MySQL学习笔记-操作数据表中的记录
1.插入记录 INSERT
INSERT [INTO] tbl_name [(col_name,...)] {VAULES|VALUE} ({expr|DEFAULT},...),(...),...例，插入单条记录：
mysql> USE testDatabase changed
mysql> CREATE TABLE users( -> id SMALLINT UNSIGNED AUTO_INCREMENT PRIMARY KEY, -> username VARCHAR(20) NOT NULL, -> password VARCHAR(32) NOT NULL, -> age TINYINT UNSIGNED NOT NULL DEFAULT 10, -> sex BOOLEAN -> );
mysql> INSERT users VALUES(NULL,'Tom','asd123',24,1);
mysql> SELECT * FROM users;+----+----------+----------+-----+------+| id | username | password | age | sex |+----+----------+----------+-----+------+| 1 | Tom | asd123 | 24 | 1 |+----+----------+----------+-----+------+
插入多条记录：
mysql> INSERT users VALUES(DEFAULT,'John','asd123',24,1), -> (NULL,'Huang','daddd',25,1);
mysql> SELECT * FROM users;
+----+----------+----------+-----+------+| id | username | password | age | sex |+----+----------+----------+-----+------+| 1 | Tom | asd123 | 24 | 1 || 2 | John | asd123 | 24 | 1 || 3 | Huang | daddd | 25 | 1 |+----+----------+----------+-----+------+
插入数学表达式：
mysql> INSERT users VALUES(NULL,'John','asd123',3*7-5,1);
mysql> SELECT * FROM users;+----+----------+----------+-----+------+| id | username | password | age | sex |+----+----------+----------+-----+------+| 1 | Tom | asd123 | 24 | 1 || 2 | John | asd123 | 24 | 1 || 3 | Huang | daddd | 25 | 1 || 4 | John | asd123 | 16 | 1 |+----+----------+----------+-----+------+
插入md5的哈希密码：
mysql> INSERT users VALUES(NULL,'John',md5('123'),DEFAULT,0)；
mysql> SELECT * FROM users;+----+----------+----------------------------------+-----+------+| id | username | password | age | sex |+----+----------+----------------------------------+-----+------+| 1 | Tom | asd123 | 24 | 1 || 2 | John | asd123 | 24 | 1 || 3 | Huang | daddd | 25 | 1 || 4 | John | asd123 | 16 | 1 || 5 | John | 202cb962ac59075b964b07152d234b70 | 10 | 0 |+----+----------+----------------------------------+-----+------+
2.插入记录 INSERT SET-SELECT
(与第一种方式的区别是 可以使用子查询，不可以同时插入多条记录)
INSERT [INTO] tbl_name SET col_name={expr|DEFAULT},...
例：
mysql> INSERT users SET username='Ben',password=md5('345');
mysql> SELECT * FROM users;+----+----------------------+----------------------------------+-----+------+| id | username | password | age | sex |+----+----------------------+----------------------------------+-----+------+| 1 | Tom | asd123 | 24 | 1 || 2 | John | asd123 | 24 | 1 || 3 | Huang | daddd | 25 | 1 || 4 | John | asd123 | 16 | 1 || 5 | John | 202cb962ac59075b964b07152d234b70 | 10 | 0 || 6 | Ben | d81f9c1be2e08964bf9f24b15f0e4900 | 10 | NULL |+----+----------------------+----------------------------------+-----+------+
3.更新记录 UPDATE
单表更新
UPDATE [LOW_PRIORITY] [IGNORE] table_reference SET col_name1={expr1|DEFAULT} [,col_name2={expr2|DEFAULT}]... [WHERE where_condition]
例，将所有记录的年龄加5：
mysql> UPDATE users SET age = age+5;
mysql> SELECT * FROM users;
+----+----------------------+----------------------------------+-----+------+| id | username | password | age | sex |+----+----------------------+----------------------------------+-----+------+| 1 | Tom | asd123 | 29 | 1 || 2 | John | asd123 | 29 | 1 || 3 | Huang | daddd | 30 | 1 || 4 | John | asd123 | 21 | 1 || 5 | John | 202cb962ac59075b964b07152d234b70 | 15 | 0 || 6 | Ben | d81f9c1be2e08964bf9f24b15f0e4900 | 15 | NULL |+----+----------------------+----------------------------------+-----+------+
将Tom的年龄加10岁：
mysql> UPDATE users SET age = age+10 WHERE id=1;
mysql> SELECT * FROM users WHERE id=1;+----+----------+----------+-----+------+| id | username | password | age | sex |+----+----------+----------+-----+------+| 1 | Tom | asd123 | 39 | 1 |+----+----------+----------+-----+------+
