_price -> FROM fruits -> WHERE s_id IN(101,103); +------+------------+---------+ | s_id | f_name | f_price | +------+------------+---------+ | 101 | apple | 5.20 | | 103 | apricot | 2.20 | | 104 | Berry | 7.60 | | 107 | xxxx | 3.60 | | 105 | melon | 8.20 | | 101 | cherry | 3.20 | | 104 | lemon | 6.40 | | 105 | xbabay | 2.60 | | 102 | grape | 5.30 | | 107 | xbababa | 3.60 | | 101 | apple | 5.20 | | 103 | apricot | 2.20 | | 101 | blackBerry | 10.20 | | 101 | cherry | 3.20 | | 103 | coconut | 9.20 | +------+------------+---------+ 15 rows in set (0.00 sec)
6.7、为表和字段取别名
为表取别名
当表名字很长或者执行一些特殊查询时，为了方便可以为表指定别名，其语法格式为：
表名 [AS] 表别名
为orders表取别名o，查询30001订单的下单日期 MysqL> SELECT * FROM orders AS o -> WHERE o.o_num = 30001; +-------+---------------------+-------+ | o_num | o_date | c_id | +-------+---------------------+-------+ | 30001 | 2008-09-01 00:00:00 | 10001 | +-------+---------------------+-------+ 1 row in set (0.00 sec) 为customers和orders表分别取别名，并进行连接查询 MysqL> SELECT c.c_id, o.o_num -> FROM customers AS c LEFT OUTER JOIN orders AS o -> ON c.c_id = o.c_id; +-------+-------+ | c_id | o_num | +-------+-------+ | 10001 | 30001 | | 10001 | 30005 | | 10002 | NULL | | 10003 | 30002 | | 10004 | 30003 | +-------+-------+ 5 rows in set (0.00 sec)
为字段取别名
为字段取别名的语法格式为：
列名 [AS] 列别名
查询fruits表，为f_name取别名fruit_name，f_price取别名fruit_price，为fruits表取别名f1， 查询表中f_price < 8的水果的名称 MysqL> SELECT f1.f_name AS fruit_name, f1.f_price AS fruit_price -> FROM fruits AS f1 -> WHERE f1.f_price < 8; +------------+-------------+ | fruit_name | fruit_price | +------------+-------------+ | apple | 5.20 | | apricot | 2.20 | | Berry | 7.60 | | xxxx | 3.60 | | cherry | 3.20 | | lemon | 6.40 | | xbabay | 2.60 | | grape | 5.30 | | xbababa | 3.60 | +------------+-------------+ 9 rows in set (0.00 sec) 查询suppliers表中字段s_name和s_city，使用CONCAT函数连接这两个字段值，并取列别名为suppliers_title MysqL> SELECT CONCAT(TRIM(s_name) , ' (', TRIM(s_city), ')') -> AS suppliers_title -> FROM suppliers -> ORDER BY s_name; +--------------------------+ | suppliers_title | +--------------------------+ | Acme (Shanghai) | | DK Inc. (Zhengzhou) | | FastFruit Inc. (Tianjin) | | FNK Inc. (Zhongshan) | | Good Set (Taiyuang) | | Just Eat Ours (Beijing) | | LT Supplies (Chongqing) | +--------------------------+ 7 rows in set (0.00 sec)
6.8、使用正则表达式查询
正则表达式通常被用来检索或替换那些符合某个模式的文本内容，根据指定的匹配模式匹配文中符合要求的特殊字符串。
| 选项 | 说明 | 例子 | 匹配值示例 |
| ^ | 匹配文本的开始字符串 | '^b' | book,big,bike |
| $ | 匹配文本的结束字符串 | 'st$' | test,persist |
| . | 匹配任何单个字符 | 'b.t' | bit,bat,but |
| * |
匹配零个或多个前面的字符 | 'f*n' | fn,ffn,fffn |
| + |
匹配前面的字符1次或多次 | 'ba+' | baa,baaaa |
| <字符串> |
匹配包含指定的字符串文本 | 'fa' | fan,afa,faad |
| [字符集合] |
匹配字符集合中任意一个字符 | '[xz]' | dizzy,zebra,x-sd |
| [^] |
匹配不在括号中的任何一个字符 | '[^abc]' | qwe,ret,ryrty |
| 字符串{n,} |
