select语句中的MYSQL Case用于检查null [英] MYSQL Case in select statement for checking null

问题描述

在MySQL查询中，如果我通过了:

in MySQL query if I pass :

  case guides.Gud_Publish_Date 
     when null then "Unscheduled" 
     else "Forth Coming Titles" 
  end

然后，即使Gud_Publish_Date也具有值，它都考虑全部为空.完整的SQL语句是

then it is considering all is null even the Gud_Publish_Date has value also. the full SQL statement is

SELECT guides.Gud_Id
    , guides.Gud_Image
    , guides.Gud_SubEditor
    , guides.Gud_Reprint_Status
    , guides.Gud_Publish_Date
    , guides.Gud_Img_Chk
    , guides.Gud_Published
    , guides.Gud_View
    , (
        CASE guides.Gud_Publish_Date
            WHEN NULL
                THEN "Unscheduled"
            ELSE "Forth Coming Titles"
            END
        ) AS Schedules
FROM guides

有人可以帮助我吗?预先感谢

Can anybody help me? Thanks in advance

推荐答案

尝试使用IF

SELECT guides.Gud_Id
    , guides.Gud_Image
    , guides.Gud_SubEditor
    , guides.Gud_Reprint_Status
    , guides.Gud_Publish_Date
    , guides.Gud_Img_Chk
    , guides.Gud_Published
    , guides.Gud_View
    , IF(guides.Gud_Publish_Date IS NULL,'Unscheduled','Forth Coming Titles') 
             AS Schedules
FROM guides

或者如果您真的想要CASE

SELECT guides.Gud_Id
    , guides.Gud_Image
    , guides.Gud_SubEditor
    , guides.Gud_Reprint_Status
    , guides.Gud_Publish_Date
    , guides.Gud_Img_Chk
    , guides.Gud_Published
    , guides.Gud_View
    , (
        CASE 
            WHEN guides.Gud_Publish_Date IS NULL
            THEN 'Unscheduled'
            ELSE 'Forth Coming Titles'
        END
      ) AS Schedules
FROM guides

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