SQL QUERY选择所有值 [英] SQL QUERY TO SELECT ALL VALUES

问题描述

我将c＃中的用户值传递给sql

它可能为null或任何值。

例如; @city =''chennai''或''''



我的查询：从AdmissionTbl中选择FirstName，其中City = @ city

if @ city =''''那么它应该只检索所有记录''chennai''记录。

它仅适用于选定的（''chennai''）值。如果它为null则它不会检索任何记录。

如何在sql中查询？

im passing user value in c# to sql
it may be null or any value.
eg; @city=''chennai'' or ''''

My query : select FirstName from AdmissionTbl where City=@city
if @city='''' then it should retrieve all records else only ''chennai'' records.
it works only for selected(''chennai'') value. if it is null it doesn''t retrieve any records.
how to query in sql?

推荐答案

SELECT FirstName FROM AdmissionTbl (NOLOCK) WHERE (City=@City OR @City IS NULL OR @City = '')

由于您在前端有C＃代码，只需检查您是否需要通过一个城市，

如果你不不必，不要将参数添加到代码中，也可以跳过 where 子句。

Since you have C# code in the front end, simply check if you need to pass in a city,
If you don''t have to, don''t add the parameter to the code and also skip the where clause.

SELECT FirstName from AdmissionTbl where City=@city OR CITY IS NULL ;

SELECT CASE WHEN FirstName  IS NULL THEN 'NO VALUE' ELSE  FirstName   where City=@city OR CITY IS NULL ;

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