mysql - 创建 View 并用单词替换空值

Question

我有一个 View ，我想用一个词更改列中的空值:other。

这是我目前尝试过的:

CREATE VIEW APB1 AS
  SELECT jos_jam.postcode, location_id, description, 
         category, apb.street, location, apb
  FROM jos_jam
  LEFT JOIN apb
  ON jos_jam.postcode=apb.postcode;
  FROM apb
  UPDATE APB1 SET apb = 'Other' where apb is null

那个没有正确替换值，我也试过:

CREATE VIEW APB1 AS
  SELECT jos_jam.postcode, location_id, description, 
         category, apb.street, location, apb
  FROM jos_jam
  LEFT JOIN apb
  ON jos_jam.postcode=apb.postcode;
  REPLACE(apb.apb, 'NULL') as 'Other'
  FROM apb

第二个查询出现以下错误:

#1064 - You have an error in your SQL syntax; check the manual that 
corresponds to your MySQL server version for the right syntax to use 
near 'FROM apb
UPDATE APBVolunteers4 SET apb = 'Other' where apb is null' at line 1 

此错误是什么意思，如何在 View 中用单词替换空值？

Answer 1

错误信息指的是第一个查询中的单词 FROM 或第二个查询中的单词 Replace 之前的分号。

您不能将更新语句放在创建 View 语句中。看起来您是在尝试更新数据库，而不是更新 View 中返回的内容。

此外，您的声明底部也不需要 From APB。

COALESCE() 运算符返回其参数列表中的第一个非空值。

我认为这应该可行:

CREATE VIEW APB1 AS
    SELECT jos_jam.postcode, location_id, description, category, apb.street, 
    location, COALESCE(apb, 'Other') as apb
FROM jos_jam
LEFT JOIN apb
   ON jos_jam.postcode=apb.postcode