匹配前面的字符至少n次 | 'b{2,}' | bbb,bbbb,bbbbbbb |
| 字符串{n,m} |
匹配前面的字符串至少n次，至多m次 | 'b{2,4}' | bb,bbb,bbbb |
在fruits表中，查询f_name字段以字母’b’开头的记录 MysqL> SELECT * FROM fruits WHERE f_name REGEXP '^b'; +------+------+------------+---------+ | f_id | s_id | f_name | f_price | +------+------+------------+---------+ | b1 | 101 | blackBerry | 10.20 | | b2 | 104 | Berry | 7.60 | | t1 | 102 | banana | 10.30 | +------+------+------------+---------+ 3 rows in set (0.00 sec) 在fruits表中，查询f_name字段以“be”开头的记录 MysqL> SELECT * FROM fruits WHERE f_name REGEXP '^be'; +------+------+--------+---------+ | f_id | s_id | f_name | f_price | +------+------+--------+---------+ | b2 | 104 | Berry | 7.60 | +------+------+--------+---------+ 1 row in set (0.00 sec) 在fruits表中，查询f_name字段以字母’y’结尾的记录 MysqL> SELECT * FROM fruits WHERE f_name REGEXP 'y$'; +------+------+------------+---------+ | f_id | s_id | f_name | f_price | +------+------+------------+---------+ | b1 | 101 | blackBerry | 10.20 | | b2 | 104 | Berry | 7.60 | | c0 | 101 | cherry | 3.20 | | m2 | 105 | xbabay | 2.60 | +------+------+------------+---------+ 4 rows in set (0.00 sec) 在fruits表中，查询f_name字段以字符串“rry”结尾的记录 MysqL> SELECT * FROM fruits WHERE f_name REGEXP 'rry$'; +------+------+------------+---------+ | f_id | s_id | f_name | f_price | +------+------+------------+---------+ | b1 | 101 | blackBerry | 10.20 | | b2 | 104 | Berry | 7.60 | | c0 | 101 | cherry | 3.20 | +------+------+------------+---------+ 3 rows in set (0.00 sec) 在fruits表中，查询f_name字段值包含字母’a’与’g’且两个字母之间只有一个字母的记录 MysqL> SELECT * FROM fruits WHERE f_name REGEXP 'a.g'; +------+------+--------+---------+ | f_id | s_id | f_name | f_price | +------+------+--------+---------+ | bs1 | 102 | orange | 11.20 | | m1 | 106 | mango | 15.60 | +------+------+--------+---------+ 2 rows in set (0.00 sec) 在fruits表中，查询f_name字段值以字母’b’开头，且’b’后面出现字母’a’的记录 MysqL> SELECT * FROM fruits WHERE f_name REGEXP '^ba*'; +------+------+------------+---------+ | f_id | s_id | f_name | f_price | +------+------+------------+---------+ | b1 | 101 | blackBerry | 10.20 | | b2 | 104 | Berry | 7.60 | | t1 | 102 | banana | 10.30 | +------+------+------------+---------+ 3 rows in set (0.00 sec) 在fruits表中，查询f_name字段值以字母’b’开头，且’b’后面出现字母’a’至少一次的记录 MysqL> SELECT * FROM fruits WHERE f_name REGEXP '^ba+'; +------+------+--------+---------+ | f_id | s_id | f_name | f_price | +------+------+--------+---------+ | t1 | 102 | banana | 10.30 | +------+------+--------+---------+ 1 row in set (0.00 sec) 在fruits表中，查询f_name字段值包含字符串“on”的记录 MysqL> SELECT * FROM fruits WHERE f_name REGEXP 'on'; +------+------+---------+---------+ | f_id | s_id | f_name | f_price | +------+------+---------+---------+ | bs2 | 105 | melon | 8.20 | | l2 | 104 | lemon | 6.40 | | o2 | 103 | coconut | 9.20 | +------+------+---------+---------+ 