如何在SQL Server中串联 [英] How to concatenate in SQL Server

问题描述

我的数据库没有特定的列，因此我通过switch在查询中创建了一个列。我需要将该列与数据库中的另一列连接起来：

My database doesn't have a specific column so I created a column in my query by switch. What I need is to concatenate this column with another column in the database:

select 
    certificateDuration ,
   'DurationType' = case
                      when certificateDurationType = 0 then 'Day' 
                      when certificateDurationType = 1 then 'Month'
                      when certificateDurationType = 2 then 'Year'
                    end
from 
    Scientific_Certification

推荐答案

在SQL中连接字符串服务器上，您只需使用 +运算符。

注意，如果子字符串之一为null，则整个串联的字符串也将变为null。因此，即使一个子字符串为空，也需要结果，请使用 COALESCE 。

To concatenate strings in SQL Server you can simply use the + operator.
Note that if one of the substrings is null then the entire concatenated string will become null as well. therefor, use COALESCE if you need a result even if one substring is null.

select certificateDuration,
       ' DurationType = '+ 
       COALESCE(case
                     when certificateDurationType = 0 then 'Day' 
                     when certificateDurationType = 1 then 'Month'
                     when certificateDurationType = 2 then 'Year'
                     end, '') As DurationType 
from Scientific_Certification

注意：我对您的case子句使用了合并，因为您没有默认行为（由 else 指定）。这意味着如果 certificateDurationType 不为0、1或2，则case语句将返回 null 。

Note: I've used coalesce on your case clause since you have no default behavior (specified by else). this means that if certificateDurationType is not 0, 1 or 2 the case statement will return null.

这篇关于如何在SQL Server中串联的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！