我需要 WHERE 子句来更改遇到 NULL 时它正在评估的列。例如，我正在尝试做这样的事情：
SELECT *
FROM customer c
WHERE CASE WHEN c.cust_id_1(@variable) IS NOT NULL THEN c.cust_id_1 = @variable
ELSE CASE WHEN c.cust_id_2(@variable) IS NOT NULL THEN c.cust_id_2 = @variable
ELSE c.cust_id_3 = @variable这样的事情可能吗？ 3 个 cust_id 之一不会为 NULL。
回答1
这似乎不是最佳的 table 设计，但不是您所追求的简单 COALESCE 吗？
WHERE @variable = COALESCE(cust_id_1, cust_id_2, cust_id_3);回答2
您不需要 CASE 表达式，您只需要逻辑运算符
SELECT *
FROM customer c
WHERE
(c.cust_id_1 IS NOT NULL AND c.cust_id_1 = @variable)
OR
(c.cust_id_2 IS NOT NULL AND c.cust_id_2 = @variable)
OR
(c.cust_id_3 IS NOT NULL AND c.cust_id_3 = @variable)