【MySQL】【故障】平常小问题记录

时间 2020-04-26

标签 MySQL 故障平常问题记录栏目 MySQL 繁體版

原文原文链接

删除记录时提示须要SELECT 权限

(1143, "SELECT command denied to user 'test_delete'@'localhost' for column 'id' in table 'agent_info'")

参考

https://stackoverflow.com/questions/22580529/mysql-duplicate-entry-error-when-trying-to-add-new-columnphp

修改表增长行时提示主键有重复记录

其实没有，是由于5.6开始支持在线修改表结构。向新表追加dml log时会出现空洞重复java

参考

https://bugs.mysql.com/bug.php?id=76895mysql

WHERE columnX=NULL是否规范？

不规范
应使用 WHERE columnX IS NULLsql

MySQL中WHERE columnX=NULL等效WHERE columnX IS NULLbash

SQL92规范中中WHERE columnX=NULL永远不成立ide

参考

https://stackoverflow.com/questions/2747279/something-about-ansi-nullscode

You can't specify target table for update in FROM clause

参考

https://stackoverflow.com/questions/4429319/you-cant-specify-target-table-for-update-in-from-clauseci

获取准确的页面记录数量总计

SELECT s.*,t.count 
FROM 
    instance_summary AS s
JOIN
    (SELECT COUNT(*) AS `count` FROM instance_summary) AS t

INSERT ON DUPLICATE KEY UPDATE 死锁

在5.7版本上比较常见
解决办法: 先更新,后插入get

int affectRows = update(sql)
if (affectRows ==0 )
{ 
 // 某些状况下可能要先检查行记录是否存在,而后insert。经过主动采样的方式减少异常发生
    insert(sql) 
}

参考

The following notes will be helpful for you,

mysql_affected_rows() returns

+0: a row wasn't updated or inserted (likely because the row already existed, but no field values were actually changed during the UPDATE).

+1: a row was inserted

+2: a row was updated

-1: in case of error.

https://stackoverflow.com/questions/9397291/mysql-affected-rows-returns-0-for-update-statement-even-when-an-update-actuallit