魅惑青花瓷

场景：每天只能存在一个时间段的公告，添加公告时，不能添加有交集的公告信息SET @a = '2020-06-17 20:00:00';SET @b = '2020-06-28 00:00:00';SELECT *FROM testWHERE ( begin_time >= @a AND begin_time <= @b )OR ( begin_time <= @a AND end_time >= @b)OR ( end_time >=.

1.下载压缩版2.cmd管理员运行，到mysql解压目录/bin目录，执行mysqld -install3.执行net start mysql启动4.启动成功后，修改密码5.执行mysqld --console --skip-grant-tables --shared-memory，跳过授权6.新的cmd，管理员运行use mysql;ALTER USER ‘root’@‘localhost’ IDENTIFIED WITH mysql_native_password BY ‘新密码’;FL

1.找到mysql安装目录，如果找不到，可以，计算机-管理-找到mysql2.切换到mysql安装目录的bin目录下，cmd2.1登录 mysql -u root -p2.2跳出输入密码2.3mysql>use dbtest;2.4mysql>set names utf8;2.5mysql>source D:/www/sql/back.sql;如果不确...

select time1, time2, time3 from tableName order by time1 is null, time1 and time2 is null , time2 and time3 is null , time3

使用source导入超大文件步骤1 打开mysql安装目录，cmd2登录mysql -h localhost -u root -p依次键入命令mysql&amp;gt;use dbtest;mysql&amp;gt;set names utf8;（这一步，可以防止导入的sql中的中文乱码）mysql&amp;gt;source D:/www/sql/back.sql;...

mysql函数使用集合整理（后续有用到的函数，会添加进来）FIND_IN_SETSELECT * FROM student WHERE FIND_IN_SET(值, 字段名);

将only_full_goup_by替换为空##当前session变量生效SET sql_mode=(SELECT REPLACE(@@sql_mode,‘ONLY_FULL_GROUP_BY’,’’));##全局变量生效SET global sql_mode=(SELECT REPLACE(@@sql_mode,‘ONLY_FULL_GROUP_BY’,’’));...

1.查看mysql最大连接数show variables like ‘%max_connections%’;2.修改mysql最大连接数set global max_connections=1000;