mysql中的if子句

Question

我想要一個mysql中if子句的簡單示例。我不想考慮別的情況下，只有當第

Answer 1

例如：

SELECT *, 
     if (`date_last` IS NULL,prev_date,last_date) as date 
FROM `table_name` 
WHERE `id` = 2 
ORDER BY `date` DESC