如何在Oracle的where子句中使用IF THEN ELSE語句？

Question

我很有趣，我該如何在Oracle的where子句中使用if-then-else語句或任何控制結構。我想用爲：

• 時pcustomer_id IS NULL然後WHERE c.customer_id IS NULL
• 當pcustomer_id IS NOT NULL然後c.customer_id = pcustomer_id。

我該怎麼辦？

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

你需要他們捆綁

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

使用布爾表達式：

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

如果我理解正確的話你只是想返回所有值時，c.customer_id = pcustomer_id包括null股權。所以：

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

您只需要選擇在您的真實數據中不會出現的數字。