Msql学习-例子

所需要用到的创建表格的代码如下：

create table dept
(
deptno numeric(2),
dname varchar(14),
loc varchar(13),
constraint pk_dept primary key(deptno)
);
create table emp
(
empno numeric(4),
ename varchar(10),
job varchar(9),
mgr numeric(4),
hiredate date,
sal numeric(7,2),
comm numeric(7,2),
deptno numeric(2),
constraint pk_emp primary key(empno),
constraint fk_deptno foreign key(deptno) references dept(deptno)
);
insert into dept values(10,'ACCOUNTING','NEW YORK');
insert into dept values (20,'RESEARCH','DALLAS');
insert into dept values (30,'SALES','CHICAGO');
insert into dept values (40,'OPERATIONS','BOSTON');
insert into emp values(7369,'SMITH','CLERK',7902,'1980-12-17',800,NULL,20);
insert into emp values (7499,'ALLEN','SALESMAN',7698,'1981-02-02',1600,300,30);
insert into emp values (7521,'WARD','SALESMAN',7698,'1981-02-22',1250,500,30);
insert into emp values (7566,'JONES','MANAGER',7839,'1981-04-02',2975,NULL,20);
insert into emp values (7654,'MARTIN','SALESMAN',7698,'1981-09-28',1250,1400,30);
insert into emp values (7698,'BLAKE','MANAGER',7839,'1981-05-01',2850,NULL,30);
insert into emp values (7782,'CLARK','MANAGER',7839,'1981-06-09',2450,NULL,10);
insert into emp
values (7839,'KING','PRESIDENT',NULL,'1981-11-17',5000,NULL,10);
insert into emp values (7844,'TURNER','SALESMAN',7698,'1981-09-08',1500,0,30);
insert into emp values (7900,'JAMES','CLERK',7698,'1981-12-03',950,NULL,30);
insert into emp values (7902,'FORD','ANALYST',7566,'1981-12-03',3000,NULL,20);
insert into emp values (7934,'MILLER','CLERK',7782,'1982-01-23',1300,NULL,10);

表视图：

emp表结构

emp表视图

dept表结构

dept表视图

Mysql简单select句子

列出管理MySQL数据库服务的常用命令：
Systemctl start/stop/status/restart mysql

#用root用户连接数据库，查询当前有哪些数据库
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

#创建db数据库，执行scott.sql脚本文件，创建测试表emp和dept
mysql> create database db;
Query OK, 1 row affected (0.07 sec)
mysql> use db
Database changed
mysql> source scott.sql

#连接db数据库，查询db数据库中有哪些表
mysql> show tables;
+--------------+
| Tables_in_db |
+--------------+
| dept         |
| emp          |
+--------------+
2 rows in set (0.00 sec)

#查看emp和dept表的结构。
mysql> desc dept;（查询表dept结构）
+--------+--------------+------+-----+---------+-------+
| Field  | Type         | Null | Key | Default | Extra |
+--------+--------------+------+-----+---------+-------+
| deptno | decimal(2,0) | NO   | PRI | NULL    |       |
| dname  | varchar(14)  | YES  |     | NULL    |       |
| loc    | varchar(13)  | YES  |     | NULL    |       |
+--------+--------------+------+-----+---------+-------+
3 rows in set (0.01 sec)
mysql> desc emp;（查询表emp结构）
+----------+--------------+------+-----+---------+-------+
| Field    | Type         | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| empno    | decimal(4,0) | NO   | PRI | NULL    |       |
| ename    | varchar(10)  | YES  |     | NULL    |       |
| job      | varchar(9)   | YES  |     | NULL    |       |
| mgr      | decimal(4,0) | YES  |     | NULL    |       |
| hiredate | datetime     | YES  |     | NULL    |       |
| sal      | decimal(7,2) | YES  |     | NULL    |       |
| comm     | decimal(7,2) | YES  |     | NULL    |       |
| deptno   | decimal(2,0) | YES  | MUL | NULL    |       |
+----------+--------------+------+-----+---------+-------+
8 rows in set (0.00 sec)

#连接db数据库，查询emp表中的所有人的姓名。
mysql> select ename from emp;
+--------+
| ename  |
+--------+
| SMITH  |
| ALLEN  |
| WARD   |
| JONES  |
| MARTIN |
| BLAKE  |
| CLARK  |
| KING   |
| TURNER |
| JAMES  |
| FORD   |
| MILLER |
+--------+
12 rows in set (0.00 sec)

#用别名把上面查询结果中的列名ename改为汉字：员工名称。
mysql> select ename as 员工名称；
     -> from emp;
+-----------------+
| 员工名称；      |
+-----------------+
| SMITH           |
| ALLEN           |
| WARD            |
| JONES           |
| MARTIN          |
| BLAKE           |
| CLARK           |
| KING            |
| TURNER          |
| JAMES           |
| FORD            |
| MILLER          |
+-----------------+
12 rows in set (0.00 sec)

#查询emp表中的不重复的部门号。
mysql> select distinct deptno from emp;
+--------+
| deptno |
+--------+
|     10 |
|     20 |
|     30 |
+--------+
3 rows in set (0.00 sec)

#查询emp表中，工资额大于2000的员工的姓名及其工资额。
mysql> select ename,sal from emp where sal > 2000;
+-------+---------+
| ename | sal     |
+-------+---------+
| JONES | 2975.00 |
| BLAKE | 2850.00 |
| CLARK | 2450.00 |
| KING  | 5000.00 |
| FORD  | 3000.00 |
+-------+---------+

#查询emp表中，工资额界于2000与3000之间的员工姓名及其工资额。
方法一：
mysql> select ename,sal from emp where sal >= 2000 and sal <= 3000;
+-------+---------+
| ename | sal     |
+-------+---------+
| JONES | 2975.00 |
| BLAKE | 2850.00 |
| CLARK | 2450.00 |
| FORD  | 3000.00 |
+-------+---------+
4 rows in set (0.00 sec)
方法二：
mysql> select ename,sal from emp where sal between 2000 and 3000;
+-------+---------+
| ename | sal     |
+-------+---------+
| JONES | 2975.00 |
| BLAKE | 2850.00 |
| CLARK | 2450.00 |
| FORD  | 3000.00 |
+-------+---------+
4 rows in set (0.00 sec)

#查询emp表中，ename列以字母A开头的员工的姓名。
mysql> select ename,sal from emp where ename like 'A%';
+-------+---------+
| ename | sal     |
+-------+---------+
| ALLEN | 1600.00 |
+-------+---------+
1 row in set (0.00 sec)

#查询emp表中，ename列含有字母A的员工的姓名。
   mysql> select ename,sal from emp where ename like '%A%';
+--------+---------+
| ename  | sal     |
+--------+---------+
| ALLEN  | 1600.00 |
| WARD   | 1250.00 |
| MARTIN | 1250.00 |
| BLAKE  | 2850.00 |
| CLARK  | 2450.00 |
| JAMES  |  950.00 |
+--------+---------+
6 rows in set (0.00 sec)

#查询emp表中，ename列第三个字母为A、第五个字母为R的员工的姓名。
mysql> select ename,sal from emp where ename like '__A_R%';
Empty set (0.00 sec)

#查询emp表中，姓名及工资额，要求工资按照降序排序。
mysql> select ename,sal(从低到高)
-> from emp
-> order by sal;
+--------+---------+
| ename  | sal     |
+--------+---------+
| SMITH  |  800.00 |
| JAMES  |  950.00 |
| WARD   | 1250.00 |
| MARTIN | 1250.00 |
| MILLER | 1300.00 |
| TURNER | 1500.00 |
| ALLEN  | 1600.00 |
| CLARK  | 2450.00 |
| BLAKE  | 2850.00 |
| JONES  | 2975.00 |
| FORD   | 3000.00 |
| KING   | 5000.00 |
+--------+---------+
12 rows in set (0.00 sec)
mysql> select ename,sal from emp order by sal desc;（丛高到低）
+--------+---------+
| ename  | sal     |
+--------+---------+
| KING   | 5000.00 |
| FORD   | 3000.00 |
| JONES  | 2975.00 |
| BLAKE  | 2850.00 |
| CLARK  | 2450.00 |
| ALLEN  | 1600.00 |
| TURNER | 1500.00 |
| MILLER | 1300.00 |
| WARD   | 1250.00 |
| MARTIN | 1250.00 |
| JAMES  |  950.00 |
| SMITH  |  800.00 |
+--------+---------+
12 rows in set (0.00 sec)

#查询emp表中，comm列为NULL的员工的姓名。
mysql> select ename from emp where comm is null;
+--------+
| ename  |
+--------+
| SMITH  |
| JONES  |
| BLAKE  |
| CLARK  |
| KING   |
| JAMES  |
| FORD   |
| MILLER |
+--------+
8 rows in set (0.00 sec)

mysql> select ename from emp where comm is not null;
+--------+
| ename  |
+--------+
| ALLEN  |
| WARD   |
| MARTIN |
| TURNER |
+--------+
4 rows in set (0.00 sec)

汇总函数

#查询每个部门的最高工资，要求列出部门编号及其最高工资额。
mysql> select deptno,max(sal) from emp group by deptno;
+--------+----------+
| deptno | max(sal) |
+--------+----------+
|     10 |  5000.00 |
|     20 |  3000.00 |
|     30 |  2850.00 |
+--------+----------+
3 rows in set (0.00 sec)

#查询各个工种的人数。
mysql> select job 工种,count(empno) 员工人数 from emp group by job;
+-----------+--------------+
| 工种      | 员工人数     |
+-----------+--------------+
| CLERK     |            3 |
| SALESMAN  |            4 |
| MANAGER   |            3 |
| PRESIDENT |            1 |
| ANALYST   |            1 |
+-----------+--------------+
5 rows in set (0.00 sec)

#查询sal列上有无重复值，给出判断语句及判断结果。
方法一：
mysql> select sal,count(sal) from emp group by sal having count(sal);
+---------+------------+
| sal     | count(sal) |
+---------+------------+
|  800.00 |          1 |
| 1600.00 |          1 |
| 1250.00 |          2 |
| 2975.00 |          1 |
| 2850.00 |          1 |
| 2450.00 |          1 |
| 5000.00 |          1 |
| 1500.00 |          1 |
|  950.00 |          1 |
| 3000.00 |          1 |
| 1300.00 |          1 |
+---------+------------+
11 rows in set (0.00 sec)
方法二：
mysql> select sal,count(*) from emp group by sal having count(sal)>1;
+---------+----------+
| sal     | count(*) |
+---------+----------+
| 1250.00 |        2 |
+---------+----------+
1 row in set (0.00 sec)

#查询每个员工工资与emp表的平均工资之间的差距。
mysql> select ename,sal - (select avg(sal) from emp) from emp;
+--------+----------------------------------+
| ename  | sal - (select avg(sal) from emp) |
+--------+----------------------------------+
| SMITH  |                     -1277.083333 |
| ALLEN  |                      -477.083333 |
| WARD   |                      -827.083333 |
| JONES  |                       897.916667 |
| MARTIN |                      -827.083333 |
| BLAKE  |                       772.916667 |
| CLARK  |                       372.916667 |
| KING   |                      2922.916667 |
| TURNER |                      -577.083333 |
| JAMES  |                     -1127.083333 |
| FORD   |                       922.916667 |
| MILLER |                      -777.083333 |
+--------+----------------------------------+
12 rows in set (0.00 sec)

mysql> select sal,count(*) from emp group by sal having count(sal)>1;
+---------+----------+
| sal     | count(*) |
+---------+----------+
| 1250.00 |        2 |
+---------+----------+
1 row in set (0.00 sec)

#查询emp表最高工资与平均工资的差距。
mysql> select max(sal) - (select avg(sal) from emp) from emp;
+---------------------------------------+
| max(sal) - (select avg(sal) from emp) |
+---------------------------------------+
|                           2922.916667 |
+---------------------------------------+
1 row in set (0.00 sec)

#查询每个员工的名称及其工种的名称。
mysql> select ename,job from emp;
+--------+-----------+
| ename  | job       |
+--------+-----------+
| SMITH  | CLERK     |
| ALLEN  | SALESMAN  |
| WARD   | SALESMAN  |
| JONES  | MANAGER   |
| MARTIN | SALESMAN  |
| BLAKE  | MANAGER   |
| CLARK  | MANAGER   |
| KING   | PRESIDENT |
| TURNER | SALESMAN  |
| JAMES  | CLERK     |
| FORD   | ANALYST   |
| MILLER | CLERK     |
+--------+-----------+
12 rows in set (0.00 sec)

#查询哪个工种的人数最多，要求列出这种工种的完整名称及其人数。
方法一：
mysql> select job,count(1) from emp group by job;
+-----------+----------+
| job       | count(1) |
+-----------+----------+
| CLERK     |        3 |
| SALESMAN  |        4 |
| MANAGER   |        3 |
| PRESIDENT |        1 |
| ANALYST   |        1 |
+-----------+----------+
5 rows in set (0.00 sec)
方法二：
mysql> select job,count(*) from emp group by job order by count(*) desc limit 1;
+----------+----------+
| job      | count(*) |
+----------+----------+
| SALESMAN |        4 |
+----------+----------+
1 row in set (0.00 sec)

