如何更新空列？

使用Access 2003如何更新空列？

兩個表，Tmp_cardevent1，tmp_cardevent3

查詢

SELECT AllPossibleCardEvents.PersonId, AllPossibleCardEvents.CardEventDate, Actual.Intime FROM ((SELECT p.PersonId, AllDates.CardEventDate FROM (SELECT DISTINCT CardEventDate FROM TMP_Cardevent3) AllDates, Tmp_cardevent1 p) AllPossibleCardEvents LEFT OUTER JOIN TMP_cardevent3 Actual ON AllPossibleCardEvents.PersonId = Actual.PersonId AND AllPossibleCardEvents.CardEventDate = Actual.CardEventDate)

輸出。

PERSONID CardEventDate Intime 
3156 05/08/2008 
3335 05/08/2008 
3405 05/08/2008 20:58:58 
3406 05/08/2008 
3410 05/08/2008 
3422 05/08/2008 
3424 05/08/2008 
3441 05/08/2008 
3447 05/08/2008 
3461 05/08/2008 
48 05/08/2008 
484 05/08/2008 
5 05/08/2008 
5008 05/08/2008 20:01:45

...等，

對於空白銀泰專欄中，我要顯示這樣的 '-----'

試圖查詢

SELECT PERSONID, CARDEVENTDATE, INTIME FROM 
(SELECT AllPossibleCardEvents.PersonId, AllPossibleCardEvents.CardEventDate, (iif(Actual.Intime=’’, ‘-----‘,Actual.Intime) as Intime FROM ((SELECT p.PersonId, AllDates.CardEventDate FROM (SELECT DISTINCT CardEventDate FROM TMP_Cardevent3) AllDates, Tmp_cardevent1 p) AllPossibleCardEvents LEFT OUTER JOIN TMP_cardevent3 Actual ON AllPossibleCardEvents.PersonId = Actual.PersonId AND AllPossibleCardEvents.CardEventDate = Actual.CardEventDate))

但我不能能更新空列，該結構是否可用於銀泰專欄

預期輸出

PERSONID CardEventDate Intime 
3156 05/08/2008 ----- 
3335 05/08/2008 ----- 
3405 05/08/2008 20:58:58 
3406 05/08/2008 ----- 
3410 05/08/2008 ----- 
3422 05/08/2008 ----- 
3424 05/08/2008 ----- 
3441 05/08/2008 ----- 
3447 05/08/2008 ----- 
3461 05/08/2008 ----- 
48 05/08/2008 ----- 
484 05/08/2008 ----- 
5 05/08/2008 ----- 
5008 05/08/2008 20:01:45

如何對這個空列進行查詢？

來源

2009-08-06 Gopal

請騰出更多的精力到一個更可讀的狀態 – AnthonyWJones 2009-08-06 10:44:15

您可以使用IsNull內置功能。

SELECT 
    PERSONID, 
    CARDEVENTDATE, 
    INTIME 
FROM 
    (SELECT 
     AllPossibleCardEvents.PersonId, 
     AllPossibleCardEvents.CardEventDate, 
     (iif(iif(IsNull(Actual.Intime), '', Actual.Intime)='', '-----', Actual.Intime) as Intime 
    FROM ((SELECT 
     p.PersonId, 
     AllDates.CardEventDate FROM 
     (SELECT DISTINCT 
      CardEventDate FROM TMP_Cardevent3) AllDates, 
      Tmp_cardevent1 p) AllPossibleCardEvents 
     LEFT OUTER JOIN TMP_cardevent3 Actual 
     ON AllPossibleCardEvents.PersonId = Actual.PersonId AND 
     AllPossibleCardEvents.CardEventDate = Actual.CardEventDate))

來源

2009-08-06 10:43:09 Kirtan

格式化你的代碼，爲什麼不乾脆：IIF（Actual.Intime IS NULL，「-----」，Actual.Intime）作爲銀泰;另外，考慮到列將被強制爲NVARCHAR（255），對DATETIME進行明確格式化不是一個好主意，例如作爲銀泰的iif（Actual.Intime IS NULL，'-----'，FORMAT $（Actual.Intime，'hh：nn：ss'））; ？ – onedaywhen 2009-08-06 14:37:00

這隻會將NULL值轉換爲破折號，他還想將空字符串轉換爲破折號。順便說一句，我們也可以使用'IS NULL'檢查。 – Kirtan 2009-08-07 04:24:35

爲什麼不是Nz？ Nz（Actual.Intime，「」）或更好：修剪（Actual.Intime＆「」）=「」 – Fionnuala 2009-08-07 09:15:22

如何更新空列？

回答

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