sql - 如何通过SQL查询设置变量？(How to set variable from a SQL query?)

Question

I'm trying to set a variable from a SQL query: (我正在尝试通过SQL查询设置变量：)

declare @ModelID uniqueidentifer

Select @ModelID = select modelid from models
where areaid = 'South Coast'

Obviously I'm not doing this right as it doesn't work. (显然，我没有这样做，因为它不起作用。) Can somebody suggest a solution? (有人可以提出解决方案吗？)

Thanks! (谢谢！)

  ask by Mr Cricket translate from so

Answer 1

Using SELECT: (使用SELECT：)

SELECT @ModelID = m.modelid 
  FROM MODELS m
 WHERE m.areaid = 'South Coast'

Using SET: (使用SET：)

SET @ModelID = (SELECT m.modelid 
                  FROM MODELS m
                 WHERE m.areaid = 'South Coast')

See this question for the difference between using SELECT and SET in TSQL . (有关在TSQL中使用SELECT和SET之间的区别，请参见此问题 。)

Warning (警告)

If this select statement returns multiple values (bad to begin with): (如果此select语句返回多个值 （开头不正确）：)

• When using SELECT , the variable is assigned the last value that is returned (as womp said), without any error or warning (this may cause logic bugs) (使用SELECT ，将为变量分配返回的最后一个值（如womp所说），而不会出现任何错误或警告（这可能会导致逻辑错误）)
• When using SET , an error will occur (使用SET ，将发生错误)