一：显示数据库及模糊查询（like）
sql
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| db_classes |
| db_user |
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
6 rows in set (0.00 sec)
mysql> show databases like "db%";
+----------------+
| Database (db%) |
+----------------+
| db_classes |
| db_user |
+----------------+
2 rows in set (0.01 sec)
sql
mysql> use db_user;
Database changed
mysql> show tables;
+-------------------+
| Tables_in_db_user |
+-------------------+
| db_info |
+-------------------+
1 row in set (0.00 sec)
mysql> select * from db_info;
+----+------+--------+------+---------+
| id | name | gender | age | address |
+----+------+--------+------+---------+
| 1 | zs | 男 | 18 | 西安 |
| 2 | zs1 | 女 | 18 | NULL |
| 3 | zs2 | 女 | 18 | NULL |
+----+------+--------+------+---------+
3 rows in set (0.00 sec)
sql
mysql> desc db_info;
+---------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+--------------+------+-----+---------+-------+
| id | int | NO | PRI | NULL | |
| name | varchar(255) | NO | | NULL | |
| gender | char(1) | YES | | NULL | |
| age | int | YES | | 18 | |
| address | varchar(255) | YES | | NULL | |
+---------+--------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
sql
mysql> use db_classes;
Database changed
mysql> show tables;
+----------------------+
| Tables_in_db_classes |
+----------------------+
| db_hero |
+----------------------+
1 row in set (0.00 sec)
mysql> select *from db_hero;
+------+--------------+--------------+------+--------+-----------+--------------+--------------+--------+
| id | name | nickname | age | gender | address | wuqi | world | types |
+------+--------------+--------------+------+--------+-----------+--------------+--------------+--------+
| 1 | 孙悟空 | 齐天大圣 | 500 | 男 | 花果山 | 金箍棒 | 西游世界 | 妖族 |
| 2 | 猪刚鬣 | 猪八戒 | 600 | 男 | 高老庄 | 九齿钉耙 | 西游世界 | 妖族 |
| 3 | 武松 | 打虎哥 | 30 | 男 | 吴国 | 拳头 | 水浒世界 | 人族 |
| 4 | 鲁智深 | 杨柳哥 | 20 | 男 | 吴国 | 铲杖 | 水浒世界 | 人族 |
| 5 | 太白金星 | 太上老君 | 5000 | 男 | 天庭 | 毛笔 | 西游世界 | 仙族 |
+------+--------------+--------------+------+--------+-----------+--------------+--------------+--------+
5 rows in set (0.01 sec)
mysql> desc db_hero;
+----------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| id | int | YES | | NULL | |
| name | varchar(100) | YES | | NULL | |
| nickname | varchar(100) | YES | | NULL | |
| age | int | YES | | NULL | |
| gender | varchar(20) | YES | | NULL | |
| address | varchar(100) | YES | | NULL | |
| wuqi | varchar(100) | YES | | NULL | |
| world | varchar(100) | YES | | NULL | |
| types | varchar(20) | YES | | NULL | |
+----------+--------------+------+-----+---------+-------+
9 rows in set (0.00 sec)二：插入数据到数据库表中
sql
mysql> insert into db_hero values(null,"武大郎","大朗",25,"男","吴国","无","水浒世界","人族");
Query OK, 1 row affected (0.00 sec)
sql
mysql> select * from db_hero;
+------+--------------+--------------+------+--------+-----------+--------------+--------------+--------+
| id | name | nickname | age | gender | address | wuqi | world | types |
+------+--------------+--------------+------+--------+-----------+--------------+--------------+--------+
| 1 | 孙悟空 | 齐天大圣 | 500 | 男 | 花果山 | 金箍棒 | 西游世界 | 妖族 |
| 2 | 猪刚鬣 | 猪八戒 | 600 | 男 | 高老庄 | 九齿钉耙 | 西游世界 | 妖族 |
| 3 | 武松 | 打虎哥 | 30 | 男 | 吴国 | 拳头 | 水浒世界 | 人族 |
| 4 | 鲁智深 | 杨柳哥 | 20 | 男 | 吴国 | 铲杖 | 水浒世界 | 人族 |
| 5 | 太白金星 | 太上老君 | 5000 | 男 | 天庭 | 毛笔 | 西游世界 | 仙族 |
| NULL | 武大郎 | 大朗 | 25 | 男 | 吴国 | 无 | 水浒世界 | 人族 |
+------+--------------+--------------+------+--------+-----------+--------------+--------------+--------+
6 rows in set (0.00 sec)
sql
mysql> insert into db_hero values(7,"武大郎","大朗",25,"男","吴国","无","水浒世界","人族");
Query OK, 1 row affected (0.01 sec)
sql
mysql> select * from db_hero;
+------+--------------+--------------+------+--------+-----------+--------------+--------------+--------+
| id | name | nickname | age | gender | address | wuqi | world | types |
+------+--------------+--------------+------+--------+-----------+--------------+--------------+--------+
| 1 | 孙悟空 | 齐天大圣 | 500 | 男 | 花果山 | 金箍棒 | 西游世界 | 妖族 |
| 2 | 猪刚鬣 | 猪八戒 | 600 | 男 | 高老庄 | 九齿钉耙 | 西游世界 | 妖族 |
| 3 | 武松 | 打虎哥 | 30 | 男 | 吴国 | 拳头 | 水浒世界 | 人族 |
| 4 | 鲁智深 | 杨柳哥 | 20 | 男 | 吴国 | 铲杖 | 水浒世界 | 人族 |
| 5 | 太白金星 | 太上老君 | 5000 | 男 | 天庭 | 毛笔 | 西游世界 | 仙族 |
| NULL | 武大郎 | 大朗 | 25 | 男 | 吴国 | 无 | 水浒世界 | 人族 |
| 7 | 武大郎 | 大朗 | 25 | 男 | 吴国 | 无 | 水浒世界 | 人族 |
+------+--------------+--------------+------+--------+-----------+--------------+--------------+--------+
7 rows in set (0.00 sec)三：删除数据库表中的数据
sql
mysql> delete from db_hero where id=1;
Query OK, 1 row affected (0.01 sec)
sql
mysql> select * from db_hero;
+------+--------------+--------------+------+--------+-----------+--------------+--------------+--------+
| id | name | nickname | age | gender | address | wuqi | world | types |
+------+--------------+--------------+------+--------+-----------+--------------+--------------+--------+
| 2 | 猪刚鬣 | 猪八戒 | 600 | 男 | 高老庄 | 九齿钉耙 | 西游世界 | 妖族 |
| 3 | 武松 | 打虎哥 | 30 | 男 | 吴国 | 拳头 | 水浒世界 | 人族 |
| 4 | 鲁智深 | 杨柳哥 | 20 | 男 | 吴国 | 铲杖 | 水浒世界 | 人族 |
| 5 | 太白金星 | 太上老君 | 5000 | 男 | 天庭 | 毛笔 | 西游世界 | 仙族 |
| NULL | 武大郎 | 大朗 | 25 | 男 | 吴国 | 无 | 水浒世界 | 人族 |
| 7 | 武大郎 | 大朗 | 25 | 男 | 吴国 | 无 | 水浒世界 | 人族 |
| 8 | 红孩儿 | 无 | 25 | 男 | 妖界 | 无 | 西游世界 | 仙族 |
| NULL | 金角大王 | NULL | NULL | NULL | NULL | NULL | NULL | NULL |
| NULL | 银角大王 | NULL | NULL | 男 | NULL | NULL | NULL | NULL |
| NULL | 银角大王 | NULL | NULL | 男 | NULL | NULL | NULL | NULL |
| NULL | 孙尚香 | NULL | NULL | 女 | NULL | NULL | NULL | NULL |
| NULL | 马超 | NULL | NULL | 男 | NULL | NULL | NULL | NULL |
+------+--------------+--------------+------+--------+-----------+--------------+--------------+--------+
12 rows in set (0.00 sec)
sql
mysql> delete from db_hero where name="银角大王";
Query OK, 2 rows affected (0.00 sec)
sql
mysql> select * from db_hero;
+------+--------------+--------------+------+--------+-----------+--------------+--------------+--------+
| id | name | nickname | age | gender | address | wuqi | world | types |
+------+--------------+--------------+------+--------+-----------+--------------+--------------+--------+
| 2 | 猪刚鬣 | 猪八戒 | 600 | 男 | 高老庄 | 九齿钉耙 | 西游世界 | 妖族 |
| 3 | 武松 | 打虎哥 | 30 | 男 | 吴国 | 拳头 | 水浒世界 | 人族 |
| 4 | 鲁智深 | 杨柳哥 | 20 | 男 | 吴国 | 铲杖 | 水浒世界 | 人族 |
| 5 | 太白金星 | 太上老君 | 5000 | 男 | 天庭 | 毛笔 | 西游世界 | 仙族 |
| NULL | 武大郎 | 大朗 | 25 | 男 | 吴国 | 无 | 水浒世界 | 人族 |
| 7 | 武大郎 | 大朗 | 25 | 男 | 吴国 | 无 | 水浒世界 | 人族 |
| 8 | 红孩儿 | 无 | 25 | 男 | 妖界 | 无 | 西游世界 | 仙族 |
| NULL | 金角大王 | NULL | NULL | NULL | NULL | NULL | NULL | NULL |
| NULL | 孙尚香 | NULL | NULL | 女 | NULL | NULL | NULL | NULL |
| NULL | 马超 | NULL | NULL | 男 | NULL | NULL | NULL | NULL |
+------+--------------+--------------+------+--------+-----------+--------------+--------------+--------+
10 rows in set (0.00 sec)
sql
mysql> use db_user;
Database changed
mysql> show tables;
+-------------------+
| Tables_in_db_user |
+-------------------+
| db_info |
+-------------------+
1 row in set (0.00 sec)
mysql> select *from db_info;
+----+------+--------+------+---------+
| id | name | gender | age | address |
+----+------+--------+------+---------+
| 1 | zs | 男 | 18 | 西安 |
| 2 | zs1 | 女 | 18 | NULL |
| 3 | zs2 | 女 | 18 | NULL |
+----+------+--------+------+---------+
3 rows in set (0.00 sec)3.1truncate指令
该指令也可以删除数据，注意：这种数据删除不通过数据字典，是无法恢复的，请慎用！！！！
主要使用场景：清除测试数据！！！！
sql
mysql> truncate db_info;
Query OK, 0 rows affected (0.02 sec)
sql
mysql> select *from db_info;
Empty set (0.01 sec)
mysql> desc db_info;
+---------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+--------------+------+-----+---------+-------+
| id | int | NO | PRI | NULL | |
| name | varchar(255) | NO | | NULL | |
| gender | char(1) | YES | | NULL | |
| age | int | YES | | 18 | |
| address | varchar(255) | YES | | NULL | |
+---------+--------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
sql
mysql> insert into db_info values(1,"张三","男",18,"西安");
Query OK, 1 row affected (0.00 sec)
mysql> select * from db_info;
+----+--------+--------+------+---------+
| id | name | gender | age | address |
+----+--------+--------+------+---------+
| 1 | 张三 | 男 | 18 | 西安 |
+----+--------+--------+------+---------+
1 row in set (0.00 sec)
sql
mysql> insert into db_info values(2,"离李四","男",18,"西安");
Query OK, 1 row affected (0.01 sec)
