SQL if语句

Question

我希望能写下来：

IF PROV_ID = PROVIDER NOT ON FILE or blank then use BILLING_PROV 
ELSE USE PROV_ID

Billing_prov是列名，所以我想返回该值。

Answer 1

SELECT
 CASE WHEN (PROV_ID = [PROVIDER NOT ON FILE or blank])
      THEN BILLING_PROV 
      ELSE PROV_ID
      END
FROM
 ...

Answer 2

我假设“不存档或空白”表示空

SELECT COALESCE(PROV_ID, BILLING_PROV) as Whatever
FROM ...