Question

我尝试同时执行这三个查询，但是我只能分别执行每个查询。

UPDATE post SET category=CONCAT(category,',2') WHERE id = 1 AND category LIKE '%5%' AND category LIKE '%1%'; 
UPDATE post SET category=CONCAT(category,',4') WHERE id = 1 AND category LIKE '%5%' AND category LIKE '%2%'; 
UPDATE post SET category=CONCAT(category,',6') WHERE id = 1 AND category LIKE '%5%' AND category LIKE '%3%';

我不明白如何正确编写查询：

UPDATE post SET
category = CONCAT(category,',2')IF(id 1 AND category LIKE '%1%'),
category = CONCAT(category,',4')IF(id 1 AND category LIKE '%2%'),
category = CONCAT(category,',6')IF(id 1 AND category LIKE '%3%')
WHERE id 1 AND category LIKE '%5%';

Answer 1

您可以使用CASE语句完成当前任务

UPDATE post 
SET category = CASE  
  WHEN category LIKE '%1%' THEN CONCAT(category,',1')
  WHEN category LIKE '%2%' THEN CONCAT(category,',2')
  WHEN category LIKE '%3%' THEN CONCAT(category,',3')
  ELSE category
END 
WHERE id = 1 AND category LIKE '%5%'

但是此任务意味着您数据库的结构是错误的，需要进行规范化。您应该阅读第一种规范化表格

Answer 2

在IF函数中使用条件分支：

UPDATE post 
SET category = IF(category LIKE '%1%', 
                  CONCAT(category,',2'), 
                  IF(category LIKE '%2%', 
                     CONCAT(category,',4'), 
                     IF(category LIKE '%3%', 
                        CONCAT(category,',6'), 
                        category
                       )
                    )
                 )
WHERE id = 1 
  AND category LIKE '%5%'

在一个查询中更新具有不同条件的一行

2 个答案: