Sql server 在函数中使用if、else

我使用nelow查询用于if，但出现错误

CREATE FUNCTION getStationCityCode
(
    @stationCode int
)
RETURNS bigint
AS BEGIN
    RETURN 
    (
          if((select cityCode from Station where code=@stationCode)!=0)
        select cityCode from Station where code=@stationCode
          else
             select 1 as cityCode
    )
END 

---

您需要使用

大小写

表达式

CREATE FUNCTION getStationCityCode
(
    @stationCode int
)
RETURNS bigint
AS BEGIN
    RETURN 
    (
        SELECT CASE WHEN cityCode!=0 THEN cityCode ELSE 1 END as cityCode
        FROM Station 
        WHERE code=@stationCode
    )
END