mysql> insert into db_info values(三,"王五","男",18,"西安");
ERROR 1054 (42S22): Unknown column '三' in 'field list'
mysql> insert into db_info values(3,"王五","男",18,"西安");
Query OK, 1 row affected (0.01 sec)
mysql> insert into db_info values(4,"孙尚香","女",18,"西安");
Query OK, 1 row affected (0.01 sec)
mysql> insert into db_info values(5,"鲁智深","男",18,"西安");
Query OK, 1 row affected (0.01 sec)
mysql> select* from db_info;
+----+-----------+--------+------+---------+
| id | name | gender | age | address |
+----+-----------+--------+------+---------+
| 1 | 张三 | 男 | 18 | 西安 |
| 2 | 离李四 | 男 | 18 | 西安 |
| 3 | 王五 | 男 | 18 | 西安 |
| 4 | 孙尚香 | 女 | 18 | 西安 |
| 5 | 鲁智深 | 男 | 18 | 西安 |
+----+-----------+--------+------+---------+
5 rows in set (0.00 sec)四： 增加数据
4.1update指令
sql
update 表名称 set 字段名称=新的值 [,字段=xxx [,......] [where 条件];
sql
mysql> update db_info set age=44 where id=1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> update db_info set age=55 where id="2";
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from db_info;
+----+-----------+--------+------+---------+
| id | name | gender | age | address |
+----+-----------+--------+------+---------+
| 1 | 张三 | 男 | 44 | 西安 |
| 2 | 离李四 | 男 | 55 | 西安 |
| 3 | 王五 | 男 | 18 | 西安 |
| 4 | 孙尚香 | 女 | 18 | 西安 |
| 5 | 鲁智深 | 男 | 18 | 西安 |
+----+-----------+--------+------+---------+
5 rows in set (0.00 sec)
sql
mysql> update db_info set age = age+1;
Query OK, 5 rows affected (0.00 sec)
Rows matched: 5 Changed: 5 Warnings: 0
mysql> select * from db_info;
+----+-----------+--------+------+---------+
| id | name | gender | age | address |
+----+-----------+--------+------+---------+
| 1 | 张三 | 男 | 45 | 西安 |
| 2 | 离李四 | 男 | 56 | 西安 |
| 3 | 王五 | 男 | 19 | 西安 |
| 4 | 孙尚香 | 女 | 19 | 西安 |
| 5 | 鲁智深 | 男 | 19 | 西安 |
+----+-----------+--------+------+---------+
5 rows in set (0.00 sec)
mysql> update db_info set address="四川绵阳";
Query OK, 5 rows affected (0.01 sec)
Rows matched: 5 Changed: 5 Warnings: 0
mysql> select *from db_info;
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 1 | 张三 | 男 | 45 | 四川绵阳 |
| 2 | 离李四 | 男 | 56 | 四川绵阳 |
| 3 | 王五 | 男 | 19 | 四川绵阳 |
| 4 | 孙尚香 | 女 | 19 | 四川绵阳 |
| 5 | 鲁智深 | 男 | 19 | 四川绵阳 |
+----+-----------+--------+------+--------------+
5 rows in set (0.00 sec)4.2replace语句
replace语句结构和insert的语法结构一模一样
sql
replace into 表名称[(字段1 [,字段2, ......])] {values|value}(字段值, [......]) [,()];
注意：replace 的sql语句，是集更新和插入于一体的一个SQL。
如果插入的数据不存在（主键、unqiue修饰的字段），执行insert执行
如果插入的数据存在（主键、unqiue修饰的字段），则先执行删除语句，再执行insert语句。
sql
mysql> replace into db_info(id,name,gender) values(6,"曹操","男");
Query OK, 1 row affected (0.01 sec)
mysql> select *from db_info;
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 1 | 张三 | 男 | 45 | 四川绵阳 |
| 2 | 离李四 | 男 | 56 | 四川绵阳 |
| 3 | 王五 | 男 | 19 | 四川绵阳 |
| 4 | 孙尚香 | 女 | 19 | 四川绵阳 |
| 5 | 鲁智深 | 男 | 19 | 四川绵阳 |
| 6 | 曹操 | 男 | 18 | NULL |
+----+-----------+--------+------+--------------+
6 rows in set (0.00 sec)
mysql> replace into db_info(id,name,gender) values(7,"张飞","男");
Query OK, 1 row affected (0.01 sec)
mysql> select *from db_info;
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 1 | 张三 | 男 | 45 | 四川绵阳 |
| 2 | 离李四 | 男 | 56 | 四川绵阳 |
| 3 | 王五 | 男 | 19 | 四川绵阳 |
| 4 | 孙尚香 | 女 | 19 | 四川绵阳 |
| 5 | 鲁智深 | 男 | 19 | 四川绵阳 |
| 6 | 曹操 | 男 | 18 | NULL |
| 7 | 张飞 | 男 | 18 | NULL |
+----+-----------+--------+------+--------------+
7 rows in set (0.00 sec)五：查询语句（select）
使用select查询数据库表中的某些数据。
select 语法结构
sql
select {字段|函数|其他} from 表名称 [where]
sql
mysql> select 56;
+----+
| 56 |
+----+
| 56 |
+----+
1 row in set (0.00 sec)
mysql> select 56+45;
+-------+
| 56+45 |
+-------+
| 101 |
+-------+
1 row in set (0.00 sec)
mysql> select 56*45;
+-------+
| 56*45 |
+-------+
| 2520 |
+-------+
1 row in set (0.01 sec)
mysql> select 56-45;
+-------+
| 56-45 |
+-------+
| 11 |
+-------+
1 row in set (0.01 sec)
mysql> select 56%45;
+-------+
| 56%45 |
+-------+
| 11 |
+-------+
1 row in set (0.00 sec)
mysql> select 100+"张三";
+--------------+
| 100+"张三" |
+--------------+
| 100 |
+--------------+
1 row in set, 1 warning (0.01 sec)
mysql> select "100"+200
-> ;
+-----------+
| "100"+200 |