#查询哪个部门的员工个数最多，要求列出此部门编号及其员工个数。
mysql> select deptno,count(*) from emp group by deptno order by count(*) desc limit 1;
+--------+----------+
| deptno | count(*) |
+--------+----------+
|     30 |        6 |
+--------+----------+
1 row in set (0.01 sec)

#查询每年的入职人数，要求列出相应年份及入职人数，查询结果以年份排序。
mysql> select year(hiredate),count(*) from emp group by year(hiredate) order   
        by year(hiredate) asc;
+----------------+----------+
| year(hiredate) | count(*) |
+----------------+----------+
|           1980 |        1 |
|           1981 |       10 |
|           1982 |        1 |
+----------------+----------+
3 rows in set (0.00 sec)

#查询哪个部门的平均工资最高，要求列出部门名称及其平均工资额。
mysql> select deptno,avg(sal) from emp group by deptno;
+--------+-------------+
| deptno | avg(sal)    |
+--------+-------------+
|     10 | 2916.666667 |
|     20 | 2258.333333 |
|     30 | 1566.666667 |
+--------+-------------+
3 rows in set (0.00 sec

#查询哪些工种的平均工资高于2000，要求列出工种名称及其平均工资额。
mysql> select avg(sal),job from emp group by job having avg(sal)>2000;
+-------------+-----------+
| avg(sal)    | job       |
+-------------+-----------+
| 2758.333333 | MANAGER   |
| 5000.000000 | PRESIDENT |
| 3000.000000 | ANALYST   |
+-------------+-----------+
3 rows in set (0.00 sec)

#利用find命令(或其他命令)，查询mysql和mysqld在哪个目录下。
Mysql：
[root@law ~]# find / -iname mysql
/etc/logrotate.d/mysql
/etc/selinux/targeted/active/modules/100/mysql
/var/lib/mysql
/var/lib/mysql/mysql
/usr/bin/mysql
/usr/lib64/mysql
Mysqld：
[root@law ~]# find / -iname mysqld
/run/mysqld
/usr/sbin/mysqld

查询

# 查询每个部门分别是哪个员工获得了其所在部门的最高工资，要求列出其名称、部门名称及其工资额。
select e.ename,dept.dname,a.max_sal
from
emp e,
dept,
(select deptno,max(sal) as max_sal from emp group by deptno) a
where
e.deptno = dept.deptno
and
a.deptno = e.deptno
and
a.max_sal = e.sal
结果：
+-------+------------+---------+
| ename | dname | max_sal |
+-------+------------+---------+
| KING | ACCOUNTING | 5000.00 |
| FORD | RESEARCH | 3000.00 |
| BLAKE | SALES | 2850.00 |
+-------+------------+---------+
3 rows in set (0.00 sec)

#查询工资超过平均工资的员工个数
mysql> select count(sal) from emp where sal>(select avg(sal) from emp);         +------------+
| count(sal) |
+------------+
|          5 |
+------------+
1 row in set (0.00 sec)

#查询每个部门中，超过部门平均工资的员工姓名。
select deptno,ename from emp
where
sal>(select avg(sal) from emp where emp.deptno = deptno)
结果：
+--------+-------+
| deptno | ename |
+--------+-------+
|     20 | JONES |
|     30 | BLAKE |
|     10 | CLARK |
|     10 | KING  |
|     20 | FORD  |
+--------+-------+
5 rows in set (0.00 sec)

索引

#在emp表的ename列创建索引idx_ename，确认索引已创建。
mysql> create index idx_ename on emp(ename);
Query OK, 0 rows affected (0.03 sec)
Records: 0  Duplicates: 0  Warnings: 0
mysql> show index from emp\G;
*************************** 1. row ***************************
        Table: emp
   Non_unique: 1
     Key_name: idx_ename
 Seq_in_index: 1
  Column_name: ename
    Collation: A
  Cardinality: 12
     Sub_part: NULL
       Packed: NULL
         Null: YES
   Index_type: BTREE
      Comment:
Index_comment:
      Visible: YES
1 row in set (0.00 sec)

ERROR:
No query specified

#执行下面命令对emp表添加一行记录：
mysql> insert into emp(empno, ename, sal, deptno)
-> values(9999, 'MIKE', 3000.00, 10);
重新执行show index from emp，查看索引的Cardinality是否变化，说明了什么问题。执行下面命令对emp表重新计算统计信息，再次查询其Cardinality是否变化。
mysql> analyze table emp;
重新分析