将id为偶数的年龄加10岁：
mysql> UPDATE users SET age = age+10 WHERE id % 2 = 0;
mysql> select * from users;
+----+----------------------+----------------------------------+-----+------+| id | username | password | age | sex |+----+----------------------+----------------------------------+-----+------+| 1 | Tom | asd123 | 39 | 1 || 2 | John | asd123 | 39 | 1 || 3 | Huang | daddd | 30 | 1 || 4 | John | asd123 | 31 | 1 || 5 | John | 202cb962ac59075b964b07152d234b70 | 15 | 0 |+----+----------------------+----------------------------------+-----+------+
修改所有记录的sex为0：
mysql> UPDATE users SET sex = 0；
mysql> select * from users;
+----+----------------------+----------------------------------+-----+------+| id | username | password | age | sex |+----+----------------------+----------------------------------+-----+------+| 1 | Tom | asd123 | 39 | 0 || 2 | John | asd123 | 39 | 0 || 3 | Huang | daddd | 30 | 0 || 4 | John | asd123 | 31 | 0 || 5 | John | 202cb962ac59075b964b07152d234b70 | 15 | 0 || 7 | Ben | d81f9c1be2e08964bf9f24b15f0e4900 | 15 | 0 |+----+----------------------+----------------------------------+-----+------+
4.删除记录 DELETE
单表删除 (若不添加WHERE则删除【全部记录】)
DELETE FROM tbl_name [WHERE where_condition]
例，删除id=7的记录：
mysql> DELETE FROM users WHERE id = 7;
mysql> select * from users;
+----+----------+----------------------------------+-----+------+| id | username | password | age | sex |+----+----------+----------------------------------+-----+------+| 1 | Tom | asd123 | 39 | 0 || 2 | John | asd123 | 39 | 0 || 3 | Huang | daddd | 30 | 0 || 4 | John | asd123 | 31 | 0 || 5 | John | 202cb962ac59075b964b07152d234b70 | 15 | 0 |+----+----------+----------------------------------+-----+------+
5.查找记录 SELECT
SELECT select_expr [,select_expr...][
FROM tbl_references
[WHERE where_condition]
[GROUP BY {col_name | position} [ASC | DESC],...] [HAVING where_condition]
[ORDER BY {col_name | expo | position} [ASC | DESC],...] [LIMIT {[offset,] row_count | row_count OFFSET offset}]
]
查询表达式（select_expr）
1. 每一个表达式表示想要的一列，必须有至少一个
2. 多个列之间以英文逗号分隔
3. 星号（*）表示所有列；tbl_name.*可以表示命名表的所有列
4. 查询表达式可以使用[AS]alias_name为其赋予别名
5. 别名可用于GROUP BY，ORDER BY或HAVING子句
SELECT查询表达式字段出现的顺序将影响结果集字段出现的顺序
字段的别名也会影响以后的结果集 , 在以后的PHP中有重要作用
例，只查询users表中 id 和 username 两列：
mysql> SELECT id,username FROM users;+----+----------+| id | username |+----+----------+| 1 | Tom || 2 | John || 3 | Huang || 4 | John || 5 | John |+----+----------+
查询users表中 id 和 username 两列，分别用userid，uname作为别名：
mysql> SELECT id AS userid ,username AS uname FROM users;
+--------+-------+| userid | uname |+--------+-------+| 1 | Tom || 2 | John || 3 | Huang || 4 | John || 5 | John |+--------+-------+
6.where语句进行条件查询
条件表达式（WHERE）
对记录进行过滤，如果没有指定WHERE子句，则显示所有记录
在WHERE表达式中，可以使用MySQL支持的函数或运算符
7.group by语句对查询结果分组
group by
查询结果分组
[GROUP BY {col_name | position} [ASC | DESC],...]
可以制定列的列名和列的位置。
asc生序，desc降序，多个分组中间用逗号区分。
例，查询users表，按照性别分组：
mysql> SELECT sex FROM users GROUP BY sex;+------+| sex |+------+| 0 |+------+
8.having语句设置分组条件
分组条件（HAVING）
[HAVING where_condition]
其中，where_condition要么是聚合函数（max,min,avg,count,sum），要么其中的字段必须是SELECT中的一个查询字段，否则会报错]
例，查询users表中sex分组，条件为age>20（这种方法需要查询字段也添加age字段）：
mysql> SELECT sex,age FROM users GROUP BY sex having age > 20;
+------+-----+| sex | age |+------+-----+| 0 | 39 |+------+-----+
查询users表中sex分组，条件为id >=2 :
mysql> SELECT sex FROM users GROUP BY sex HAVING count(id) >= 2;
+------+| sex |+------+| 0 |+------+
9.order by语句对查询结果排序
对查询结果进行排序（ORDER BY）
[ORDER BY {col_name | expr | position} [ASC | DESC],...]