+-----------+
| 300 |
+-----------+
1 row in set (0.00 sec)
mysql> select 100+"200张三";
+-----------------+
| 100+"200张三" |
+-----------------+
| 300 |
+-----------------+
1 row in set, 1 warning (0.00 sec)
mysql> select 100+"张三100";
+-----------------+
| 100+"张三100" |
+-----------------+
| 100 |
+-----------------+
1 row in set, 1 warning (0.00 sec)
sql
+----------+
| null + 1 |
+----------+
| NULL |
+----------+
1 row in set (0.01 sec)
mysql> select user();
+----------------+
| user() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)
mysql> select database();
+------------+
| database() |
+------------+
| db_user |
+------------+
1 row in set (0.00 sec)
mysql> select uuid();
+--------------------------------------+
| uuid() |
+--------------------------------------+
| ce2e757d-11de-11ef-8f71-0a0027000012 |
+--------------------------------------+
1 row in set (0.02 sec)
mysql> select uuid();
+--------------------------------------+
| uuid() |
+--------------------------------------+
| e4f66188-11de-11ef-8f71-0a0027000012 |
+--------------------------------------+
1 row in set (0.00 sec)
sql
mysql> select * from db_info;
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 1 | 张三 | 男 | 45 | 四川绵阳 |
| 2 | 离李四 | 男 | 56 | 四川绵阳 |
| 3 | 王五 | 男 | 19 | 四川绵阳 |
| 4 | 孙尚香 | 女 | 19 | 四川绵阳 |
| 5 | 鲁智深 | 男 | 19 | 四川绵阳 |
| 6 | 曹操 | 男 | 18 | NULL |
| 7 | 张飞 | 男 | 18 | NULL |
+----+-----------+--------+------+--------------+
7 rows in set (0.00 sec)
mysql> select id,name from db_info;
+----+-----------+
| id | name |
+----+-----------+
| 1 | 张三 |
| 2 | 离李四 |
| 3 | 王五 |
| 4 | 孙尚香 |
| 5 | 鲁智深 |
| 6 | 曹操 |
| 7 | 张飞 |
+----+-----------+
7 rows in set (0.00 sec)
mysql> select id from db_info;
+----+
| id |
+----+
| 1 |
| 2 |
| 3 |
| 4 |
| 5 |
| 6 |
| 7 |
+----+
7 rows in set (0.00 sec)5.1查询当前时间
sql
mysql> select now();
+---------------------+
| now() |
+---------------------+
| 2024-05-15 16:14:39 |
+---------------------+
1 row in set (0.00 sec)5.2模糊查询（like）
sql
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| db_classes |
| db_user |
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
6 rows in set (0.00 sec)5.2.1查询以db_开头的数据库
sql
mysql> show databases like 'db_%';
+-----------------+
| Database (db_%) |
+-----------------+
| db_classes |
| db_user |
+-----------------+
2 rows in set (0.00 sec)5.2.2查询数据库表中以张开头的信息
sql
mysql> select * from db_info where name like "张%";
+----+--------+--------+------+--------------+
| id | name | gender | age | address |
+----+--------+--------+------+--------------+
| 1 | 张三 | 男 | 45 | 四川绵阳 |
| 7 | 张飞 | 男 | 18 | NULL |
+----+--------+--------+------+--------------+
2 rows in set (0.01 sec)5.2.3查询数据库表中以香结尾的信息
sql
mysql> select * from db_info where name like "%香";
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 4 | 孙尚香 | 女 | 19 | 四川绵阳 |
+----+-----------+--------+------+--------------+
1 row in set (0.00 sec)5.2.4查询数据库表中含有"香"的信息
sql
mysql> select * from db_info where name like "%香%";
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 4 | 孙尚香 | 女 | 19 | 四川绵阳 |
+----+-----------+--------+------+--------------+
1 row in set (0.00 sec)
mysql> select * from db_info where name like "%尚%";
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 4 | 孙尚香 | 女 | 19 | 四川绵阳 |
+----+-----------+--------+------+--------------+
1 row in set (0.00 sec)
mysql> select * from db_info where name like "%张%";
+----+--------+--------+------+--------------+
| id | name | gender | age | address |
+----+--------+--------+------+--------------+
| 1 | 张三 | 男 | 45 | 四川绵阳 |
| 7 | 张飞 | 男 | 18 | NULL |
+----+--------+--------+------+--------------+
2 rows in set (0.00 sec)
mysql> insert into db_info(id,name) values(8,"秀秀");
Query OK, 1 row affected (0.00 sec)
mysql> select * from db_info;
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 1 | 张三 | 男 | 45 | 四川绵阳 |
| 2 | 离李四 | 男 | 56 | 四川绵阳 |
| 3 | 王五 | 男 | 19 | 四川绵阳 |
| 4 | 孙尚香 | 女 | 19 | 四川绵阳 |
| 5 | 鲁智深 | 男 | 19 | 四川绵阳 |
| 6 | 曹操 | 男 | 18 | NULL |
| 7 | 张飞 | 男 | 18 | NULL |
| 8 | 秀秀 | NULL | 18 | NULL |
+----+-----------+--------+------+--------------+