#查看下面查询的执行计划，确认其是否使用了idx_ename索引。
#select * from emp where ename = 'SMITH'
mysql> explain select * from emp where ename = 'SMITH'\G;
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: emp
   partitions: NULL
         type: ref
possible_keys: idx_ename
          key: idx_ename
      key_len: 43
          ref: const
         rows: 1
     filtered: 100.00
        Extra: NULL
1 row in set, 1 warning (0.00 sec)
ERROR:
No query specified

#select * from emp where ename like 'S%'
mysql> explain select * from emp where ename like 'S%'\G;
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: emp
   partitions: NULL
         type: range
possible_keys: idx_ename
          key: idx_ename
      key_len: 43
          ref: NULL
         rows: 1
     filtered: 100.00
        Extra: Using index condition
1 row in set, 1 warning (0.04 sec)
ERROR:
No query specified

#select * from emp where ename like '%S'
mysql> explain select * from emp where ename like '%S'\G;
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: emp
   partitions: NULL
         type: ALL
possible_keys: NULL
          key: NULL
      key_len: NULL
          ref: NULL
         rows: 13
     filtered: 11.11
        Extra: Using where
1 row in set, 1 warning (0.00 sec)
ERROR:
No query specified

#删除idx_ename索引。
mysql> drop index idx_ename on emp;
Query OK, 0 rows affected (0.09 sec)
Records: 0  Duplicates: 0  Warnings: 0

#执行下面命令在ename和sal列上创建复合索引idx_ename_sal，确认索引已创建。
mysql> create index idx_ename_sal on emp(ename, sal);

#下面哪个查询会使用以上idx_ename_sal。
select * from emp where ename = 'SMITH'
select * from emp where sal = 1000
select * from emp where ename = 'SMITH' and sal = 1000
select * from emp where sal = 1000 and ename = 'SMITH'

#下面命令，查看表连接的执行计划。
mysql> explain
    -> select e.ename, d.dname
    -> from emp e, dept d
    -> where e.deptno = d.deptno
    -> \G

#创建big_table存储过程后，执行call big_table(100000)，创建big_table表，并对其添加10万行记录，在id列上创建索引idx_id，下面查询是否会用到此索引：
mysql>select big_table from t where id = 1000
#执行下面update命令：
mysql>update big_table set id = 1000 where id >= 1001;
#执行下面命令重新计算big_table的统计信息：
mysql> analyze table big_table;
#再次查看下面命令是否使用了idx_id索引：
mysql>select * from big_table where id = 1000
#执行下面命令统计id列的直方图后，以上查询是否会使用索引
mysql> analyze table big_table update histogram on length with 1000 buckets;

逻辑备份

#执行select into outfile导出dept表，清空dept表后由逻辑备份执行load data导入数据。
mysql> select * from dept into outfile '/var/lib/mysql-files/dept.ckp'
    -> ;
Query OK, 4 rows affected (0.00 sec)
mysql> truncate table dept;
Query OK, 0 rows affected (0.06 sec)
mysql> select * from dept;
Empty set (0.00 sec)
mysql> edit
    -> \p
--------------
load data infile '/var/lib/mysql-files/dept.ckp'
into table dept
--------------
    -> ;
Query OK, 4 rows affected (0.10 sec)
Records: 4  Deleted: 0  Skipped: 0  Warnings: 0
mysql> select * from dept;
+--------+------------+----------+
| deptno | dname      | loc      |
+--------+------------+----------+
|     10 | ACCOUNTING | NEW YORK |
|     20 | RESEARCH   | DALLAS   |
|     30 | SALES      | CHICAGO  |
|     40 | OPERATIONS | BOSTON   |
+--------+------------+----------+
4 rows in set (0.00 sec)
[root@law mysql-files]# ls
dept_bak.CSV  dept.bkp  dept.ckp  dept.sql  dept.txt
[root@law mysql-files]# cat dept.ckp
10      ACCOUNTING      NEW YORK
20      RESEARCH        DALLAS
30      SALES   CHICAGO
40      OPERATIONS      BOSTON

欢迎技术交流

WeChat......

