[英]SQL LEFT JOIN using WHERE condition
我喜欢这张桌子:
categorizables
我也有没有任何外键的表products
和categories
。
我尝试创建这样的查询来计算每个类别的产品:
SELECT category_id, COUNT(categorizable_id), categories.title
FROM categorizables
LEFT JOIN categories ON categories.id = category_id
GROUP BY category_id
它有效,但是当我尝试添加WHERE
条件时,它不起作用:
SELECT category_id, COUNT(categorizable_id), categories.title
FROM categorizables
LEFT JOIN categories ON categories.id = category_id
WHERE categorizables.categorizable_type = "App\Models\Product"
GROUP BY category_id
如何正确添加WHERE
条件?
使用撇号而不是引号并转义反斜杠:
SELECT category_id, COUNT(categorizable_id), categories.title
FROM categorizables
LEFT JOIN categories ON categories.id = category_id
WHERE categorizables.categorizable_type = 'App\\Models\\Product'
GROUP BY category_id
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