存储在系统中的数据是数据库管理系统(DBMS)的核心，数据库被设计用来管理数据的存储、访问和维护数据的完整性。MySQL中提供丰富的数据管理语句，包括插入数据的INSERT、更新数据的UPDATE以及删除数据的DELETE语句。
7.1、插入数据
为表的所有字段插入数据
使用基本的INSERT语句插入数据，要求指定表名称和插入到新纪录中的值，其基本语法为：
INSERT INTO tbl_name (column_list) VALUES (value_list)
在插入数据前，首先创建一张表：
mysql> CREATE TABLE person -> ( -> id INT UNSIGNED NOT NULL AUTO_INCREMENT, -> name CHAR(40) NOT NULL DEFAULT '', -> age INT NOT NULL DEFAULT 0, -> info CHAR(50) NULL, -> PRIMARY KEY (id) -> ); Query OK, 0 rows affected (0.03 sec)
在person表中，插入一条新记录，id值为1，name值为Green，age值为21，info值为Lawyer
mysql> INSERT INTO person (id ,name, age , info) -> VALUES (1,'Green', 21, 'Lawyer'); Query OK, 1 row affected (0.02 sec) mysql> SELECT * FROM person; +----+-------+-----+--------+ | id | name | age | info | +----+-------+-----+--------+ | 1 | Green | 21 | Lawyer | +----+-------+-----+--------+ 1 row in set (0.00 sec)
在person表中，插入一条新记录，id值为2，name值为Suse，age值为22，info值为dancer
mysql> INSERT INTO person (age ,name, id , info) -> VALUES (22, 'Suse', 2, 'dancer'); Query OK, 1 row affected (0.02 sec) mysql> SELECT * FROM person; +----+-------+-----+--------+ | id | name | age | info | +----+-------+-----+--------+ | 1 | Green | 21 | Lawyer | | 2 | Suse | 22 | dancer | +----+-------+-----+--------+ 2 rows in set (0.00 sec)
为表的指定字段插入数据
在person表中，插入一条新记录，name值为Willam，age值为20，info值为sports man
mysql> INSERT INTO person (name, age,info)
-> VALUES('Willam', 20, 'sports man');
Query OK, 1 row affected (0.02 sec)
mysql> SELECT * FROM person;
+----+--------+-----+------------+
| id | name | age | info |
+----+--------+-----+------------+
| 1 | Green | 21 | Lawyer |
| 2 | Suse | 22 | dancer |
| 3 | Willam | 20 | sports man |
+----+--------+-----+------------+
3 rows in set (0.00 sec)在person表中，插入一条新记录，name值为laura，age值为25
mysql> INSERT INTO person (name, age ) VALUES ('Laura', 25);
Query OK, 1 row affected (0.01 sec)
mysql> SELECT * FROM person;
+----+--------+-----+------------+
| id | name | age | info |
+----+--------+-----+------------+
| 1 | Green | 21 | Lawyer |
| 2 | Suse | 22 | dancer |
| 3 | Willam | 20 | sports man |
| 4 | Laura | 25 | NULL |
+----+--------+-----+------------+
4 rows in set (0.00 sec)可以发现id字段在插入数据后，没有赋值时自动增加，在这里id字段为表的主键，不能为空，紫铜会自动为字段插入自增的序列值。
同时插入多条记录
INSERT语句可以同时相数据表中插入多条记录，插入时指定多个值列表，每个值列表之间用逗号分隔开，基本语法为：
INSERT INTO tbl_name (column_list) VALUES (value_list1), (value_list2),(value_list3);
在person表中，在name、age和info字段指定插入值，同时插入3条新记录
mysql> INSERT INTO person(name, age, info)
-> VALUES ('Evans',27, 'secretary'),
-> ('Dale',22, 'cook'),
-> ('Edison',28, 'singer');
Query OK, 3 rows affected (0.02 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> SELECT * FROM person;
+----+--------+-----+------------+
| id | name | age | info |
+----+--------+-----+------------+
| 1 | Green | 21 | Lawyer |
| 2 | Suse | 22 | dancer |
| 3 | Willam | 20 | sports man |
| 4 | Laura | 25 | NULL |
| 5 | Evans | 27 | secretary |
| 6 | Dale | 22 | cook |
| 7 | Edison | 28 | singer |
+----+--------+-----+------------+
7 rows in set (0.00 sec)在person表中，不指定插入列表，同时插入2条新记录
mysql> INSERT INTO person -> VALUES (9,'Harry',21, 'magician'), -> (NULL,'Harriet',19, 'pianist'); Query OK, 2 rows affected (0.02 sec) Records: 2 Duplicates: 0 Warnings: 0 mysql> SELECT * FROM person; +----+---------+-----+------------+ | id | name | age | info | +----+---------+-----+------------+ | 1 | Green | 21 | Lawyer | | 2 | Suse | 22 | dancer | | 3 | Willam | 20 | sports man | | 4 | Laura | 25 | NULL | | 5 | Evans | 27 | secretary | | 6 | Dale | 22 | cook | | 7 | Edison | 28 | singer | | 9 | Harry | 21 | magician | | 10 | Harriet | 19 | pianist | +----+---------+-----+------------+ 9 rows in set (0.00 sec)
将查询结果插入数据
INSERT语句用来给数据表插入记录时，指定插入记录的列值。INSERT还可以将SELECT语句查询的结果插入到列表中，其基本语法为：
INSERT INTO tbl_name1 (column_list1) SELECT (column_list2) FROM table_name2 WHERE (condition)
从person_old表中查询所有的记录，并将其插入到person表中
首先，创建一个名为person_old的数据表，其表结构与person结构相同 mysql> CREATE TABLE person_old -> ( -> id INT UNSIGNED NOT NULL AUTO_INCREMENT, -> name CHAR(40) NOT NULL DEFAULT '', -> age INT NOT NULL DEFAULT 0, -> info CHAR(50) NULL, -> PRIMARY KEY (id) -> ); Query OK, 0 rows affected (0.11 sec) 向person_old表中添加两条记录 mysql> INSERT INTO person_old -> VALUES (11,'Harry',20, 'student'), (12,'Beckham',31, 'police'); Query OK, 2 rows affected (0.20 sec) Records: 2 Duplicates: 0 Warnings: 0 mysql> SELECT * FROM person_old; +----+---------+-----+---------+ | id | name | age | info | +----+---------+-----+---------+ | 11 | Harry | 20 | student | | 12 | Beckham | 31 | police | +----+---------+-----+---------+ 2 rows in set (0.00 sec) 插入数据到person表中 mysql> INSERT INTO person(id, name, age, info) -> SELECT id, name, age, info FROM person_old; Query OK, 2 rows affected (0.01 sec) Records: 2 Duplicates: 0 Warnings: 0 mysql> SELECT * FROM person; +----+---------+-----+------------+ | id | name | age | info | +----+---------+-----+------------+ | 1 | Green | 21 | Lawyer | | 2 | Suse | 22 | dancer | | 3 | Willam | 20 | sports man | | 4 | Laura | 25 | NULL | | 5 | Evans | 27 | secretary | | 6 | Dale | 22 | cook | | 7 | Edison | 28 | singer | | 9 | Harry | 21 | magician | | 10 | Harriet | 19 | pianist | | 11 | Harry | 20 | student | | 12 | Beckham | 31 | police | +----+---------+-----+------------+ 11 rows in set (0.00 sec)
7.2、更新数据
表中有数据之后，可以对数据进行更新，其基本语法为：
UPDATE table_name SET col_name1=value1,col_name2=value2,..., WHERE where_condition
在person表中，更新id值为11的记录，将age字段值改为15，将name字段值改为LiMing
mysql> UPDATE person SET age = 15, name='LiMing' WHERE id = 11; Query OK, 1 row affected (0.02 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> SELECT * FROM person WHERE id=11; +----+--------+-----+---------+ | id | name | age | info | +----+--------+-----+---------+ | 11 | LiMing | 15 | student | +----+--------+-----+---------+ 1 row in set (0.00 sec)
在person表中，更新age值为19~22的记录，将info字段值都改为student
mysql> UPDATE person SET info='student' WHERE age BETWEEN 19 AND 22; Query OK, 6 rows affected (0.02 sec) Rows matched: 6 Changed: 6 Warnings: 0 mysql> SELECT * FROM person WHERE age BETWEEN 19 AND 22; +----+---------+-----+---------+ | id | name | age | info | +----+---------+-----+---------+ | 1 | Green | 21 | student | | 2 | Suse | 22 | student | | 3 | Willam | 20 | student | | 6 | Dale | 22 | student | | 9 | Harry | 21 | student | | 10 | Harriet | 19 | student | +----+---------+-----+---------+ 6 rows in set (0.00 sec)
7.3、删除数据
从数据表中删除数据使用DELETE语句，其基本语法为：
DELETE FROMN table_name [WHERE <condition>]
在person表中，删除id等于11的记录
执行删除操作前，使用SELECT语句查看当前id=11的记录 mysql> SELECT * FROM person WHERE id=11; +----+--------+-----+---------+ | id | name | age | info | +----+--------+-----+---------+ | 11 | LiMing | 15 | student | +----+--------+-----+---------+ 1 row in set (0.00 sec) 使用DELETE语句删除该记录 mysql> DELETE FROM person WHERE id = 11; Query OK, 1 row affected (0.02 sec) 语句执行完毕，查看执行结果： mysql> SELECT * FROM person WHERE id=11; Empty set (0.00 sec)
在person表中，使用DELETE语句同时删除多条记录，删除age字段在19-22的记录
执行删除操作前，使用SELECT语句查看当前的数据 mysql> SELECT * FROM person WHERE age BETWEEN 19 AND 22; +----+---------+-----+---------+ | id | name | age | info | +----+---------+-----+---------+ | 1 | Green | 21 | student | | 2 | Suse | 22 | student | | 3 | Willam | 20 | student | | 6 | Dale | 22 | student | | 9 | Harry | 21 | student | | 10 | Harriet | 19 | student | +----+---------+-----+---------+ 6 rows in set (0.00 sec) DELETE删除这些记录 mysql> DELETE FROM person WHERE age BETWEEN 19 AND 22; Query OK, 6 rows affected (0.01 sec) 查看执行结果 mysql> SELECT * FROM person WHERE age BETWEEN 19 AND 22; Empty set (0.00 sec)
删除person表中所有记录，SQL语句如下
执行删除操作前，使用SELECT语句查看当前的数据： mysql> SELECT * FROM person; +----+---------+-----+-----------+ | id | name | age | info | +----+---------+-----+-----------+ | 4 | Laura | 25 | NULL | | 5 | Evans | 27 | secretary | | 7 | Edison | 28 | singer | | 12 | Beckham | 31 | police | +----+---------+-----+-----------+ 4 rows in set (0.00 sec) 执行DELETE语句删除这4条记录 mysql> DELETE FROM person; Query OK, 4 rows affected (0.01 sec) 查看执行结果： mysql> SELECT * FROM person; Empty set (0.00 sec)
如果想删除表中的所有记录，还可以使用TRUNCATE TABLE语句，TRUNCATE将直接删除原来的表并重新创建一个表，其语法结构为TRUNCATE TABLE table_name。TRUNCATE直接删除表而不是删除记录，因此执行速度比DELETE快。
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