Question

我需要所有Library_ID作为是或否返回。它们是1,2或3，所以我需要将1,2或3的所有内容更改为“是”，将所有其他内容更改为“否”。以下是我到目前为止的发言：

SELECT DISTINCT 
    Title, Publisher, Release_Date, ISBN, l.Library_ID
FROM  
    Catalog_Item c
INNER JOIN 
    Book b ON c.Catalog_Item_ID = b.Catalog_Item_ID
INNER JOIN 
    Physical_Item p ON c.Catalog_Item_ID = p.Catalog_Item_ID
INNER JOIN 
    Branch br ON p.Branch_ID = br.BRranch_ID
INNER JOIN 
    Library l ON br.Library_ID = l.Library_ID
ORDER BY 
    Title;

现在我被卡住了。

Answer 1

这么简单吗？

SELECT DISTINCT
    Title, Publisher, Release_Date, ISBN,
    case when l.Library_ID in (1,2,3) then 'Yes' else 'No' end as Library_ID
From ...

Answer 2

尝试以下 CASE 表达式： -

SELECT DISTINCT Title, Publisher, Release_Date, ISBN, l.Library_ID, CASE WHEN l.Library_ID IN (1,2,3) THEN 'YES' ELSE 'NO' END AS "YES_OR_NO" FROM Catalog_Item c INNER JOIN Book b ON c.Catalog_Item_ID = b.Catalog_Item_ID INNER JOIN Physical_Item p ON c.Catalog_Item_ID = p.Catalog_Item_ID INNER JOIN Branch br ON p.Branch_ID = br.BRranch_ID INNER JOIN Library l ON br.Library_ID = l.Library_ID ORDER BY Title;

使用join语句创建case表达式;神谕

2 个答案: