在本篇文章中将给大家讲解下msyql中now()、sysdate()、curdate()区别:

SELECT date_sub(date_sub(date_format(now(),'%y-%m-%d '),interval extract( day from now())-1 day),interval 1 month);

select date_sub('2019-06-01',interval 1 month);

上个月第一天

select date_sub(date_sub(date_format(now(),'%y-%m-%d'),interval extract( day from now()) day),interval 0 month)

上个月最后一天

select date_sub(date_sub(date_format(now(),'%y-%m-%d'),interval extract( day from now())-1 day),interval 0 month)

select date_format(now(),'%Y-%m-01 ');

这个月第一天

Mysql日志管理

error log 错误日志 排错 /var/log/mysqld.log【默认开启】

bin log 二进制日志 备份 增量备份 DDL DML DCL

Relay log 中继日志 复制 接收 replication master

slow log 慢查询日志 调优 查询时间超过指定值

Error Log

log-error=/var/log/mysqld.log

Binary Log(用于备份恢复数据)

产生binlog日志:

log-bin=/var/log/mysql-bin/slave2

serve-id=2

mkdir /var/log/mysql-bin/slave2

#chmod mysql.mysql /var/log/mysql-bin/slave

#systemctl restart mysqld

  1. 重启mysqld 会截断旧日志产生新的日志

  2. 刷新日志会截断旧日志产生新的日志

mysql> flush logs

  1. 删除所有binlog(禁用)

mysql> reset master

  1. 删除部分日志

mysql> PURGE BINARY LOGS TO 'mysql-bin.010';

mysql> PURGE BINARY LOGS BEFORE '2016-04-02 22:46:26';

  1. 暂停binlog日志功能(仅对当前会话生效)

mysql> SET SQL_LOG_BIN=0;

mysql> SET SQL_LOG_BIN=1;

读取binlog日志:

mysqlbinlog mysql.000002

按datetime读取:

mysqlbinlog mysql.000002 --start-datetime="2018-12-05 10:02:56"

mysqlbinlog mysql.000002 --stop-datetime="2018-12-05 11:02:54"

mysqlbinlog mysql.000002 --start-datetime="2018-12-05 10:02:56" --stop-datetime="2018-12-05 11:02:54"

按position读取:

mysqlbinlog mysql.000002 --start-position=260

mysqlbinlog mysql.000002 --stop-position=260

mysqlbinlog mysql.000002 --start-position=260 --stop-position=930

查看带加密的binlong日志

mysqlbinlog ---output=decode-rows -v 日志文件

根据binlog恢复数据:

根据时间点恢复数据

mysqlbinlog --start-datetime='2014-11-25 11:56:54' --stop-datetime='2014-11-25 11:57:41' tiger-bin.000001 | mysql -u root -p1

根据位置点恢复数据

mysqlbinlog --start-position 106 --stop-position 527 tiger-bin.000001 | mysql -u root -p1

刷新bin-log日志:

#mysqladmin flush-logs

去除binlog加密:

transaction_isolation=repeatable-read

binlog_format=mixed

慢查询:

slow_query_log=1

slow_query_log_file=/var/log/mysql-slow/slow.log

long_query_time=3

mkdir /var/log/mysql-slow/

chown mysql.mysql /var/log/mysql-slow/

systemctl restart mysqld

查看慢查询日志

测试:BENCHMARK(count,expr)

SELECT BENCHMARK(50000000,2*3)