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: 0mysql> 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: 0mysql> 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: 0mysql> 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: 0mysql> 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: 0mysql> 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: 0mysql> 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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