可以按照多个列排序
例，查询users表，按年龄从小到大排列：
mysql> SELECT * FROM users ORDER BY age ASC;
+----+----------+----------------------------------+-----+------+| id | username | password | age | sex |+----+----------+----------------------------------+-----+------+| 8 | Hui | 9e1e06ec8e02f0a0074f2fcc6b26303b | 8 | 1 || 5 | John | 202cb962ac59075b964b07152d234b70 | 15 | 0 || 10 | Luyuan | 9e1e06ec8e02f0a0074f2fcc6b26303b | 21 | 1 || 9 | Dui | 9e1e06ec8e02f0a0074f2fcc6b26303b | 27 | 1 || 3 | Huang | daddd | 30 | 0 || 12 | Murouan | 9e1e06ec8e02f0a0074f2fcc6b26303b | 31 | 1 || 11 | Oduyuan | 9e1e06ec8e02f0a0074f2fcc6b26303b | 31 | 1 || 13 | Spqoan | 9e1e06ec8e02f0a0074f2fcc6b26303b | 31 | 1 || 4 | John | asd123 | 31 | 0 || 2 | John | asd123 | 39 | 0 || 1 | Tom | asd123 | 39 | 0 |+----+----------+----------------------------------+-----+------+
查询users表，第一顺序按年龄从小到大排列，第二顺序按id从小到大排列：
mysql> SELECT * FROM users ORDER BY age,id ASC;+----+----------+----------------------------------+-----+------+| id | username | password | age | sex |+----+----------+----------------------------------+-----+------+| 8 | Hui | 9e1e06ec8e02f0a0074f2fcc6b26303b | 8 | 1 || 5 | John | 202cb962ac59075b964b07152d234b70 | 15 | 0 || 10 | Luyuan | 9e1e06ec8e02f0a0074f2fcc6b26303b | 21 | 1 || 9 | Dui | 9e1e06ec8e02f0a0074f2fcc6b26303b | 27 | 1 || 3 | Huang | daddd | 30 | 0 || 4 | John | asd123 | 31 | 0 || 11 | Oduyuan | 9e1e06ec8e02f0a0074f2fcc6b26303b | 31 | 1 || 12 | Murouan | 9e1e06ec8e02f0a0074f2fcc6b26303b | 31 | 1 || 13 | Spqoan | 9e1e06ec8e02f0a0074f2fcc6b26303b | 31 | 1 || 1 | Tom | asd123 | 39 | 0 || 2 | John | asd123 | 39 | 0 |+----+----------+----------------------------------+-----+------+
10.LIMIT语句限制查询数量
LIMIT 限制查询结果返回的数量
[LIMIT{[offset,]row_count|row_count OFFSET offset}]
SELECT * from users #返回所有的结果
SELECT * from users limit 2 #返回所有的结果集中前两条
mysql> SELECT * FROM users LIMIT 2;+----+----------+----------+-----+------+| id | username | password | age | sex |+----+----------+----------+-----+------+| 1 | Tom | asd123 | 39 | 0 || 2 | John | asd123 | 39 | 0 |+----+----------+----------+-----+------+
SELECT * FROM users LIMIT 2,2; #要查询结果集中第3条和第4条记录。mysql中的记录是从0开始的，共几条。
mysql> SELECT * FROM users LIMIT 2,2;+----+----------+----------+-----+------+| id | username | password | age | sex |+----+----------+----------+-----+------+| 3 | Huang | daddd | 30 | 0 || 4 | John | asd123 | 31 | 0 |+----+----------+----------+-----+------+
总结
记录操作: INSERT , UPDATE , DELETE , SELECT
1.insert的三种
insert [into] 表名 [(列名,列名)]{values|value} ({（表达式|default},（）)insert [into] 表名 set 列名={（表达式|default}，。。insert [into] 表名 [(列名,列名)] SELECT..
2.UPDATE
（1）单表更新
UPDATE [LOW_PRIORITY][IGNORE] table_reference SET col_name1={expr1|DEFAULT},[col_name2={expr2|DEFAULT}]...[WHERE where_condition]
多表更新
3.DELETE : 删除数据
（1）单表删除
DELETE FROM tbl_name [WHERE where_condition}
4.SELECT: //查询
SELECT select_expr [,select expr2...] #只查找某一个函数或表达式[FROM table_references #查询表名[WHERE where_conditon] #查询条件[GROUP BY {col_name|position} [ASC|DESC],...] #按某个字段进行分组，相同的只显示第一个[HAVING where_conditon] #分组时，给出显示条件[ORDER BY {col_name|expr|position} [ASC|DESC],...] #排序[LIMIT {[offset,]row_count|row_count OFFSET offset}] #限制返回数量]
SELECT
FROM 表的参照
WHERE 条件
GROUP BY 对记录结果进行分组
HAVING 对分组条件的设定
结合内容，将查找的结果存储在指定的数据表：
mysql> CREATE TABLE test( -> id TINYINT UNSIGNED PRIMARY KEY AUTO_INCREMENT, -> username VARCHAR(20) NOT NULL
-> );
mysql> INSERT test(username) SELECT username FROM users WHERE age >= 25;
mysql> SELECT * FROM test;
+----+----------+| id | username |+----+----------+| 1 | Tom || 2 | John || 3 | Huang || 4 | John || 5 | Dui || 6 | Oduyuan || 7 | Murouan || 8 | Spqoan |+----+----------+
来源：oschina
链接：https://my.oschina.net/u/4279277/blog/4841733