mysql开发之---每日一得01

2015年7月7日-------------------------

1、truncate表会清空建表语句auto_increment的值；某个表的id即是主键也是自增，你可以选择插入任意id值，如果不从1开始插入，从3开始insert，再插入没有id的值时，自增值是4

2、查看每种引擎的索引大小，来优化数据库参数
SELECT  ENGINE,  
ROUND(SUM(data_length) /1024/1024, 1) AS "Data MB",  
ROUND(SUM(index_length)/1024/1024, 1) AS "Index MB",  
ROUND(SUM(data_length + index_length)/1024/1024, 1) AS "Total MB",  
COUNT(*) "Num Tables"  
FROM  INFORMATION_SCHEMA.TABLES  
WHERE  table_schema not in ("information_schema", "performance_schema")  
GROUP BY  ENGINE; 

3、使用prepare stmt from准备一个动态sql语句时，主要
（1）被准备的语句定义时必须是会话级的变量不能是local变量，需要加@进行定义，准备后的语句直到会话结束才会丢失，可以使用deallocate prepare stmt消除分配的语句
表名不确定，检查这个表最大id，从id+1开始插入10行数据
BEGIN
-- 在存储过程中，一般的sql中values可以是变量，但是表名、字段名不能是变量
declare v_xname varchar(20) default 'testincre1';
delete from test.testincre1 where id=1;
select ifnull(max(id),0)+1 into @incre from test.testincre1;
set @end=@incre+10;
repeat
 set @sql=concat('insert into test.',v_xname,' values(@incre,''yangsq'',now());');
 select @sql;
 prepare stmt from @sql;
 execute stmt;
 deallocate prepare stmt;
set @incre=@incre+1;
until @incre=@end end repeat;
END
4、sql_slave_skip_counter
Last_SQL_Error: Error 'Unknown table 'sakila.testrepldb'' on query. Default database: 'sakila'. Query: 'DROP TABLE `testrepldb` /* generated by server */'
mysql> start slave sql_thread; 报错：会反复执行引起错误的sql，但是io_thread仍然正常会接受
2015-07-08 10:42:25 12378 [Warning] Slave SQL: If a crash happens this configuration does not guarantee that the relay log info will be consistent, Error_code: 0
2015-07-08 10:42:25 12378 [Note] Slave SQL thread initialized, starting replication in log 'mysql-bin.000012' at position 4449, relay log './yaolansvr_slave01-relay-bin.000014' position: 283
2015-07-08 10:42:25 12378 [ERROR] Slave SQL: Error 'Unknown table 'sakila.testrepldb'' on query. Default database: 'sakila'. Query: 'DROP TABLE `testrepldb` /* generated by server */', Error_code: 1051
2015-07-08 10:42:25 12378 [Warning] Slave: Unknown table 'sakila.testrepldb' Error_code: 1051
2015-07-08 10:42:25 12378 [ERROR] Error running query, slave SQL thread aborted. Fix the problem, and restart the slave SQL thread with "SLAVE START". We stopped at log 'mysql-bin.000012' position 4449

select @@sql_slave_skip_counter;
stop slave;--或者stop slave sql_thread
set global sql_slave_skip_counter=1;
start slave;

--log-error:
2015-07-08 10:53:30 12378 [Warning] Slave SQL: If a crash happens this configuration does not guarantee that the relay log info will be consistent, Error_code: 0
2015-07-08 10:53:30 12378 [Note] Slave SQL thread initialized, starting replication in log 'mysql-bin.000012' at position 4449, relay log './yaolansvr_slave01-relay-bin.000014' position: 283
2015-07-08 10:53:30 12378 [Note] 'SQL_SLAVE_SKIP_COUNTER=1' executed at relay_log_file='./yaolansvr_slave01-relay-bin.000014', relay_log_pos='283', master_log_name='mysql-bin.000012', master_log_pos='4449' and new position at relay_log_file='./yaolansvr_slave01-relay-bin.000014', relay_log_pos='410', master_log_name='mysql-bin.000012', master_log_pos='4576' 

5、从 sqlserver 查询mysql 报错 从数据类型 dbtype_dbtimestamp 转化为 datetime 时出错
mysql某表datetime类型数据是0028-01-01 00:00:00，插入sqlserver datetime报错，sqlserver datime支持的日期类型范围是1753 年 1 月 1 日到 9999 年 12 月 31 日

6、replicate的相关参数比较
--replicate-do-table：没有like pattern的功能，多个表需要指定多次
--replicate-wild-do-table：用like pattern的功能Example: --replicate-wild-do-table=foo%.bar% replicates only updates that use a table where the database name starts with foo and the table name starts with bar