mysql速查手册

Posted 2021-09-03 zhiqiang

数据类型

tinyint 1字节 (-128,127) (0,128) 小整数类型
smallint 2 字节 (-32 768，32 767) (0，65 535)
mediumint 3 字节 (-8 388 608，8 388 607) (0，16 777 215)
int/integer 4 字节
bigint 8字节 超大整数
float 4字节 单精度浮点数
double 8字节 双精度
decimal M+2 定点数
char 0-255字节 定长字符串
varchar 0-65535 字节 变长字符串
text 0-65 535字节 长文本数据
mediumtext 0-16 777 215字节 中等长度文本数据
longtext 0-4 294 967 295字节 极大文本数据
date 3字节 YYYY-MM-DD日期
time 3字节 HH:MM:SS
year 1字节 YYYY年
datetime 字节 YYYY-MM-DD HH:MM:SS
timestamp 4字节 YYYYMMDD HHMMSS
enum 65535个 枚举类型

运算符

+ - * / %取余
= != < <= > >=
between 1 and 10; 1到10包含两端
in (1,2,3,4,5) ;not in (1,2,3,4,5)
is null ; is not null
like "%" 匹配多个 ; like "_" 匹配一个
and or not

常见函数

随机数 rand()
连接字符串 concat(\'中国\',\'打日本\')
转换小写 lcase(\'ABC\') lower
转换大写 upper ucase
去除空格 trim(str)
curdate()+0  返回20160916
curdate()  2016-09-16
curtime() 21:53:23
now()  2019-07-10 21:52:23日期时间
unix_timestamp(now())  返回时间戳 1562767275
from_unixtime( 1539659520)   返回 2018-10-16 11:12:00 
 from_unixtime(1515980716, \'%Y-%m-%d %H:%i:%S\')  2018-01-15 09:45:16 格式化时间
date_format(now(), \'%Y-%m-%d\') 2018-01-15
date( now())  2019-07-10 提取日期
year(\'2019-7-10\')  返回2019
 month(\'2016-04-28\')  4
day(now()) 11 返回天
hour(\'2019-12-6 14:7:50\')  14
minute(\'2019-12-6 14:7:50\') 7
second(\'2019-12-6 14:7:50\')  50
last_day(\'2019-12-6 14:7:50\')  2019-12-31 给定日期最后一天
quarter(\'2016-04-28\')  2 季度,1,2,3,4
dayofweek(\'2019-7-10\')  返回4  星期三 -1
weekday(\'2019-7-10\')  返回2  星期三+1
dayofyear(\'2019-7-10\') 返回今天是191天
to_days(\'2019-12-6 14:7:50\')  737764计算日期 d 距离 0000 年 1 月 1 日的天数
from_days(733627) 2008-08-08 同上相反
day(last_day(now())) 返回本月天数
date_add(\'2019-12-6 14:7:50\',INTERVAL 1 day) +1天
date_sub(\'2019-12-6 14:7:50\',INTERVAL 1 day) -1天
timestamp(\'2008-08-08\') 2008-08-08 00:00:00
版本version
聚合函数
avg(col) 平均值
count(*) 记录数
min(col) max(col)最小 最大值
sum(col)求和

标准查询

set names utf8; 设置编码
select * from biao 基本查询
select distinct id from biao 结果字段不重复
select  * from biao order by id desc ,time asc; 升序降序
select  * from biao group by sex having;  分组筛选
select  * from biao limit 4 返回4条
select  * from biao 4,3   返回3条,从第5条记录开始
select a,b,c from A inner join B on A.id = B.id; 内连接
select a,b,c from A,B where A.id=B.id;内连接
select * from A left join B on   A.id=B.id; 左连接
select * from A right join B on   A.id=B.id;右连接
select id from Table where id2 in(select id3 from Table2) 子查询
select id from Table where  find_in_set(type,"ssq,sd,pls")  查询分类
select   id as ID from A as a  别名
select * from A union all select * from B 合并结果集
select * from A union select * from B 去重复
SELECT id,title FROM article WHERE id<$id ORDER BY id desc LIMIT 1 上一篇
SELECT id,title FROM article WHERE id>$id ORDER BY id ASC LIMIT 1 下一篇
select count(distinct openid) as total from TB 统计记录去重复

高级查询

select * from list where to_days(FROM_UNIXTIME(createtime))=to_days(now()) 今天
where to_days(now())-to_days(FROM_UNIXTIME(createtime))<1 今天
where to_days(now())-to_days(FROM_UNIXTIME(createtime))=1 昨天
where  DATE_SUB(CURDATE(), INTERVAL 7 DAY) < date(FROM_UNIXTIME(createtime))近七天含今天
where  YEARWEEK(date_format(FROM_UNIXTIME(createtime),\'%Y-%m-%d\')) = YEARWEEK(now()) 本周
where  YEARWEEK(date_format(FROM_UNIXTIME(createtime),\'%Y-%m-%d\')) = YEARWEEK(now())-1 上周
where  DATE_SUB(CURDATE(), INTERVAL 30 DAY) < date(FROM_UNIXTIME(createtime))近30天含今天
where DATE_FORMAT(FROM_UNIXTIME(createtime), \'%Y%m\') = DATE_FORMAT(CURDATE(), \'%Y%m\') 查询本月
where PERIOD_DIFF(DATE_FORMAT(NOW(),\'%Y%m\'), DATE_FORMAT(FROM_UNIXTIME(createtime),\'%Y%m\')) =1 上月
where QUARTER(FROM_UNIXTIME(createtime))=QUARTER(NOW()) 本季度
where QUARTER(FROM_UNIXTIME(createtime))=QUARTER(DATE_SUB(NOW(),INTERVAL 1 QUARTER)) 上季度
where  YEAR(FROM_UNIXTIME(createtime))=YEAR(NOW()) 今年
where  YEAR(FROM_UNIXTIME(createtime))=YEAR(DATE_SUB(NOW(),INTERVAL 1 YEAR)) 去年

SELECT @rank := @rank + 1 AS rank,t.* FROM (SELECT @rank := 0) r, user AS t ORDER BY t.score DESC; 相同分数按照id小的在前,排名不重复

SELECT rank,score,id FROM ( SELECT USER .*, @c := IF ( @p = score, @c, @r ) AS rank, @p := score, @r := @r + 1 FROM USER, ( SELECT @p := NULL, @r := 1, @c := 0 ) r ORDER BY score DESC ) c; 相同排名重复后去掉后面

UPDATE user INNER JOIN (SELECT @rank := @rank + 1 AS rank,t.id FROM (SELECT @rank := 0) r, user AS t ORDER BY t.score DESC) t2 ON t2.id=user.id SET user.rank=t2.rank  更新表自身排名,更新前rank都是0,没有重复

UPDATE user INNER JOIN (SELECT rank,id FROM ( SELECT user.*, @c := IF ( @p = score, @c, @r ) AS rank, @p := score, @r := @r + 1 FROM user, ( SELECT @p := NULL, @r := 1, @c := 0 ) r ORDER BY score DESC ) c) t2 ON t2.id=user.id SET user.ranking=t2.rank  有重复同上

UPDATE userSET rank= rank+1 WHERE id=5 自动加一

SELECT * FROM user ORDER BY RAND() LIMIT 5; 随机数据性能低下1000以内

SELECT * FROM user  AS t1 JOIN (SELECT ROUND(RAND() * (SELECT MAX(id) FROM user)) AS id) AS t2 WHERE t1.id >= t2.id ORDER BY t1.id ASC LIMIT 2;连续的id高效率

SELECT * FROM user WHERE id >= ((SELECT MAX(id) FROM user)-(SELECT MIN(id) FROM user)) * RAND() + (SELECT MIN(id) FROM user) limit 2; 随机id不连续

select * from user where id<7 order by id desc limit 1; 上一条6
select * from user where id>7 limit 1;  下一条