Question

我有一段SQL代码取自SQL Server下的ELMAH存储过程：

DELETE FROM [ELMAH_Error]
WHERE ErrorId NOT IN (SELECT TOP 100 ErrorId FROM ELMAH_Error ORDER BY TimeUtc DESC)

我现在迁移一个网站改为使用mysql，我不知道如何翻译这段代码。

我必须在这段代码之后添加翻译：

CREATE DEFINER=`b43638b86659eb`@`%` PROCEDURE `elmah_LogError`(
    IN ErrorId CHAR(36), 
    IN Application varchar(60), 
    IN Host VARCHAR(30), 
    IN Type VARCHAR(100), 
    IN Source VARCHAR(60), 
    IN Message VARCHAR(500), 
    IN User VARCHAR(50), 
    IN AllXml TEXT, 
    IN StatusCode INT(10), 
    IN TimeUtc DATETIME
)
    MODIFIES SQL DATA
BEGIN
    INSERT INTO `elmah_error` (
        `ErrorId`, 
        `Application`, 
        `Host`, 
        `Type`, 
        `Source`, 
        `Message`, 
        `User`, 
        `AllXml`, 
        `StatusCode`, 
        `TimeUtc`
    ) VALUES (
        ErrorId, 
        Application, 
        Host, 
        Type, 
        Source, 
        Message, 
        User, 
        AllXml, 
        StatusCode, 
        TimeUtc
    );
END

我尝试在END语句之前添加@Sick的响应，但是SQL Workbench（通过alter procedure命令）看不到它。

由于

Answer 1

等效的Sql Server TOP Mysql中的关键字是Limit，它应该在查询的末尾

DELETE FROM `ELMAH_Error`
WHERE ErrorId NOT IN (SELECT ErrorId 
                      FROM `ELMAH_Error`
                      ORDER BY TimeUtc DESC LIMIT 100)

Answer 2

MySQL在某些子查询中不支持$ gcc main.c phy.c frm.c $ ./a.out Main. PHY stuff. Running phy_cb. phy_cb, default implementation. BAD!!! <--- not expected! FRM stuff. Running frm_cb frm_cb, APP implementation. GOOD。如果是这种情况，那么使用显式连接：

limit

编辑：

上述代码假定DELETE e FROM ELMAH_Error e LEFT JOIN (SELECT ErrorId FROM ELMAH_Error ORDER BY TimeUtc DESC LIMIT 100 ) ee ON ee.ErrorId = e.ErrorId WHERE ee.ErrorId IS NULL;在表格中是唯一的，并且没有ErrorId值。如果不是这样，那么查询将不起作用。（注意：假设一个名为Id的列是唯一的而不是null似乎是非常合理的。）

NULL

Answer 3

如果表格非常大，那么截断通常比MySQL中的删除要快得多。类似的东西：

lock tables ELMAH_Error write;
create temporary table cpy_ELMAH_Error 
   select * from ELMAH_Error order by TimeUtc DESC LIMIT 100;
truncate table ELMAH_Error;
insert into  ELMAH_Error select * from cpy_ELMAH_Error;
drop table cpy_ELMAH_Error;
unlock tables;

Answer 4

There is one more somewhat simpler way if you are interested:

set @N=0;
delete from ELMAH_Error where (@N:=@N+1) > 101 order by TimeUtc DESC;

如何在mysql中编写这个特定的查询？

4 个答案: