如何在Oracle的where子句中使用IF THEN ELSE语句？

Question

我很有趣，我该如何在Oracle的where子句中使用if-then-else语句或任何控制结构。我想用为：

• 时pcustomer_id IS NULL然后WHERE c.customer_id IS NULL
• 当pcustomer_id IS NOT NULL然后c.customer_id = pcustomer_id。

我该怎么办？

SELECT * 
    FROM customer_inf c 
WHERE 
IF 
pcustomer_id IS NULL THEN (c.customer_id IS NULL) 
    ELSE (c.customer_id = pcustomer_id) END IF; 

Answer 1

你需要他们捆绑

where (
(pcustomer_id is null 
    and c.customer_id is null) 
or 
(pcustomer_id is not null 
    and c.customer_id = pcustomer_id) 
) 

Answer 2

使用布尔表达式：

SELECT * 
FROM customer_inf c 
WHERE (pcustomer_id IS NULL AND c.customer_id IS NULL) 
OR  (pcustomer_id IS NOT NULL AND cc.customer_id = pcustomer_id); 

Answer 3

如果我理解正确的话你只是想返回所有值时，c.customer_id = pcustomer_id包括null股权。所以：

select * from customer_inf c 
where nvl(pcustomer_id,'999999999999') = nvl(c.customer_id, '999999999999'); 

您只需要选择在您的真实数据中不会出现的数字。