Category: SQL

SELECT * FROM db_storage limit 1085031,20
查询时间为0.486s

SELECT * FROM db_storage WHERE ID >= (select id from db_storage limit 1085031, 1) limit 20

SELECT a.* FROM db_storage a INNER JOIN (SELECT id FROM db_storage LIMIT 1085031,20) b ON a.id = b.id;

上面两个类似，为0.27s左右，此处需要优化pagehelper 逻辑

[mysqld]
character-set-server=utf8mb4

[mysql]
default-character-set=utf8mb4

只要修改my.ini(位置:C:ProgramDataMySQL)文件,然后重启mysql服务即可.

注意数据库的编码为utf8mb4

SHOW VARIABLES LIKE 'character_set%';

 

SELECT
	COLUMN_NAME AS 列名,
	cast(COLUMN_TYPE as CHAR) AS 数据类型,
	cast(DATA_TYPE as CHAR) AS 字段类型,
	CHARACTER_MAXIMUM_LENGTH AS 长度,
	IS_NULLABLE AS 是否为空,
	COLUMN_DEFAULT AS 默认值,
	COLUMN_COMMENT AS 备注
FROM
	INFORMATION_SCHEMA. COLUMNS
WHERE
	table_schema = 'tobacco_asset'
AND 
        table_name = 'asset_base'

这样可以查出对应的表格每个字段的信息

1.安装以后没有设置密码

sudo cat /etc/mysql/debian.cnf

通过这个查看mysql的默认用户名和密码

# Automatically generated for Debian scripts. DO NOT TOUCH!
[client]
host     = localhost
user     = debian-sys-maint
password = cOrWdhKDBv7LS86s
socket   = /var/run/mysqld/mysqld.sock
[mysql_upgrade]
host     = localhost
user     = debian-sys-maint
password = cOrWdhKDBv7LS86s
socket   = /var/run/mysqld/mysqld.sock

2.正常登录mysql，修改密码

 alter user'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'root';
 flush privileges;

3.重新登陆即可

引用 https://www.cnblogs.com/shuilangyizu/p/8805384.html

--今天

select * from 表名 where to_days(时间字段名) = to_days(now());

--昨天

SELECT * FROM 表名 WHERE TO_DAYS( NOW( ) ) - TO_DAYS( 时间字段名) <= 1

AND TO_DAYS(NOW()) - TO_DAYS(update_time)>0

--本周 SELECT * FROM 表名 WHERE YEARWEEK( date_format( 时间字段名,'%Y-%m-%d' ) ) = YEARWEEK( now() ) ; --本月 SELECT * FROM 表名 WHERE DATE_FORMAT( 时间字段名, '%Y%m' ) = DATE_FORMAT( CURDATE( ) ,'%Y%m' ) --上一个月 SELECT * FROM 表名 WHERE PERIOD_DIFF(date_format(now(),'%Y%m'),date_format(时间字段名,'%Y%m') =1 --本年 SELECT * FROM 表名 WHERE YEAR( 时间字段名 ) = YEAR( NOW( ) ) --上一月 SELECT * FROM 表名 WHERE PERIOD_DIFF( date_format( now( ) , '%Y%m' ) , date_format( 时间字段名, '%Y%m' ) ) =1 --查询本季度数据 select * from `ht_invoice_information` where QUARTER(create_date)=QUARTER(now()); --查询上季度数据 select * from `ht_invoice_information` where QUARTER(create_date)=QUARTER(DATE_SUB(now(),interval 1 QUARTER)); --查询本年数据 select * from `ht_invoice_information` where YEAR(create_date)=YEAR(NOW()); --查询上年数据 select * from `ht_invoice_information` where year(create_date)=year(date_sub(now(),interval 1 year)); --查询当前这周的数据 SELECT name,submittime FROM enterprise WHERE YEARWEEK(date_format(submittime,'%Y-%m-%d')) = YEARWEEK(now()); --查询上周的数据 SELECT name,submittime FROM enterprise WHERE YEARWEEK(date_format(submittime,'%Y-%m-%d')) = YEARWEEK(now())-1; --查询当前月份的数据 select name,submittime from enterprise where date_format(submittime,'%Y-%m')=date_format(now(),'%Y-%m') --查询距离当前现在6个月的数据 select name,submittime from enterprise where submittime between date_sub(now(),interval 6 month) and now(); --查询上个月的数据 select name,submittime from enterprise where date_format(submittime,'%Y-%m')=date_format(DATE_SUB(curdate(), INTERVAL 1 MONTH),'%Y-%m') select * from ` user ` where DATE_FORMAT(pudate, ' %Y%m ' ) = DATE_FORMAT(CURDATE(), ' %Y%m ' ) ; select * from user where WEEKOFYEAR(FROM_UNIXTIME(pudate,'%y-%m-%d')) = WEEKOFYEAR(now()) select * from user where MONTH (FROM_UNIXTIME(pudate, ' %y-%m-%d ' )) = MONTH (now()) select * from [ user ] where YEAR (FROM_UNIXTIME(pudate, ' %y-%m-%d ' )) = YEAR (now()) and MONTH (FROM_UNIXTIME(pudate, ' %y-%m-%d ' )) = MONTH (now()) select * from [ user ] where pudate between 上月最后一天 and 下月第一天 where date(regdate) = curdate(); select * from test where year(regdate)=year(now()) and month(regdate)=month(now()) and day(regdate)=day(now()) SELECT date( c_instime ) ,curdate( ) FROM `t_score` WHERE 1 LIMIT 0 , 30

mysql分析当前的查询线程

select * from information_schema.`PROCESSLIST` where info is not null;

或者

show processList

 

联表更新

UPDATE tobacco_product AS p, `temp_公司商品维护（通用）` AS t SET p.ONLINE_DATE_YEAR = CONVERT(STR_TO_DATE(t.`入网日期`, “%Y”),int) WHERE p.CIG_UPCS_CD = t.`条包装条形码`

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