MySql-将ALIAS用于​​多列 [英] MySql - use of ALIAS for multiple columns

问题描述

我看到了以下代码：

  SELECT 
 u.ID，u.username，u.active， u.email，u.admin，u.banned，
 u.name AS组成员身份
来自用户u 
 WHERE u.ID = {$ uid} 
  

，并且想知道有关别名多列的官方文档在哪里。 W3schools（不是最佳来源）是我通过以下方式找到文档的唯一地方：

  SELECT column_name（s ）FROM table_name AS alias_name; 
  

http://www.w3schools.com/sql/sql_alias.asp

我希望收到指向官方文档的链接，所以我可以查看一下。

解决方案

您不能对多个列使用相同的别名，但可以将值连接起来并给结果别名：

  SELECT 
 u.ID，u.username，u.active，u.email，u .admin，u.banned，
 u.name + u.username作为组成员
 FROM用户u 
  

如果这是您想要的，请在此处中查看如何处理空值。 p>

I saw the following code:

SELECT 
    u.ID, u.username, u.active, u.email, u.admin, u.banned, 
    u.name AS groupmemberships 
FROM users u 
WHERE u.ID={$uid}

and was wondering where the official documentation about aliasing multiple columns was. W3schools (not the best source) as the only place where I found "documentation" in the following way:

SELECT column_name(s) FROM table_name AS alias_name;

http://www.w3schools.com/sql/sql_alias.asp

I would appreciate a link to official documentation so I can look it over.

解决方案

You can't use the same alias for multiple columns, but you can concatenate values and give the result an alias:

SELECT 
  u.ID, u.username, u.active, u.email, u.admin, u.banned, 
  u.name + u.username AS groupmemberships 
FROM users u 

If this is what you want, then check here for how to deal with null values.

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