4 SQL语言基础-2
1、向表格中插入数据，查询数据
向表格中插入 一条记录：INSERT INTO tablename VALUES (值1，值2，、、、）
或INSERT INTO tablename(列1，列2、、、） VAlues(值1,值2、、、）；
2、从表格中查询记录：SELECT * FROM tablename; #查询表中所有数据
或SELECT 列名称1，列名称2、、、 FROM tablename; #查询表中指定数据
mysql> INSERT INTO course VALUES(1,'linux',45,'basic'); Query OK, 1 row affected (0.00 sec) mysql> INSERT INTO course(idid,course_length) VALUES(2,40) -> ; Query OK, 1 row affected (0.00 sec) mysql> SELECT * FROM course -> ; +------+-------------+---------------+----------+ | idid | course_name | course_length | category | +------+-------------+---------------+----------+ | 1 | linux | 45 | basic | | 2 | NULL | 40 | NULL | +------+-------------+---------------+----------+ 2 rows in set (0.00 sec) mysql> SELECT idid,course_name,course_length -> ; ERROR 1054 (42S22): Unknown column 'idid' in 'field list' mysql> SELECT idid,course_name, course_length FROM course; +------+-------------+---------------+ | idid | course_name | course_length | +------+-------------+---------------+ | 1 | linux | 45 | | 2 | NULL | 40 | +------+-------------+---------------+ 2 rows in set (0.00 sec) mysql> mysql> use mysql Database changed mysql> show tables; +---------------------------+ | Tables_in_mysql | +---------------------------+ | columns_priv | | db | | event | | func | | general_log | | help_category | | help_keyword | | help_relation | | help_topic | | host | | ndb_binlog_index | | plugin | | proc | | procs_priv | | servers | | slow_log | | tables_priv | | time_zone | | time_zone_leap_second | | time_zone_name | | time_zone_transition | | time_zone_transition_type | | user | +---------------------------+ 23 rows in set (0.00 sec) mysql> SELECT * FORM user; #查看数据库的所有用户 ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'FORM user' at line 1 mysql> SELECT * FRoM user; +-----------------------+------+-------------------------------------------+-------------+-------------+-------------+-------------+-------------+-----------+-------------+---------------+--------------+-----------+------------+-----------------+------------+------------+--------------+------------+-----------------------+------------------+--------------+-----------------+------------------+------------------+----------------+---------------------+--------------------+------------------+------------+--------------+----------+------------+-------------+--------------+---------------+-------------+-----------------+----------------------+ | Host | User | Password | Select_priv | Insert_priv | Update_priv | Delete_priv | Create_priv | Drop_priv | Reload_priv | Shutdown_priv | Process_priv | File_priv | Grant_priv | References_priv | Index_priv | Alter_priv | Show_db_priv | Super_priv | Create_tmp_table_priv | Lock_tables_priv | Execute_priv | Repl_slave_priv | Repl_client_priv | Create_view_priv | Show_view_priv | Create_routine_priv | Alter_routine_priv | Create_user_priv | Event_priv | Trigger_priv | ssl_type | ssl_cipher | x509_issuer | x509_subject | max_questions | max_updates | max_connections | max_user_connections | +-----------------------+------+-------------------------------------------+-------------+-------------+-------------+-------------+-------------+-----------+-------------+---------------+--------------+-----------+------------+-----------------+------------+------------+--------------+------------+-----------------------+------------------+--------------+-----------------+------------------+------------------+----------------+---------------------+--------------------+------------------+------------+--------------+----------+------------+-------------+--------------+---------------+-------------+-----------------+----------------------+ | localhost | root | *6A7A490FB9DC8C33C2B025A91737077A7E9CC5E5 | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | | | | | 0 | 0 | 0 | 0 | | localhost.localdomain | root | | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | | | | | 0 | 0 | 0 | 0 | | 127.0.0.1 | root | | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | | | | | 0 | 0 | 0 | 0 | | localhost | | | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | | | | | 0 | 0 | 0 | 0 | | localhost.localdomain | | | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | | | | | 0 | 0 | 0 | 0 | +-----------------------+------+-------------------------------------------+-------------+-------------+-------------+-------------+-------------+-----------+-------------+---------------+--------------+-----------+------------+-----------------+------------+------------+--------------+------------+-----------------------+------------------+--------------+-----------------+------------------+------------------+----------------+---------------------+--------------------+------------------+------------+--------------+----------+------------+-------------+--------------+---------------+-------------+-----------------+----------------------+ 