如何在MySQL中進行查詢而不進行N + 1查詢

Question

我有2張桌子

users_table
id | first_name
1 | first name1
2 | first name2

addresses_table
id | user_id | address
1 | 1 | first address of user 1
2 | 1 | second address of user 1
3 | 2 | first address of user 2
4 | 2 | second address of user 2

我想要這樣的表結果，第一列是users_table first_name，第二列是每個用戶的愛好，用逗號分隔

<table>
<tr>
<td>first name1</td><td>first address of user 1, second address of user 1</td>
</tr>
<tr>
<td>first name2</td><td>first address of user 2, second address of user 2</td>
</tr>
</table>

如果我必須查詢，則必須select * from users_table然后select * from addresses_table where user_id = 1獲取每個用戶的地址，例如select * from addresses_table where user_id = 1 fromaddressstable，這不是很有效，可以使用ORM來防止，但是我想知道我們可以防止N使用SQL +1查詢

Answer 1

您可以使用以下查詢

從用戶表usrTable中選擇first_name，group_concat（address，'，'）作為地址usrTable.id = addTable.user_id上的組由first_name組成的addressstable addTable