8 rows in set (0.00 sec)5.3查询名字第二个字为"秀"的信息
sql
mysql> select * from db_info where name like "_秀%";
+----+--------+--------+------+---------+
| id | name | gender | age | address |
+----+--------+--------+------+---------+
| 8 | 秀秀 | NULL | 18 | NULL |
+----+--------+--------+------+---------+
1 row in set (0.00 sec)5.4查询以张开头的信息
sql
mysql> select * from db_info where name like "_秀%";
+----+--------+--------+------+---------+
| id | name | gender | age | address |
+----+--------+--------+------+---------+
| 8 | 秀秀 | NULL | 18 | NULL |
+----+--------+--------+------+---------+
1 row in set (0.00 sec)5.5查询以深结尾的信息
sql
mysql> select * from db_info where name regexp "深$";
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 5 | 鲁智深 | 男 | 19 | 四川绵阳 |
+----+-----------+--------+------+--------------+
1 row in set (0.00 sec)
sql
mysql> select gender from db_info;
+--------+
| gender |
+--------+
| 男 |
| 男 |
| 男 |
| 女 |
| 男 |
| 男 |
| 男 |
| NULL |
+--------+
8 rows in set (0.00 sec)
mysql> select distinct gender from db_info;
+--------+
| gender |
+--------+
| 男 |
| 女 |
| NULL |
+--------+
3 rows in set (0.01 sec)
mysql> select gender from db_info group by gender;
+--------+
| gender |
+--------+
| 男 |
| 女 |
| NULL |
+--------+
3 rows in set (0.00 sec)六：聚会函数-count
统计数据
sql
select count(id) from user;
select count(gender) from user;
select count(id) from user;
select count(1) from user;
select count(1) from user where gender="男";
sql
mysql> use db_user;
Database changed
mysql> select * from db_info;
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 1 | 张三 | 男 | 45 | 四川绵阳 |
| 2 | 离李四 | 男 | 56 | 四川绵阳 |
| 3 | 王五 | 男 | 19 | 四川绵阳 |
| 4 | 孙尚香 | 女 | 19 | 四川绵阳 |
| 5 | 鲁智深 | 男 | 19 | 四川绵阳 |
| 6 | 曹操 | 男 | 18 | NULL |
| 7 | 张飞 | 男 | 18 | NULL |
| 8 | 秀秀 | NULL | 18 | NULL |
+----+-----------+--------+------+--------------+
8 rows in set (0.00 sec)
mysql> select count(*) from db_info;
+----------+
| count(*) |
+----------+
| 8 |
+----------+
1 row in set (0.01 sec)
mysql> select count(gender) from db_info;
+---------------+
| count(gender) |
+---------------+
| 7 |
+---------------+
1 row in set (0.00 sec)
mysql> select count(id) from db_info;
+-----------+
| count(id) |
+-----------+
| 8 |
+-----------+
1 row in set (0.00 sec)
mysql> select count(1) from db_info;
+----------+
| count(1) |
+----------+
| 8 |
+----------+
1 row in set (0.00 sec)
mysql> select count(1) from db_info where gender="男";
+----------+
| count(1) |
+----------+
| 6 |
+----------+
1 row in set (0.01 sec)
mysql> select count(1) from db_info where gender="女";
+----------+
| count(1) |
+----------+
| 1 |
+----------+
1 row in set (0.00 sec)
mysql> select count(gender),gender from db_info group by gender;
+---------------+--------+
| count(gender) | gender |
+---------------+--------+
| 6 | 男 |
| 1 | 女 |
| 0 | NULL |
+---------------+--------+
3 rows in set (0.00 sec)
mysql> select gender,count(gender) from db_info group by gender having count(gender) > 4;
+--------+---------------+
| gender | count(gender) |
+--------+---------------+
| 男 | 6 |
+--------+---------------+
1 row in set (0.00 sec)
mysql> select name from db_info;
+-----------+
| name |
+-----------+
| 张三 |
| 离李四 |
| 王五 |
| 孙尚香 |
| 鲁智深 |
| 曹操 |
| 张飞 |
| 秀秀 |
+-----------+
8 rows in set (0.00 sec)
mysql> select * from db_info order by id;
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 1 | 张三 | 男 | 45 | 四川绵阳 |
| 2 | 离李四 | 男 | 56 | 四川绵阳 |
| 3 | 王五 | 男 | 19 | 四川绵阳 |
| 4 | 孙尚香 | 女 | 19 | 四川绵阳 |
| 5 | 鲁智深 | 男 | 19 | 四川绵阳 |
| 6 | 曹操 | 男 | 18 | NULL |
| 7 | 张飞 | 男 | 18 | NULL |
| 8 | 秀秀 | NULL | 18 | NULL |
+----+-----------+--------+------+--------------+
8 rows in set (0.00 sec)七：排序 order by 字段 [{asc | desc }]
如果存在排序，必须是在分组之后
sql
select 字段
from 表名
[where 条件]
[group by 字段 [, 字段 [,......]] ]
[having 筛选条件]
order by 字段 [{asc | desc }] [, 字段 [{asc | desc }]]
案例
select * from user order by age ;
select * from user order by age desc;
select * from user order by age asc;
select * from user order by age , id desc;
sql
年龄排序
mysql> select * from db_info order by age;
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 6 | 曹操 | 男 | 18 | NULL |
