MySQL常用命令及SQL

1.查询支持引擎

mysql> show engines;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine | Support | Comment | Transactions | XA | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |
| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |
| CSV | YES | CSV storage engine | NO | NO | NO |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |
| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
8 rows in set (0.00 sec)
2.修改表引擎

mysql>show create table xxx;

mysql>alter table xxx engine=innodb;

 

3.逻辑备份恢复数据库

mysqldump -uroot -p*** --default-character-set=utf8  [dbname] -R -F > dbname.sql

mysql -uroot -p*** --default-character-set=utf8 [dbname] < dbname.sql

 

4.SQL取整函数

mysql> select floor(1.1);
+------------+
| floor(1.1) |
+------------+
|          1 |
+------------+
1 row in set (0.00 sec)
mysql> select ceil(1.1);
+-----------+
| ceil(1.1) |
+-----------+
|         2 |
+-----------+
1 row in set (0.00 sec)
mysql> select round(1.4);
+------------+
| round(1.4) |
+------------+
|          1 |
+------------+
1 row in set (0.00 sec)
mysql> select round(1.5);
+------------+
| round(1.5) |
+------------+
|          2 |
+------------+
1 row in set (0.00 sec)
mysql>

 5.查看表、字段信息

mysql> use information_schema;

Database changed

mysql> desc tables;

mysql> desc columns;

 

6.按顺序更新栏位

select @t:=0

update jay set x=@t:=@t+1;

 

7.查询数据库支持的语言集及选用的语言集(charset)

show variables like '%char%';

show charset;

 

8.日期转换date_format()

mysql> select DATE_FORMAT(NOW(), '%Y%m%d%H%i%s' ) date;
+----------------+
| date           |
+----------------+
| 20120713092749 |
+----------------+
1 row in set (0.00 sec)

9.Oracle rownum替代方法

mysql> set @rownum := 0;
Query OK, 0 rows affected (0.00 sec)
mysql> select @rownum := ifnull(@rownum,0)+1 as level,x from rownum;
+-------+------+
| level | x    |
+-------+------+
|     1 |    1 |
|     2 |    2 |
|     3 |    3 |
+-------+------+
3 rows in set (0.00 sec)

10.Oracle替代row_number() over (partition by)方法

mysql> create table  test (id int ,dept int ,salary decimal(10,2));
Query OK, 0 rows affected (0.01 sec)
mysql> insert into test values
-> (1,10,5500.00),
-> (2,10,4500.00),
-> (3,20,1900.00),
-> (4,20,4800.00),
-> (5,40,6500.00),
-> (6,40,14500.00),
-> (7,40,44500.00),
-> (8,50,6500.00),
-> (9,50,7500.00);
Query OK, 9 rows affected (0.00 sec)
Records: 9  Duplicates: 0  Warnings: 0
mysql> select * from test;
+------+------+----------+
| id   | dept | salary   |
+------+------+----------+
|    1 |   10 |  5500.00 |
|    2 |   10 |  4500.00 |
|    3 |   20 |  1900.00 |
|    4 |   20 |  4800.00 |
|    5 |   40 |  6500.00 |
|    6 |   40 | 14500.00 |
|    7 |   40 | 44500.00 |
|    8 |   50 |  6500.00 |
|    9 |   50 |  7500.00 |
+------+------+----------+
9 rows in set (0.00 sec)

SELECT
id,
dept,
salary,
rank
FROM
(
SELECT
tmp.id,
tmp.dept,
tmp.salary ,@rownum :=@rownum + 1,
IF(
@dept = tmp.dept ,@rank :=@rank + 1 ,@rank := 1
)AS rank,
@dept := tmp.dept
FROM
(
SELECT
id,
dept,
salary
FROM
test
ORDER BY
dept ASC,
salary DESC
)tmp,
(
SELECT
@rownum := 0,
@dept := NULL ,@rank := 0
)a
)result;
+------+------+----------+------+
| id   | dept | salary   | rank |
+------+------+----------+------+
|    1 |   10 |  5500.00 |    1 |
|    2 |   10 |  4500.00 |    2 |
|    4 |   20 |  4800.00 |    1 |
|    3 |   20 |  1900.00 |    2 |
|    7 |   40 | 44500.00 |    1 |
|    6 |   40 | 14500.00 |    2 |
|    5 |   40 |  6500.00 |    3 |
|    9 |   50 |  7500.00 |    1 |
|    8 |   50 |  6500.00 |    2 |
+------+------+----------+------+
9 rows in set (0.00 sec)

11.查询更改字段comment

SELECT
concat(
'alter table ',
table_name,
' modify ',
COLUMN_NAME,
' ',
column_type,
IF(
IS_NULLABLE = 'NO',
' NOT NULL ',
' DEFAULT NULL '
),
IF(
ifnull(COLUMN_default, '')= '',
'',
CONCAT(
' default ',
'''',
COLUMN_default,
''''
)
),
extra,
IF(
ifnull(COLUMN_COMMENT, '')= '',
'',
CONCAT(
' comment ',
'''',
COLUMN_COMMENT,
''''
)
),
';'
)
FROM
COLUMNS