5 rows in set (0.00 sec) mysql> select user,host,password from user; #查看数据库的所有用户，所在主机，密码 +------+-----------------------+-------------------------------------------+ | user | host | password | +------+-----------------------+-------------------------------------------+ | root | localhost | *6A7A490FB9DC8C33C2B025A91737077A7E9CC5E5 | | root | localhost.localdomain | | | root | 127.0.0.1 | | | | localhost | | | | localhost.localdomain | | +------+-----------------------+-------------------------------------------+ 5 rows in set (0.00 sec) mysql>
按条件查询数据：
从表格中按条件查询一条记录：SELECT 列名称或* FROM 表名 WHERE 列 运算符 值；
mysql> desc course; +---------------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +---------------+-------------+------+-----+---------+-------+ | idid | int(12) | YES | | NULL | | | course_name | varchar(50) | YES | | NULL | | | course_length | int(11) | YES | | NULL | | | category | varchar(50) | YES | | NULL | | +---------------+-------------+------+-----+---------+-------+ 4 rows in set (0.13 sec) mysql> select * from course; +------+-------------+---------------+----------+ | idid | course_name | course_length | category | +------+-------------+---------------+----------+ | 1 | linux | 45 | basic | | 2 | NULL | 40 | NULL | +------+-------------+---------------+----------+ 2 rows in set (0.00 sec) mysql> select course_length from course; +---------------+ | course_length | +---------------+ | 45 | | 40 | +---------------+ 2 rows in set (0.00 sec) mysql> select course_length from course where course_length>40; #按课程时间 +---------------+ | course_length | +---------------+ | 45 | +---------------+ 1 row in set (0.11 sec) mysql> select * from course where course_name='linux'; #按课程名称 +------+-------------+---------------+----------+ | idid | course_name | course_length | category | +------+-------------+---------------+----------+ | 1 | linux | 45 | basic | +------+-------------+---------------+----------+ 1 row in set (0.08 sec) mysql> select course_name from course where course_name='linux'; +-------------+ | course_name | +-------------+ | linux | +-------------+ 1 row in set (0.00 sec) mysql>
SQL WHERE支持的运算符
操作符 功能
= 等于
<> 不等于
>
<
>=
<=
BETWEEN 在某范围内
LIKE 搜索某种模式
3、从表中删除一条记录：DELETE FROM 表名称 WHERE 列 运算符 值；
DELETE * FROM 表名； #删除表中所有信息
mysql> select * from course; +------+-------------+---------------+----------+ | idid | course_name | course_length | category | +------+-------------+---------------+----------+ | 1 | linux | 45 | basic | | 2 | NULL | 40 | NULL | +------+-------------+---------------+----------+ 2 rows in set (0.00 sec) mysql> delete from course where course_length=40; Query OK, 1 row affected (0.06 sec) mysql> select * from course; +------+-------------+---------------+----------+ | idid | course_name | course_length | category | +------+-------------+---------------+----------+ | 1 | linux | 45 | basic | +------+-------------+---------------+----------+ 1 row in set (0.00 sec) mysql>
4、从表中更新 一条记录：UPDATE 表名 SET 列名称=新值 WHERE 列=值；
mysql> select * from course; +------+-------------+---------------+----------+ | idid | course_name | course_length | category | +------+-------------+---------------+----------+ | 1 | linux | 45 | basic | +------+-------------+---------------+----------+ 1 row in set (0.00 sec) mysql> UPDATE course SET course_length=60 where idid=1; Query OK, 1 row affected (0.10 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> select * from course; +------+-------------+---------------+----------+ | idid | course_name | course_length | category | +------+-------------+---------------+----------+ | 1 | linux | 60 | basic | +------+-------------+---------------+----------+ 1 row in set (0.00 sec) mysql> update course set course_name='linuxs',course_length=100 where idid=1; Query OK, 1 row affected (0.06 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> select * from course; +------+-------------+---------------+----------+ | idid | course_name | course_length | category | +------+-------------+---------------+----------+ | 1 | linuxs | 100 | basic | +------+-------------+---------------+----------+ 1 row in set (0.00 sec) mysql>
5、删除返回结果重复项：SELECT DISTINCT 列名称 FROM 表名；
WHERE条件中使用逻辑组合：SELECT * FROM 表名称 Where 条件1 AND或OR 条件2；
对查询结果按指定列进行排序：SELECT * FROM 表名称 ORDER BY 别名称； #默认从小到大
对查询结果按指定列进行排序：SELECT * FROM 表名称 ORDER BY 别名称 DESC； #倒序