| 7 | 张飞 | 男 | 18 | NULL |
| 8 | 秀秀 | NULL | 18 | NULL |
| 3 | 王五 | 男 | 19 | 四川绵阳 |
| 4 | 孙尚香 | 女 | 19 | 四川绵阳 |
| 5 | 鲁智深 | 男 | 19 | 四川绵阳 |
| 1 | 张三 | 男 | 45 | 四川绵阳 |
| 2 | 离李四 | 男 | 56 | 四川绵阳 |
+----+-----------+--------+------+--------------+
8 rows in set (0.00 sec)
年龄升序
mysql> select * from db_info order by age, id desc;
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 8 | 秀秀 | NULL | 18 | NULL |
| 7 | 张飞 | 男 | 18 | NULL |
| 6 | 曹操 | 男 | 18 | NULL |
| 5 | 鲁智深 | 男 | 19 | 四川绵阳 |
| 4 | 孙尚香 | 女 | 19 | 四川绵阳 |
| 3 | 王五 | 男 | 19 | 四川绵阳 |
| 1 | 张三 | 男 | 45 | 四川绵阳 |
| 2 | 离李四 | 男 | 56 | 四川绵阳 |
+----+-----------+--------+------+--------------+
8 rows in set (0.00 sec)
mysql> select * from db_info where id>0 group by id order by age, id desc;
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 8 | 秀秀 | NULL | 18 | NULL |
| 7 | 张飞 | 男 | 18 | NULL |
| 6 | 曹操 | 男 | 18 | NULL |
| 5 | 鲁智深 | 男 | 19 | 四川绵阳 |
| 4 | 孙尚香 | 女 | 19 | 四川绵阳 |
| 3 | 王五 | 男 | 19 | 四川绵阳 |
| 1 | 张三 | 男 | 45 | 四川绵阳 |
| 2 | 离李四 | 男 | 56 | 四川绵阳 |
+----+-----------+--------+------+--------------+
8 rows in set (0.01 sec)
mysql> select * from db_info where id>0 group by id having count(id) = 1 order by age, id desc;
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 8 | 秀秀 | NULL | 18 | NULL |
| 7 | 张飞 | 男 | 18 | NULL |
| 6 | 曹操 | 男 | 18 | NULL |
| 5 | 鲁智深 | 男 | 19 | 四川绵阳 |
| 4 | 孙尚香 | 女 | 19 | 四川绵阳 |
| 3 | 王五 | 男 | 19 | 四川绵阳 |
| 1 | 张三 | 男 | 45 | 四川绵阳 |
| 2 | 离李四 | 男 | 56 | 四川绵阳 |
+----+-----------+--------+------+--------------+
8 rows in set (0.00 sec)
mysql> sclect count(*) from db_info;八：别名的使用
别名（alias ），就是将原有名称，重新赋予一个新的名称
在查询SQL时，可以将查询的结果重新设置名称（字段、表名称）。
sql
字段 as 别名 ，as可以省略
select count(*) as count from user;
select count(*) count from user;
sql
mysql> select count(*) as count from db_info;
+-------+
| count |
+-------+
| 8 |
+-------+
1 row in set (0.00 sec)
mysql> select count(*) count from db_info;
+-------+
| count |
+-------+
| 8 |
+-------+
1 row in set (0.00 sec)
sql
mysql> select id, name, age from db_info where id<6;
+----+-----------+------+
| id | name | age |
+----+-----------+------+
| 1 | 张三 | 45 |
| 2 | 离李四 | 56 |
| 3 | 王五 | 19 |
| 4 | 孙尚香 | 19 |
| 5 | 鲁智深 | 19 |
+----+-----------+------+
5 rows in set (0.00 sec)
mysql> select * from (select id, name, age from db_info where id<6) as t where t.id = 1;
+----+--------+------+
| id | name | age |
+----+--------+------+
| 1 | 张三 | 45 |
+----+--------+------+
1 row in set (0.01 sec)九：分页查询
查询非常多，此时全部展示是不现实的，因此，需要通过分页展示部分数据
注意：不同的关系型数据库，实现分页效果，可能SQL不一样！！！
MySQL使用 limit关键字实现分页！！！
sql
mysql> select * from db_info limit 3;
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 1 | 张三 | 男 | 45 | 四川绵阳 |
| 2 | 离李四 | 男 | 56 | 四川绵阳 |
| 3 | 王五 | 男 | 19 | 四川绵阳 |
+----+-----------+--------+------+--------------+
3 rows in set (0.00 sec)
mysql> select * from db_info limit 5;
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 1 | 张三 | 男 | 45 | 四川绵阳 |
| 2 | 离李四 | 男 | 56 | 四川绵阳 |
| 3 | 王五 | 男 | 19 | 四川绵阳 |
| 4 | 孙尚香 | 女 | 19 | 四川绵阳 |
| 5 | 鲁智深 | 男 | 19 | 四川绵阳 |
+----+-----------+--------+------+--------------+
5 rows in set (0.00 sec)
mysql> select * from db_info limit 0,5;
+----+-----------+--------+------+--------------+
| id | name | gender | age | address |
+----+-----------+--------+------+--------------+
| 1 | 张三 | 男 | 45 | 四川绵阳 |
| 2 | 离李四 | 男 | 56 | 四川绵阳 |
| 3 | 王五 | 男 | 19 | 四川绵阳 |
| 4 | 孙尚香 | 女 | 19 | 四川绵阳 |
| 5 | 鲁智深 | 男 | 19 | 四川绵阳 |
+----+-----------+--------+------+--------------+
5 rows in set (0.00 sec)
mysql> select * from db_info limit 5,5;
+----+--------+--------+------+---------+
| id | name | gender | age | address |
+----+--------+--------+------+---------+
| 6 | 曹操 | 男 | 18 | NULL |
| 7 | 张飞 | 男 | 18 | NULL |
| 8 | 秀秀 | NULL | 18 | NULL |
+----+--------+--------+------+---------+
3 rows in set (0.00 sec)
sql
C:\Users\GUOGUO>mysql --help
mysql Ver 8.1.0 for Win64 on x86_64 (MySQL Community Server - GPL)
Copyright (c) 2000, 2023, Oracle and/or its affiliates.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Usage: mysql [OPTIONS] [database]
-?, --help Display this help and exit.