11.计算QPS、TPS

QPS= Query Per Second

TPS= Transaction Per Secnd

 

mysql> SHOW GLOBAL STATUS LIKE 'Questions';
+---------------+----------+
| Variable_name | Value    |
+---------------+----------+
| Questions     | 29340533 |
+---------------+----------+
1 row in set (0.00 sec)
mysql> SHOW GLOBAL STATUS LIKE 'Uptime';
+---------------+---------+
| Variable_name | Value   |
+---------------+---------+
| Uptime        | 1392479 |
+---------------+---------+
1 row in set (0.00 sec)
mysql> SHOW GLOBAL STATUS LIKE 'Com_commit';
+---------------+--------+
| Variable_name | Value  |
+---------------+--------+
| Com_commit    | 687702 |
+---------------+--------+
1 row in set (0.00 sec)
mysql> SHOW GLOBAL STATUS LIKE 'Com_rollback';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Com_rollback  | 694   |
+---------------+-------+
1 row in set (0.01 sec)

 

QPS=Questions/Uptime
TPS=(Com_commit + Com_rollback)/Uptime

12.Kill Process

mysqladmin processlist|grep -i Sleep|awk '{print $2}';

mysqladmin processlist|grep -i Sleep|awk '{print $2}'|xargs -n 1 mysqladmin -uroot -p kill

shell:
for id in `mysqladmin processlist|grep -i locked|awk '{print $2}'`

do

   mysqladmin kill ${id}

done

 

13.将字符串转换为Int order by排序

select varchar+0|varchar*1 as int;

14.Instance Summary

select table_schema,

sum(data_length+index_length)/1024/1024 as total_mb,

sum(data_length)/1024/1024 as data_mb,

sum(index_length)/1024/1024 as index_mb,

count(*) as tables

from information_schema.tables

group by table_schema

order by 2 desc; 

15.Schema Summary

select table_name,engine,row_format, table_rows, avg_row_length,

(data_length+index_length)/1024/1024 as total_mb,

(data_length)/1024/1024 as data_mb,

(index_length)/1024/1024 as index_mb

from information_schema.tables

where table_schema= DATABASE()

order by 6 desc;

16.设定表空间

mysql> show variables like '%innodb_data_file%';
+-----------------------+------------------------+
| Variable_name         | Value                  |
+-----------------------+------------------------+
| innodb_data_file_path | ibdata1:10M:autoextend |
+-----------------------+------------------------+
1 row in set (0.00 sec)

vi /etc/my.cnf

innodb_data_file_path = ibdata1:10G;ibdata2:10G;ibdata3:10G;ibdata4:10G;ibdata5:10G:autoextend

17.innodb表独立表空间

vi /etc/my.cnf

innodb_file_per_table

18.mysqldump相关命令

mysqldump -p -R > /tmp/kin.sql -- 导出包括存储过程

mysqldump -p -R -d kin > /tmp/kin.sql --导出结构不导数据

mysqldump -p -R -t kin > /tmp/kin.sql --导出数据不导结构

mysqldump -p -R kin > /tmp/kin.sql --导出数据及结构

19.开启general log查看执行语句

set global general_log=1; --开启

set global general_log=0; --关闭

或者

vi /etc/my.cnf

log=/tmp/general.log

show variables like '%general%';

20.mysql执行SQL语句脚本

mysql -h<ip> -uroot -p -e 'sql statement'

mysql>source xxx.sql

21.SQL分组取最大值

SELECT * FROM (SELECT * FROM t2 ORDER BY gid,col2 DESC) tGROUP BY gid; 

22.构造rownum

mysql> SELECT STATUS FROM ref_number;
+--------+
| STATUS |
+--------+
|      1 |
|      2 |
|      3 |
|      5 |
|      7 |
+--------+
5 rows in set (0.00 sec)

mysql> SELECT
-> @rownum1 := @rownum1 + 1 AS rn,
-> ref.*
-> FROM
-> (SELECT @rownum1 := 0)rown,
-> (SELECT STATUS FROM ref_number)ref;
+------+--------+
| rn   | STATUS |
+------+--------+
|    1 |      1 |
|    2 |      2 |
|    3 |      3 |
|    4 |      5 |
|    5 |      7 |
+------+--------+
5 rows in set (0.00 sec)

23. timestamp

mysql> SELECT  UNIX_TIMESTAMP(now());
+-----------------------+
| UNIX_TIMESTAMP(now()) |
+-----------------------+
|            1357521521 |
+-----------------------+
1 row in set (0.00 sec)

mysql> SELECT FROM_UNIXTIME(1357521521);
+---------------------------+
| FROM_UNIXTIME(1357521521) |
+---------------------------+
| 2013-01-07 09:18:41       |
+---------------------------+
1 row in set (0.00 sec)