mysql - MySQL中的三个表连接计数

Question

我这里有问题；当我进行查询时：

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 个表 n 1 个计数，但出现此错误：

注意：错误：您的 SQL 语法有错误；检查与您的 MySQL 服务器版本相对应的手册，以在第 1 行错误号：1064 SELECT product. ，产品描述。,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

你不应该使用COUNT这样的功能。COUNT(TableName.*)在加入表格时。你需要使用它的任何一个这样的列COUNT(TableName.ColumnName)。

例如COUNT(product_image.ID)

看到这个 SQLFiddle

Answer 2

使用派生查询进行计数

SELECT 
    product.*,
    product_description.*,
    pi.Count as T_Count
FROM " . DB_PREFIX . "product  
INNER JOIN product_description ON product.product_id = product_description.product_id 
INNER JOIN (SELECT product_id , count(*) as Count FROM product_image) as pi ON product.product_id = pi.product_id 
ORDER BY product.date_modified DESC

Answer 3

尝试这个：：

SELECT 
product.*,
product_description.*,
COUNT(1) 
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