Question

如果我发现某些用户存在这样的参数，我希望得到1否则为0.将来我将不得不添加更多的块。但它现在似乎不起作用。我做错了什么？

 SELECT CAST(CASE WHEN EXISTS(SELECT 1
                              FROM Customers
                              WHERE Country = 'France' AND PostalCode%2 = 0)
                              OR (WHERE Country = 'Germany' AND PostalCode%2 = 0))
                              ) 
                  THEN 1 
                  ELSE 0 
              END AS BIT)

Answer 1

您需要两个单独的exists：

SELECT CAST(CASE WHEN EXISTS (SELECT 1
                              FROM Customers
                              WHERE Country = 'France' AND PostalCode%2 = 0
                             )
                 THEN 1
                 WHEN EXISTS (SELECT 1
                              FROM Customers
                              WHERE Country = 'Germany' AND PostalCode%2 = 0
                             )
                 THEN 1
                 ELSE 0
            END AS BIT)

实际上，我把它分成两个单独的THEN条款。这几乎等同于使用OR，但由于逻辑位于CASE内，THEN似乎更自然。（不同之处在于优化器可以选择重新排列OR条件，但THEN条件以词法顺序执行。）

如果您的陈述实际上很简单，您可以将它们组合为：

SELECT CAST(CASE WHEN EXISTS (SELECT 1
                              FROM Customers
                              WHERE Country IN ('France', 'Germany') AND PostalCode%2 = 0
                             )
                 THEN 1
                 ELSE 0
            END AS BIT)

Answer 2

在我看来，您只是遇到了包围问题：

This is a 
very long 
sentence t
hat needs 
to be chun
ked up

根据戈登的假设，SELECT CAST( CASE WHEN EXISTS( SELECT 1 FROM Customers WHERE (Country = 'France' AND PostalCode%2 = 0) OR (Country = 'Germany' AND PostalCode%2 = 0) ) THEN 1 ELSE 0 END AS BIT)对于所有经过测试的“条件”（你还没有说过），你也可以将其缩短为：

PostalCode%2 = 0

在SQL中返回1或0，具体取决于多个语句

2 个答案: