将数据从 Mariadb table 插入另一个 table

Question

如果 main_table 对 email 的值为空，我似乎无法理解正确的语法以便将数据从一个 table 插入另一个 table。如果 main_table 电子邮件对于 id 是空的，那么我想从 secondary_table:

中插入 id 的 email

MariaDB> SELECT * FROM `main_table`;
+------+---------------------+----------------------------------+------+
| Id   | Email               | Other                            | More |
+------+---------------------+----------------------------------+------+
| 1    | user1@somewhere.com | blah                             | A    |
| 2    |                     | needs email from secondary_table | B    |
| 3    | user3@someplace.com | blah                             | C    |
+------+---------------------+----------------------------------+------+
3 rows in set (0.09 sec)

MariaDB> SELECT * FROM `secondary_table`;
+------+---------------------+-------+
| Id   | Email               | Info  |
+------+---------------------+-------+
| 1    | user1@somewhere.com | blah  |
| 1    |                     | blank |
| 2    | user2@something.com | blah  |
| 2    |                     | blank |
| 3    | user3@someplace.com | blah  |
| 3    |                     | blank |
+------+---------------------+-------+
6 rows in set (0.09 sec)

在此示例中，id 数字 2 在 main_table 中 email 为空。我正在尝试将 id 与 email 从 secondary_table 插入到 main_table。我试过：

INSERT INTO `main_table`
(`Email`)
VALUES
( SELECT `Email` FROM `secondary_table` WHERE `Id` IN
( SELECT `Id` FROM `main_table` WHERE `Email` == '') ) ;

一路上还有其他各种失败...也许这很简单，但我被卡住了！

Answer 1

查看您的示例，您似乎需要更新（通过加入）而不是插入
（假设 main_table 中的电子邮件字段为空）

update main_table
inner join secondary_table ON main_table.id = secondary_table.id 
set main_table.Email = secondary_table.Email               
where  main_table.Email is null     
and  secondary_table.email <> ''

或者假设 main_table 中的电子邮件字段是 =''

update main_table
inner join secondary_table ON main_table.id = secondary_table.id 
set main_table.Email = secondary_table.Email               
where  main_table.Email = ''
and secondary_table.email <> ''

将数据从 Mariadb table 插入另一个 table

Inserting data from Mariadb table into another table

mysql

mariadb