如何在MySQL中使用带有INNER JOIN的SQL函数? [英] How to use a SQL Function with INNER JOIN in MySQL?

问题描述

我有一个函数"fnc_FindIssueId"，该函数接受一个对象ID并返回其分配的问题ID.

I have a function "fnc_FindIssueId" which accepts an object id and return its assigned issue Id.

当我使用纯select语句调用该函数时，它可以正常工作:

When I call the function using pure select statements, it works fine:

select fnc_FindIssueId(150083); // returns 1 as issueId for objectId of 150083
select fnc_FindIssueId(150072); // returns 2 as issueId for objectId of 150072

但是当我在内部联接中使用它时，它会陷入无休止的循环:

But when I use it within an Inner Join, it goes into a never-ending loop:

select so.id, si.id
from smart_objects as so 
       LEFT OUTER join smart_issues as si 
        on si.id = fnc_FindIssueId(so.id)
where so.id in (150083, 150072);

原因是什么，如何解决?

What's the reason and how to resolve it?

推荐答案

它不执行永无止境循环.

之所以这样做，是因为服务器执行FULL TABLE SCAN的速度非常慢.即使您已在si.id和so.id上定义一个索引，此条件si.id = fnc_FindIssueId(so.id)也不使用索引.

The reason for that is because the server performs FULL TABLE SCAN which is very slow. This condition si.id = fnc_FindIssueId(so.id) doesn't use an index even if you have define one on si.id and so.id.

最好的方法是:

• 更改表smart_objects
• assigned issue Id
的另一列
• 在新列上定义索引

• to alter the table smart_objects
• another column for the assigned issue Id
• define an index on the new column

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