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---
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title: "Mysql 笔记"
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date: 2019-10-30T11:51:23+08:00
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lastmod: 2019-10-30T11:51:23+08:00
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tags: ["mysql"]
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categories: ["database"]
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---
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# MySQL 5.7 配置文件 my.cnf
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```
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[mysqld]
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datadir = /db/mysql
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socket = /var/lib/mysql/mysql.sock
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symbolic-links = 0
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log-timestamps = SYSTEM
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slow-query-log = 1
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slow-query-log-file = /var/log/mysqld/slow.log
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long-query-time = 8
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#log-queries-not-using-indexes = 1
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log-error = /var/log/mysqld/error.log
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pid-file = /var/run/mysqld/mysqld.pid
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max-connections = 1000
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max-connect-errors = 1000
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max-user-connections = 600
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interactive-timeout = 3600
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wait-timeout = 3600
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skip-name-resolve = 1
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lower-case-table-names = 1
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default-time-zone = '+08:00'
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character-set-server = utf8mb4
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sql-mode = NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES
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bind-address = 0.0.0.0
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table-open-cache = 2048
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default-storage-engine = innodb
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innodb-autoinc-lock-mode = 2
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innodb-flush-log-at-trx-commit = 0
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# 建议物理内存一半
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innodb-buffer-pool-size = 8G
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innodb-buffer-pool-instances = 8
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max-allowed-packet = 512M
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query-cache-size = 0
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query-cache-type = 0
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# 建议点分 ip 的最后一个数字
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server-id = 123
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# bin log
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#binlog-format = ROW
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#log-bin = /var/lib/mysql/mysql-bin
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#expire-logs-days = 3
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# relay log
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#read-only = 1
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#replicate-wild-do-table = db1.%
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#relay-log = /var/lib/mysql/mysql-relay-bin
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#slave-parallel-type = logical-clock
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```
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# 复制表结构
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```sql
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create table db1.t1 like db2.t2;
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create table db1.t1 select db2.t2 where 1=2;
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```
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# 复制表结构及其数据
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```sql
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create table db1.t1 select db2.t2 [where ...]
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```
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# 复制表数据
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```
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insert into db2.t2(column1, column2 ...)
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select column1, column2 ... from db1.t1 [where ...]
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```
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# 通过复制表文件来复制表数据
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- 在db2中创建同结构表
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```sql
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create table db2.t1 like db1.t1;
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```
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- 丢弃表空间
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```sql
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alter table db2.t1 discard tablespace;
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```
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- 复制 t1 的表数据文件
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```bash
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#关闭数据库
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systemctl stop mysqld
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cd /var/lib/mysql
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scp db1/t1.idb db2/t1.idb
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chown mysql.mysql db2/t1.idb
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#启动数据库
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systemctl start mysqld
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```
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- 导入表空间
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```sql
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alter table db2.t1 import tablespace;
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```
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# 设置一个表的空列自增
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```sql
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-- 删除可能存在的主键
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alter table 表名 drop primary key;
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alter table 表名 modify 列名 auto_increment primary key;
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```
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# 查看数据库中每个表的全部列名
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```sql
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select table_name, column_name from
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information_schema.columns
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where table_schema = '数据库名';
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```
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# 查看数据库中每个表的行数
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```sql
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select table_name, table_rows
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from information_schema.tables
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where table_schema = '数据库名';
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```
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# 查看数据库中每个表的索引
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```sql
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select table_name, column_name, index_name
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from INFORMATION_SCHEMA.STATISTICS
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where table_schema = '数据库名';
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```
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# 表的部分列数据到另一个表
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```sql
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update db2.t2(column1, column2 ...) = (
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select column1, column2 from db1.t1
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where db1.t1.id = db2.t2.id);
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```
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# 把语句执行结果写到文件
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```bash
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mysql -uroot -p -hsever_ip -Ddb_name
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-Ne "select ... from table_name;" > file_name
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```
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# 表分区
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- 查看表的分区情况
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```sql
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select table_schema, table_name, partition_name, table_rows
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from information_schema.partitions
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where table_name = 'table_name';
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```
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- 建表时指定
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```sql
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create table table_name(...)
