SQL：如何在查詢中使用大小寫和強制轉換？

Question

我想將VARCHAR轉換爲INT，但在我的表中我有一些值'???'那麼SQL Server啓動這個表達式：

Conversion failed when converting the varchar value '????' to data type int. 
Severity 16 

我可以將此'???'爲NULL，這是沒有問題的，但怎麼做？

我試圖做這樣的事情：

INSERT INTO labbd11..movie(title, year) 
SELECT movies.title, 
     CASE movies.mvyear IS '????' THEN NULL ELSE CAST (movies.mvyear AS INT) 
FROM disciplinabd..movies 

但沒有任何工程..

任何想法的傢伙？

Answer 1

你可能只是想解決這個一般和處理任何非int值以同樣的方式

INSERT INTO labbd11..movie(title, year) 
    SELECT movies.title, 
      CASE WHEN IsNumeric(movies.mvyear+ '.0e0') <> 1 THEN NULL 
       ELSE CAST (movies.mvyear AS INT) END 
     FROM disciplinabd..movies 

看到這個question

Answer 2

我相信你會想是

INSERT INTO labbd11..movie(title, year) 
    SELECT movies.title, 
     CAST(CASE movies.mvyear 
        WHEN '????' THEN NULL 
        ELSE movies.mvyear 
       END AS INT) 
    FROM disciplinabd..movies 

你希望你的CASE語句返回VARCHAR（無論是MVYEAR或NULL），然後你想要的內容投射到對案件的結果進行操作。

Answer 3

INSERT INTO labbd11..movie(title, year) 
    SELECT movies.title, 
      CASE WHEN movies.mvyear = '????' THEN NULL 
       ELSE CAST (movies.mvyear AS INT) END 
     FROM disciplinabd..movies 

Answer 4

INSERT INTO labbd11..movie(title, year) 
    SELECT 
     movies.title, 
     CAST(CASE WHEN movies.mvyear = '????' THEN NULL ELSE movies.mvyear END AS INT) 
    FROM 
     disciplinabd..movies 

Answer 5

你也可以使用：

CAST(NULLIF(movies.mvyear,'????') AS INT)