如何从不同的条件中获取多个值，就像WP Meta Query一样？

Question

META TABLE ==
meta_id | post_id | meta_key | meta_value
1       | 101     | quantity | 8
2       | 101     | price    | 100
3       | 102     | quantity | 7
4       | 102     | price    | 56
5       | 103     | quantity | 12
6       | 103     | price    | 256


POST TABLE ==
post_id | name      | about
101     | Pencil    | Luxurious pencil only for you
102     | Eraser    | All your mistakes, gone!
103     | Pen       | Unrivaled penmanship, stronger than sword.

如何进行查询以发布ID并获取帖子：名称，关于meta：value，price and quantity in one go？

所以结果将是

 101   | Pencil   | Luxurious pencil only for you              | 8   | 100
 102   | Eraser   | All your mistakes, gone!                   | 7   | 56
 103   | Pen      | Unrivaled penmanship, stronger than sword. | 12  | 256

谢谢

Answer 1

您必须两次join meta_table。如果数量或价格在给定post_id的meta_table中没有条目，请使用left join。

select p.post_id, p.name, p.about, m1.meta_value, m2.meta_value
from post_table p
join meta_table m1 on m1.post_id = p.post_id and m1.meta_key = 'quantity'
join meta_table m2 on m2.post_id = p.post_id and m2.meta_key = 'price'