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partition by range columns(column_name)
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(partition part_name values less than(some_value));
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```
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- 修改成分区表
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```sql
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alter table table_name
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partition by range(column_name)
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(partition part_name values less than(som_value));
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```
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- 增加分区
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```sql
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alter table table_name add partition
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(partition part_name values less than(som_value));
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```
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- 删除分区
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```sql
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alter table table_name drop partition part_name;
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```
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- 合并/拆分分区
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```sql
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alter table table_name
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reorganize part_old_1, part_old_2, part_old_3 into
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(partition part_new_1 values less than(value_1),
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partition part_new_2 values less than(value_2));
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```
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- 重建分区，整理分区碎片
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```sql
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alter table table_name
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rebuild partition part_name_1, part_name_2;
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```
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- 优化分区，回收空间，整理碎片
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```sql
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alter table table_name
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optimize partition part_name_1, part_name_2;
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```
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- 分析分区，读取并保存分区的健分布
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```sql
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alter table table_name
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analyze partition part_name_1, part_name_2;
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```
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- 修复分区
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```sql
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alter table table_name
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repair partition part_name_1, part_name_2;
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```
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- 检查分区
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```sql
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alter table table_name
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check partition part_name_1, part_name_2;
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```
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# MySQL 5.7 从库多线程同步
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```sql
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stop slave;
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set global slave_parallel_type='logical_clock';
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set global slave_parallel_workers=4;
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start slave;
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show processlist;
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```
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# MySQL 5.7 提示密码复杂度不够
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```sql
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set global validate_password_policy=0;
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```
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# MySQL 5.7 从库复制失败跳过指定数量的事务
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```sql
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stop slave;
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-- 跳过一个事务
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SET GLOBAL SQL_SLAVE_SKIP_COUNTER = 1;
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start slave;
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-- 修改 my.cnf
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slave-skip-errors=1062,1053,1146,1032 #跳过指定error no类型的错误
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slave-skip-errors=all #跳过所有错误
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```
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# MySQL 5.7 查看全部任务
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```sql
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-- 分号换成 \G 显示完整 sql
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show processlist;
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show full processlist;
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SELECT command FROM information_schema.processlist;
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```
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# MySQL 5.7 ssl 连接
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```
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--ssl-mode=REQUIRED
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```
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# MariaDB 10.1 修改密码
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```sql
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UPDATE user SET password=password('newpassword') WHERE user='root';
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```
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# MySQL 5.7 编码
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- 查看
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```sql
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SHOW VARIABLES LIKE 'character_set%';
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```
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- 数据库连接参数中，characterEncoding=utf8 会被自动识别为 utf8mb4，但是 autoReconnect=true 必须指定
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- 更改数据库编码
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```sql
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ALTER DATABASE db_name
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CHARSET UTF8MB4 COLLATE UTF8MB4_GENERAL_CI;
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```
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- 更改表编码
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```sql
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ALTER TABLE table_name
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CONVERT TO CHARSET UTF8MB4 COLLATE UTF8MB4_GENERAL_CI;
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```
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# MySQL 5.7 升级数据库管理表结构
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```bash
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mysql_upgrade -u root -p
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```
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# MySQL 5.7 误删 root 后恢复 root 账户
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- 停止 mysql 服务
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```bash
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systemctl stop mysqld
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```
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- 修改 my.cnf
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```
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# 添加如下一行
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skip-grant-tables
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```
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- 启动 mysql 服务
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```bash
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systemctl start mysqld
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```
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- 重建 root 账户，并授权
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```sql
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insert into user
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set user='root',
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ssl_cipher='',
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x509_issuer='',
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x509_subject='';
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update user
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set Host='localhost',
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select_priv='y',
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insert_priv='y',
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update_priv='y',
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Alter_priv='y',
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delete_priv='y',
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create_priv='y',
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drop_priv='y',
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reload_priv='y',
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shutdown_priv='y',
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Process_priv='y',
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file_priv='y',
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grant_priv='y',
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References_priv='y',
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index_priv='y',
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create_user_priv='y',
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show_db_priv='y',
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super_priv='y',
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create_tmp_table_priv='y',
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Lock_tables_priv='y',
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execute_priv='y',
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repl_slave_priv='y',
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repl_client_priv='y',
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create_view_priv='y',
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show_view_priv='y',
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create_routine_priv='y',
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alter_routine_priv='y',
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create_user_priv='y',
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event_priv='y',
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trigger_priv='y',
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create_tablespace_priv='y'
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where user='root';
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flush privileges;
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```
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- 停止 mysql 服务
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```bash
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systemctl stop mysqld
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```
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- 修改 my.cnf
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```
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# 删除刚添加的如下一行
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#skip-grant-tables
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```
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- 启动 mysql 服务，root 账户正常可用
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```bash
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systemctl start mysqld
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```
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# 通过EXPLAIN分析SQL的执行计划
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- 使用
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```sql
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explain sql
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```
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- select_type 查询类型
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- SIMPLE 简单表，没有表连接或子查询
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- PRIMARY 最外层的查询
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- UNION union语句的后置查询
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- SUBQUERY 第一个子查询
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- table 表/别名
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- type 访问类型
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- ALL 全表扫描
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- index 全索引扫描
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- range 索引范围扫描
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- ref 非唯一索引扫描
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- eq_ref 唯一索引扫描
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- const,system 单表最多一个匹配行
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- NULL 不需要扫描表或索引
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- possible_keys 查询可能使用的索引
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- key 实际使用的索引
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- key_len 使用的索引字段的长度
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- ref 其他匹配字段
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- rows 扫描行的数量
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- filtered 满足查询条件的记录占存储引擎返回记录的比例
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- Extra 执行情况说明
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- Using Index 全部使用索引，没有回表查询
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- Using Where 有回表查询
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- Using Index Condition ICP优化，直接在存储引擎完成条件过滤
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- Using Flesort 依靠索引顺序达不到排序效果，需额外排序
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# 统计 insert、delete、update 和 select 次数
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```sql
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show global status where Variable_name in
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('com_insert', 'com_delete', 'com_update', 'com_select');
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```
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# csv 文件
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- 导出
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```
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# Shell 终端
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# mysql -e "select * from t1
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into outfile '/var/lib/mysql-files/t1.csv'
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fields terminated by ','
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enclosed by '\"'
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escaped by '\\\'
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lines terminated by '\n'"
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# MySQL 终端
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# MySQL> select * from t1
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into outfile '/var/lib/mysql-files/t1.csv'
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fields terminated by ','
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enclosed by '\"'
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escaped by '\\'
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lines terminated by '\n';
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```
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- 导入
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```
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# Shell 终端
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# mysql -e "load data infile '/var/lib/mysql-files/t1.csv'
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into table t1
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fields terminated by ','
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enclosed by '\"'
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escaped by '\\\'
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lines terminated by '\n'"
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# MySQL 终端
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# MySQL> load data infile '/var/lib/mysql-files/t1.csv'
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into table t1
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fields terminated by ','
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enclosed by '\"'
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escaped by '\\'
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lines terminated by '\n';
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```
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