最后编辑于：2019.02.12 22:18:33

人面猴
序言：七十年代末，一起剥皮案震惊了整个滨河市，随后出现的几起案子，更是在滨河造成了极大的恐慌，老刑警刘岩，带你破解...
沈念sama阅读 194,088评论 5赞 459
死咒
序言：滨河连续发生了三起死亡事件，死亡现场离奇诡异，居然都是意外死亡，警方通过查阅死者的电脑和手机，发现死者居然都...
沈念sama阅读 81,715评论 2赞 371
救了他两次的神仙让他今天三更去死
文/潘晓璐我一进店门，熙熙楼的掌柜王于贵愁眉苦脸地迎上来，“玉大人，你说我怎么就摊上这事。” “怎么了？”我有些...
开封第一讲书人阅读 141,361评论 0赞 319
道士缉凶录：失踪的卖姜人
文/不坏的土叔我叫张陵，是天一观的道长。经常有香客问我，道长，这世上最难降的妖魔是什么？我笑而不...
开封第一讲书人阅读 52,099评论 1赞 263
港岛之恋（遗憾婚礼）
正文为了忘掉前任，我火速办了婚礼，结果婚礼上，老公的妹妹穿的比我还像新娘。我一直安慰自己，他们只是感情好，可当我...
茶点故事阅读 60,987评论 4赞 355
恶毒庶女顶嫁案：这布局不是一般人想出来的
文/花漫我一把揭开白布。她就那样静静地躺着，像睡着了一般。火红的嫁衣衬着肌肤如雪。梳的纹丝不乱的头发上，一...
开封第一讲书人阅读 46,063评论 1赞 272
城市分裂传说
那天，我揣着相机与录音，去河边找鬼。笑死，一个胖子当着我的面吹牛，可吹牛的内容都是我干的。我是一名探鬼主播，决...
沈念sama阅读 36,486评论 3赞 381
双鸳鸯连环套：你想象不到人心有多黑
文/苍兰香墨我猛地睁开眼，长吁一口气：“原来是场噩梦啊……” “哼！你这毒妇竟也来了？” 一声冷哼从身侧响起，我...
开封第一讲书人阅读 35,175评论 0赞 253
万荣杀人案实录
序言：老挝万荣一对情侣失踪，失踪者是张志新（化名）和其女友刘颖，没想到半个月后，有当地人在树林里发现了一具尸体，经...
沈念sama阅读 39,440评论 1赞 290
护林员之死
正文独居荒郊野岭守林人离奇死亡，尸身上长有42处带血的脓包…… 初始之章·张勋以下内容为张勋视角年9月15日...
茶点故事阅读 34,518评论 2赞 309
白月光启示录
正文我和宋清朗相恋三年，在试婚纱的时候发现自己被绿了。大学时的朋友给我发了我未婚夫和他白月光在一起吃饭的照片。...
茶点故事阅读 36,305评论 1赞 326
活死人
序言：一个原本活蹦乱跳的男人离奇死亡，死状恐怖，灵堂内的尸体忽然破棺而出，到底是诈尸还是另有隐情，我是刑警宁泽，带...
沈念sama阅读 32,190评论 3赞 312
日本核电站爆炸内幕
正文年R本政府宣布，位于F岛的核电站，受9级特大地震影响，放射性物质发生泄漏。R本人自食恶果不足惜，却给世界环境...
茶点故事阅读 37,550评论 3赞 298
男人毒药：我在死后第九天来索命
文/蒙蒙一、第九天我趴在偏房一处隐蔽的房顶上张望。院中可真热闹，春花似锦、人声如沸。这庄子的主人今日做“春日...
开封第一讲书人阅读 28,880评论 0赞 17
一桩弑父案，背后竟有这般阴谋
文/苍兰香墨我抬头看了看天上的太阳。三九已至，却和暖如春，着一层夹袄步出监牢的瞬间，已是汗流浃背。一阵脚步声响...
开封第一讲书人阅读 30,152评论 1赞 250
情欲美人皮
我被黑心中介骗来泰国打工，没想到刚下飞机就差点儿被人妖公主榨干…… 1. 我叫王不留，地道东北人。一个月前我还...
沈念sama阅读 41,451评论 2赞 341
代替公主和亲
正文我出身青楼，却偏偏与公主长得像，于是被迫代替她去往敌国和亲。传闻我的和亲对象是个残疾皇子，可洞房花烛夜当晚...
茶点故事阅读 40,637评论 2赞 335

Msql学习-例子

表视图：

Mysql简单select句子

汇总函数

查询

索引

逻辑备份

推荐阅读更多精彩内容