-I, --help Synonym for -?
--auto-rehash Enable automatic rehashing. One doesn't need to use
'rehash' to get table and field completion, but startup
and reconnecting may take a longer time. Disable with
--disable-auto-rehash.
(Defaults to on; use --skip-auto-rehash to disable.)
-A, --no-auto-rehash
No automatic rehashing. One has to use 'rehash' to get
table and field completion. This gives a quicker start of
mysql and disables rehashing on reconnect.
--auto-vertical-output
Automatically switch to vertical output mode if the
result is wider than the terminal width.
-B, --batch Don't use history file. Disable interactive behavior.
(Enables --silent.)
--bind-address=name IP address to bind to.
--binary-as-hex Print binary data as hex. Enabled by default for
interactive terminals.
--character-sets-dir=name
Directory for character set files.
--column-type-info Display column type information.
-c, --comments Preserve comments. Send comments to the server. The
default is --comments (keep comments), disable with
--skip-comments.
(Defaults to on; use --skip-comments to disable.)
-C, --compress Use compression in server/client protocol.
-#, --debug[=#] This is a non-debug version. Catch this and exit.
--debug-check This is a non-debug version. Catch this and exit.
-T, --debug-info This is a non-debug version. Catch this and exit.
-D, --database=name Database to use.
--default-character-set=name
Set the default character set.
--delimiter=name Delimiter to be used.
--enable-cleartext-plugin
Enable/disable the clear text authentication plugin.
-e, --execute=name Execute command and quit. (Disables --force and history
file.)
-E, --vertical Print the output of a query (rows) vertically.
-f, --force Continue even if we get an SQL error.
--histignore=name A colon-separated list of patterns to keep statements
from getting logged into syslog and mysql history.
-G, --named-commands
Enable named commands. Named commands mean this program's
internal commands; see mysql> help . When enabled, the
named commands can be used from any line of the query,
otherwise only from the first line, before an enter.
Disable with --disable-named-commands. This option is
disabled by default.
-i, --ignore-spaces Ignore space after function names.
--init-command=name SQL Command to execute when connecting to MySQL server.
Will automatically be re-executed when reconnecting.
--local-infile Enable/disable LOAD DATA LOCAL INFILE.
-b, --no-beep Turn off beep on error.
-h, --host=name Connect to host.
--dns-srv-name=name Connect to a DNS SRV resource
-H, --html Produce HTML output.
-X, --xml Produce XML output.
--line-numbers Write line numbers for errors.
(Defaults to on; use --skip-line-numbers to disable.)
-L, --skip-line-numbers
Don't write line number for errors.
-n, --unbuffered Flush buffer after each query.
--column-names Write column names in results.
(Defaults to on; use --skip-column-names to disable.)
-N, --skip-column-names
Don't write column names in results.
--sigint-ignore Ignore SIGINT (CTRL-C).
-o, --one-database Ignore statements except those that occur while the
default database is the one named at the command line.
-p, --password[=name]
Password to use when connecting to server. If password is
not given it's asked from the tty.
-,, --password1[=name]
Password for first factor authentication plugin.
-,, --password2[=name]
Password for second factor authentication plugin.
-,, --password3[=name]
Password for third factor authentication plugin.
-W, --pipe Use named pipes to connect to server.
-P, --port=# Port number to use for connection or 0 for default to, in
order of preference, my.cnf, $MYSQL_TCP_PORT,
/etc/services, built-in default (3306).
--prompt=name Set the mysql prompt to this value.
--protocol=name The protocol to use for connection (tcp, socket, pipe,
memory).
-q, --quick Don't cache result, print it row by row. This may slow
down the server if the output is suspended. Doesn't use
history file.
-r, --raw Write fields without conversion. Used with --batch.
--reconnect Reconnect if the connection is lost. Disable with
--disable-reconnect. This option is enabled by default.
(Defaults to on; use --skip-reconnect to disable.)
-s, --silent Be more silent. Print results with a tab as separator,
each row on new line.
--shared-memory-base-name=name
Base name of shared memory.
-S, --socket=name The socket file to use for connection.
--server-public-key-path=name
File path to the server public RSA key in PEM format.
--get-server-public-key
Get server public key
--ssl-mode=name SSL connection mode.
--ssl-ca=name CA file in PEM format.
--ssl-capath=name CA directory.
--ssl-cert=name X509 cert in PEM format.
--ssl-cipher=name SSL cipher to use.
--ssl-key=name X509 key in PEM format.
--ssl-crl=name Certificate revocation list.
--ssl-crlpath=name Certificate revocation list path.
--tls-version=name TLS version to use, permitted values are: TLSv1.2,
TLSv1.3
--ssl-fips-mode=name
SSL FIPS mode (applies only for OpenSSL); permitted
values are: OFF, ON, STRICT
--tls-ciphersuites=name
TLS v1.3 cipher to use.
--ssl-session-data=name
Session data file to use to enable ssl session reuse
--ssl-session-data-continue-on-failed-reuse
If set to ON, this option will allow connection to
succeed even if session data cannot be reused.
--tls-sni-servername=name
The SNI server name to pass to server
-t, --table Output in table format.