3 rows in set (0.00 sec) 在fruits表中，查询f_name字段值包含字符串“on”或者“ap”的记录 MysqL> SELECT * FROM fruits WHERE f_name REGEXP 'on|ap'; +------+------+---------+---------+ | f_id | s_id | f_name | f_price | +------+------+---------+---------+ | a1 | 101 | apple | 5.20 | | a2 | 103 | apricot | 2.20 | | bs2 | 105 | melon | 8.20 | | l2 | 104 | lemon | 6.40 | | o2 | 103 | coconut | 9.20 | | t2 | 102 | grape | 5.30 | +------+------+---------+---------+ 6 rows in set (0.00 sec) 在fruits表中，使用LIKE运算符查询f_name字段值为“on”的记录 MysqL> SELECT * FROM fruits WHERE f_name LIKE 'on'; Empty set (0.00 sec) 在fruits表中，查找f_name字段中包含字母’o’或者’t’的记录 MysqL> SELECT * FROM fruits WHERE f_name REGEXP '[ot]'; +------+------+---------+---------+ | f_id | s_id | f_name | f_price | +------+------+---------+---------+ | a2 | 103 | apricot | 2.20 | | bs1 | 102 | orange | 11.20 | | bs2 | 105 | melon | 8.20 | | l2 | 104 | lemon | 6.40 | | m1 | 106 | mango | 15.60 | | m3 | 105 | xxtt | 11.60 | | o2 | 103 | coconut | 9.20 | +------+------+---------+---------+ 7 rows in set (0.00 sec) 在fruits表，查询s_id字段中数值中包含4、5或者6的记录 MysqL> SELECT * FROM fruits WHERE s_id REGEXP '[456]'; +------+------+--------+---------+ | f_id | s_id | f_name | f_price | +------+------+--------+---------+ | b2 | 104 | Berry | 7.60 | | bs2 | 105 | melon | 8.20 | | l2 | 104 | lemon | 6.40 | | m1 | 106 | mango | 15.60 | | m2 | 105 | xbabay | 2.60 | | m3 | 105 | xxtt | 11.60 | +------+------+--------+---------+ 6 rows in set (0.00 sec) 在fruits表中，查询f_id字段包含字母a~e和数字1~2以外的字符的记录 MysqL> SELECT * FROM fruits WHERE f_id REGEXP '[^a-e1-2]'; +------+------+---------+---------+ | f_id | s_id | f_name | f_price | +------+------+---------+---------+ | b5 | 107 | xxxx | 3.60 | | bs1 | 102 | orange | 11.20 | | bs2 | 105 | melon | 8.20 | | c0 | 101 | cherry | 3.20 | | l2 | 104 | lemon | 6.40 | | m1 | 106 | mango | 15.60 | | m2 | 105 | xbabay | 2.60 | | m3 | 105 | xxtt | 11.60 | | o2 | 103 | coconut | 9.20 | | t1 | 102 | banana | 10.30 | | t2 | 102 | grape | 5.30 | | t4 | 107 | xbababa | 3.60 | +------+------+---------+---------+ 12 rows in set (0.00 sec) 在fruits表中，查询f_name字段值出现字母’x’至少2次的记录 MysqL> SELECT * FROM fruits WHERE f_name REGEXP 'x{2,}'; +------+------+--------+---------+ | f_id | s_id | f_name | f_price | +------+------+--------+---------+ | b5 | 107 | xxxx | 3.60 | | m3 | 105 | xxtt | 11.60 | +------+------+--------+---------+ 2 rows in set (0.00 sec) 在fruits表中，查询f_name字段值出现字符串“ba”最少1次，最多3次的记录 MysqL> SELECT * FROM fruits WHERE f_name REGEXP 'ba{1,3}'; +------+------+---------+---------+ | f_id | s_id | f_name | f_price | +------+------+---------+---------+ | m2 | 105 | xbabay | 2.60 | | t1 | 102 | banana | 10.30 | | t4 | 107 | xbababa | 3.60 | +------+------+---------+---------+ 3 rows in set (0.00 sec)
