说我有这三个表:
Table: Baskets
id | name
1 Sale
2 Premium
3 Standard
4 Expired
Table: Fruit
id | name | basketid
1 Apples 1
2 Oranges 2
3 Grapes 3
4 Apples 2
5 Apples 4
Table: Veggies
id | name | basketid
1 Carrots 1
2 Peas 2
3 Asparagus 1
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看起来后两个表应该只是一个称为Produce的表,但是在实际情况下,有充分的理由使它们成为不同的表。我需要编写一个联接,如果购物篮的水果表或蔬菜表中有行,则返回行。我以为我可以通过两个左连接来完成此操作,如下所示:
Select Baskets.*, fruit.name as fruit,
veggies.name as veggies
from Baskets
left join Fruit on Baskets.id = Fruit.basketid
left join veggies on Baskets.id = Veggies.basketid
where Baskets.id = …Run Code Online (Sandbox Code Playgroud)