--tee=name Append everything into outfile. See interactive help (\h)
also. Does not work in batch mode. Disable with
--disable-tee. This option is disabled by default.
-u, --user=name User for login if not current user.
-U, --safe-updates Only allow UPDATE and DELETE that uses keys.
-U, --i-am-a-dummy Synonym for option --safe-updates, -U.
-v, --verbose Write more. (-v -v -v gives the table output format).
-V, --version Output version information and exit.
-w, --wait Wait and retry if connection is down.
--connect-timeout=# Number of seconds before connection timeout.
--max-allowed-packet=#
The maximum packet length to send to or receive from
server.
--net-buffer-length=#
The buffer size for TCP/IP and socket communication.
--select-limit=# Automatic limit for SELECT when using --safe-updates.
--max-join-size=# Automatic limit for rows in a join when using
--safe-updates.
--show-warnings Show warnings after every statement.
-j, --syslog Log filtered interactive commands to syslog. Filtering of
commands depends on the patterns supplied via histignore
option besides the default patterns.
--plugin-dir=name Directory for client-side plugins.
--default-auth=name Default authentication client-side plugin to use.
--binary-mode By default, ASCII '\0' is disallowed and '\r\n' is
translated to '\n'. This switch turns off both features,
and also turns off parsing of all clientcommands except
\C and DELIMITER, in non-interactive mode (for input
piped to mysql or loaded using the 'source' command).
This is necessary when processing output from mysqlbinlog
that may contain blobs.
--connect-expired-password
Notify the server that this client is prepared to handle
expired password sandbox mode.
--compression-algorithms=name
Use compression algorithm in server/client protocol.
Valid values are any combination of
'zstd','zlib','uncompressed'.
--zstd-compression-level=#
Use this compression level in the client/server protocol,
in case --compression-algorithms=zstd. Valid range is
between 1 and 22, inclusive. Default is 3.
--load-data-local-dir=name
Directory path safe for LOAD DATA LOCAL INFILE to read
from.
--fido-register-factor=name
Specifies authentication factor, for which registration
needs to be done.
--authentication-oci-client-config-profile=name
Specifies the configuration profile whose configuration
options are to be read from the OCI configuration file.
Default is DEFAULT.
--oci-config-file=name
Specifies the location of the OCI configuration file.
Default for Linux is ~/.oci/config and %HOME/.oci/config
on Windows.
--telemetry-client Load the telemetry_client plugin.
--plugin-authentication-kerberos-client-mode=name
Kerberos authentication mode. Valid values: SSPI, GSSAPI.
If not specified, default is SSPI
Default options are read from the following files in the given order:
C:\WINDOWS\my.ini C:\WINDOWS\my.cnf C:\my.ini C:\my.cnf D:\mysql8.1.0\mysql-8.1.0-winx64\mysql-8.1.0-winx64\my.ini D:\mysql8.1.0\mysql-8.1.0-winx64\mysql-8.1.0-winx64\my.cnf
The following groups are read: mysql client
The following options may be given as the first argument:
--print-defaults Print the program argument list and exit.
--no-defaults Don't read default options from any option file,
except for login file.
--defaults-file=# Only read default options from the given file #.
--defaults-extra-file=# Read this file after the global files are read.
--defaults-group-suffix=#
Also read groups with concat(group, suffix)
--login-path=# Read this path from the login file.
Variables (--variable-name=value)
and boolean options {FALSE|TRUE} Value (after reading options)
------------------------------------------ -------------------------------
auto-rehash TRUE
auto-vertical-output FALSE
bind-address (No default value)
binary-as-hex FALSE
character-sets-dir (No default value)
column-type-info FALSE
comments TRUE
compress FALSE
database (No default value)
default-character-set utf8mb4
delimiter ;
enable-cleartext-plugin FALSE
vertical FALSE
force FALSE
histignore (No default value)
named-commands FALSE
ignore-spaces FALSE
init-command (No default value)
local-infile FALSE
no-beep FALSE
host (No default value)
dns-srv-name (No default value)
html FALSE
xml FALSE
line-numbers TRUE
unbuffered FALSE
column-names TRUE
sigint-ignore FALSE
port 3306
prompt mysql>
quick FALSE
raw FALSE
reconnect TRUE
shared-memory-base-name (No default value)
socket (No default value)
server-public-key-path (No default value)
get-server-public-key FALSE
ssl-ca (No default value)
ssl-capath (No default value)
ssl-cert (No default value)
ssl-cipher (No default value)
ssl-key (No default value)
ssl-crl (No default value)
ssl-crlpath (No default value)
tls-version (No default value)
tls-ciphersuites (No default value)
ssl-session-data (No default value)
ssl-session-data-continue-on-failed-reuse FALSE
tls-sni-servername (No default value)
table FALSE
user (No default value)
safe-updates FALSE
i-am-a-dummy FALSE
connect-timeout 0
max-allowed-packet 16777216
net-buffer-length 16384
select-limit 1000
max-join-size 1000000
show-warnings FALSE
plugin-dir (No default value)
default-auth (No default value)
binary-mode FALSE
connect-expired-password FALSE
compression-algorithms (No default value)
zstd-compression-level 3
load-data-local-dir (No default value)
fido-register-factor (No default value)
authentication-oci-client-config-profile (No default value)
oci-config-file (No default value)
telemetry-client FALSE
C:\Users\GUOGUO>
C:\Users\GUOGUO>
C:\Users\GUOGUO>
C:\Users\GUOGUO>mysql -uroot -p123456;
mysql: [Warning] Using a password on the command line interface can be insecure.
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
C:\Users\GUOGUO>mysql -uroot -p123456
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 13
Server version: 8.1.0 MySQL Community Server - GPL
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