我可以写一个基于属性值的SQL语句吗？ [英] Can I write one SQL statement based on a property value?

问题描述

我想知道我是否可以编写一个SQL语句，或者如果我将使用应用程序的控制流编写许多不同的SQL语句。

I was wondering if I could write one SQL statement or if I will have to write many different SQL statements using the control flow of the application.

基本上，我有一个名为学生的表，将有一个列性（M，F）。

Essentially, I have a table called Students that will have a column sex(M,F).

我也有一个称为Divisions的表，它将有一个名为sex（null，M，F）的列。如果值为null，我要检索所有学生，包括男性和女性。

I also have a table called Divisions that will have a column named sex(null, M, F). If the value is null, I want to retrieve all students, both male and female.

我知道我可以写两个不同的语句来完成这项工作。但是，我有其他列将工作方式相同，我想知道是否可以写一个语句，而不是10。

I know I can write two different statements to get this job done. But, I have other columns that will work the same way and I was wondering if there is a way I could write one statement rather then 10.

推荐答案

是的，只要确保您的连接条件满足您的要求：
这样的东西（未测试）

Yes, just make sure your join condition does what you ask: Something like this (untested)

select * from students s left outer join division d on (s.sex=d.sex or d.sex is null)

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