1.统计列分类数目
mysql> select count(1) from test;
+----------+
| count(1) |
+----------+
| 9 |
+----------+
1 row in set (0.02 sec)
2.分组统计
mysql> select ename,count(1) from test group by ename;
+----------+----------+
| ename | count(1) |
+----------+----------+
| aaaaa | 3 |
| ccccc | 1 |
| def | 1 |
| newName2 | 1 |
| newName3 | 1 |
| newNane1 | 1 |
| ttttt | 1 |
+----------+----------+
7 rows in set (0.00 sec)
3.在分组的统计数据的基础上再进行相同的统计
mysql> select ename,count(1) from test group by ename with rollup;
+----------+----------+
| ename | count(1) |
+----------+----------+
| aaaaa | 3 |
| ccccc | 1 |
| def | 1 |
| newName2 | 1 |
| newName3 | 1 |
| newNane1 | 1 |
| ttttt | 1 |
| NULL | 9 |
+----------+----------+
8 rows in set (0.00 sec)
4.按分组统计的结果计数
mysql> select ename,count(1) from test group by ename having count(1) > 1;
+-------+----------+
| ename | count(1) |
+-------+----------+
| aaaaa | 3 |
+-------+----------+
1 row in set (0.00 sec)
5.统计总数量、最大值、最小值
mysql> select sum(age),max(age),min(age) from test;
+----------+----------+----------+
| sum(age) | max(age) | min(age) |
+----------+----------+----------+
| 112 | 81 | 1 |
+----------+----------+----------+
1 row in set (0.00 sec)
6.左右连接
mysql> create table emp( ename varchar(20), hiredate date, sal int(11), deptno int(11) );
Query OK, 0 rows affected (0.04 sec)
mysql> insert into emp(ename,hiredate,sal,deptno) values ('zzx','2000-01-01',2000,1), ('lisa','2003-02-01',4000,2), ('bjguan','
2004-04-02',5000,1), ('bzshen','2005-04-01',4000,3);
Query OK, 4 rows affected (0.00 sec)
Records: 4 Duplicates: 0 Warnings: 0
mysql> select * from emp;
+--------+------------+------+--------+
| ename | hiredate | sal | deptno |
+--------+------------+------+--------+
| zzx | 2000-01-01 | 2000 | 1 |
| lisa | 2003-02-01 | 4000 | 2 |
| bjguan | 2004-04-02 | 5000 | 1 |
| bzshen | 2005-04-01 | 4000 | 3 |
+--------+------------+------+--------+
4 rows in set (0.00 sec)
mysql> create table dept ( deptno int(11), deptname varchar(20) );
Query OK, 0 rows affected (0.05 sec)
mysql> insert into dept(deptno,deptname) values (1,'tech'), (2,'sale'), (3,'hr');
Query OK, 3 rows affected (0.01 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> select * from dept;
+--------+----------+
| deptno | deptname |
+--------+----------+
| 1 | tech |
| 2 | sale |
| 3 | hr |
+--------+----------+
3 rows in set (0.00 sec)
mysql> select ename,deptname from emp,dept where emp.deptno = dept.deptno;
+--------+----------+
| ename | deptname |
+--------+----------+
| zzx | tech |
| lisa | sale |
| bjguan | tech |
| bzshen | hr |
+--------+----------+
4 rows in set (0.00 sec)
mysql> select ename,deptname from emp
-> left join dept on emp.deptno = dept.deptno;
+--------+----------+
| ename | deptname |
+--------+----------+
| zzx | tech |
| lisa | sale |
| bjguan | tech |
| bzshen | hr |
+--------+----------+
4 rows in set (0.00 sec)
mysql> select * from emp;
+--------+------------+------+--------+
| ename | hiredate | sal | deptno |
+--------+------------+------+--------+
| zzx | 2000-01-01 | 2000 | 1 |
| lisa | 2003-02-01 | 4000 | 2 |
| bjguan | 2004-04-02 | 5000 | 1 |
| bzshen | 2005-04-01 | 4000 | 3 |
+--------+------------+------+--------+
4 rows in set (0.00 sec)
mysql> insert into emp (ename) values ('dony');
Query OK, 1 row affected (0.00 sec)
mysql> select ename,deptname from emp left join dept on emp.deptno = dept.deptno;
+--------+----------+
| ename | deptname |
+--------+----------+
| zzx | tech |
| lisa | sale |
| bjguan | tech |
| bzshen | hr |
| dony | NULL |
+--------+----------+
5 rows in set (0.00 sec)
mysql> select * from emp;
+--------+------------+------+--------+
| ename | hiredate | sal | deptno |
+--------+------------+------+--------+
| zzx | 2000-01-01 | 2000 | 1 |
| lisa | 2003-02-01 | 4000 | 2 |
| bjguan | 2004-04-02 | 5000 | 1 |
| bzshen | 2005-04-01 | 4000 | 3 |
| dony | NULL | NULL | NULL |
+--------+------------+------+--------+
5 rows in set (0.00 sec)
mysql> select ename,deptname from emp right join dept on emp.deptno = dept.deptno;
+--------+----------+
| ename | deptname |
+--------+----------+
| zzx | tech |
| bjguan | tech |
| lisa | sale |
| bzshen | hr |
+--------+----------+
4 rows in set (0.00 sec)
mysql> select ename,deptname from emp right join dept on dept.deptno=emp.deptno;
+--------+----------+
| ename | deptname |
+--------+----------+
| zzx | tech |
| bjguan | tech |
| lisa | sale |
| bzshen | hr |
+--------+----------+
4 rows in set (0.00 sec)
mysql> select * from emp where deptno in ( select deptno from dept);
+--------+------------+------+--------+
| ename | hiredate | sal | deptno |
+--------+------------+------+--------+
| zzx | 2000-01-01 | 2000 | 1 |
| lisa | 2003-02-01 | 4000 | 2 |
| bjguan | 2004-04-02 | 5000 | 1 |
| bzshen | 2005-04-01 | 4000 | 3 |
+--------+------------+------+--------+
4 rows in set (0.00 sec)
7.几种嵌套查询
mysql> select * from emp where deptno = ( select deptno from dept limit 1);
+--------+------------+------+--------+
| ename | hiredate | sal | deptno |
+--------+------------+------+--------+
| zzx | 2000-01-01 | 2000 | 1 |
| bjguan | 2004-04-02 | 5000 | 1 |
+--------+------------+------+--------+
2 rows in set (0.00 sec)
mysql> select * from emp where deptno in ( select deptno from dept );
+--------+------------+------+--------+
| ename | hiredate | sal | deptno |
+--------+------------+------+--------+
| zzx | 2000-01-01 | 2000 | 1 |
| lisa | 2003-02-01 | 4000 | 2 |
| bjguan | 2004-04-02 | 5000 | 1 |
| bzshen | 2005-04-01 | 4000 | 3 |
+--------+------------+------+--------+
4 rows in set (0.00 sec)
mysql> select emp.* from emp ,dept where emp.deptno = dept.deptno;
+--------+------------+------+--------+
| ename | hiredate | sal | deptno |
+--------+------------+------+--------+
| zzx | 2000-01-01 | 2000 | 1 |
| lisa | 2003-02-01 | 4000 | 2 |
| bjguan | 2004-04-02 | 5000 | 1 |
| bzshen | 2005-04-01 | 4000 | 3 |
+--------+------------+------+--------+
4 rows in set (0.00 sec)
8.组合查询
mysql> select deptno from emp union select deptno from dept;
+--------+
| deptno |
+--------+
| 1 |
| 2 |
| 3 |
| NULL |
+--------+
4 rows in set (0.00 sec)
mysql> select deptno from emp union all select deptno from dept;
+--------+
| deptno |
+--------+
| 1 |
| 2 |
| 1 |
| 3 |
| NULL |
| 1 |
| 2 |
| 3 |
+--------+
8 rows in set (0.00 sec)
mysql> select deptno from emp union select deptno from dept;
+--------+
| deptno |
+--------+
| 1 |
| 2 |
| 3 |
| NULL |
+--------+
4 rows in set (0.00 sec)
9.权限设置举例
mysql> grant select,update on test1.* to z1@localhost identified by 'test';
Query OK, 0 rows affected (0.00 sec)
[root@ ~]# mysql -uz1 -ptest
mysql> use test1;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
mysql> insert into emp(sal,deptno) values('2000',3);
ERROR 1142 (42000): INSERT command denied to user 'z1'@'localhost' for table 'emp'.
10.内置帮助的使用
mysql> ? contents
You asked for help about help category: "Contents"
For more information, type 'help <item>', where <item> is one of the following
categories:
Account Management
Administration
Compound Statements
Data Definition
Data Manipulation
Data Types
Functions
Functions and Modifiers for Use with GROUP BY
Geographic Features
Help Metadata
Language Structure
Plugins
Procedures
Storage Engines
Table Maintenance
Transactions
User-Defined Functions
Utility
mysql> ? data types
You asked for help about help category: "Data Types"
For more information, type 'help <item>', where <item> is one of the following
topics:
AUTO_INCREMENT
BIGINT
BINARY
BIT
BLOB
BLOB DATA TYPE
BOOLEAN
CHAR
CHAR BYTE
DATE
DATETIME
DEC
DECIMAL
DOUBLE
DOUBLE PRECISION
ENUM
FLOAT
INT
INTEGER
LONGBLOB
LONGTEXT
MEDIUMBLOB
MEDIUMINT
MEDIUMTEXT
SET DATA TYPE
SMALLINT
TEXT
TIME
TIMESTAMP
TINYBLOB
TINYINT
TINYTEXT
VARBINARY
VARCHAR
YEAR DATA TYPE
11.通过操作此表可以实现迅速修改表名等操作。
mysql> select * from information_schema.tables;
12.字段的长度测试
mysql> create table t1(id1 int,id2 int(5));
Query OK, 0 rows affected (0.06 sec)
mysql> desc t1;
+-------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| id1 | int(11) | YES | | NULL | |
| id2 | int(5) | YES | | NULL | |
+-------+---------+------+-----+---------+-------+
mysql> insert into t1 values(1,1);
Query OK, 1 row affected (0.01 sec)
mysql> select * from t1;
+------+------+
| id1 | id2 |
+------+------+
| 1 | 1 |
+------+------+
1 row in set (0.00 sec)
mysql> alter table t1 modify id1 int zerofill;
Query OK, 1 row affected (0.05 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> alter table t1 modify id2 int(5) zerofill;
Query OK, 1 row affected (0.05 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> insert into t1 values(1,1111111);
Query OK, 1 row affected (0.01 sec)
mysql> select * from t1;
+------------+---------+
| id1 | id2 |
+------------+---------+
| 0000000001 | 00001 |
| 0000000001 | 1111111 |
+------------+---------+
2 rows in set (0.00 sec)
