mysql - MySQL 中的三个表连接计数

Question

我这里有个问题；当我查询时:

SELECT product.*,product_description.*,COUNT(product_image.*) 
FROM " . DB_PREFIX . "product  
INNER JOIN product_description ON product.product_id = product_description.product_id 
INNER JOIN product_image ON product.product_id = product_image.product_id 
ORDER BY product.date_modified DESC

我想为表 product_image 选择 3 表 n 1 计数，但出现此错误:

Notice: Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ') FROM product INNER JOIN product_description ON product.product_id = product_' at line 1 Error No: 1064 SELECT product.,product_description.,COUNT(product_image.) FROM product INNER JOIN product_description ON product.product_id = product_description.product_id INNER JOIN product_image ON product.product_id = product_image.product_id ORDER BY product.date_modified DESC

Answer 1

您不应该像这样使用COUNT 函数。 COUNT(TableName.*) 连接表时。您需要像这样使用它的任何列 COUNT(TableName.ColumnName)。

例如COUNT(product_image.ID)

See this SQLFiddle