Question

SELECT t.id_type, brand, model, countMod FROM types t  
    LEFT JOIN (
       SELECT p.id_type, brand, model, COUNT( model ) AS countMod 
           FROM products p  
           GROUP BY brand) p2 
    ON t.id_type = p2.id_type 
    WHERE t.id_type = "TCE" 
    ORDER BY brand

此查询工作正常，但我丢失了在每个品牌下分组的模型有没有办法列出并计算模型？
即brand1，model1，model2，model3，countMod = 3 - brand2，model1，model2，countMod = 2。
任何帮助将不胜感激。感谢

Answer 1

SELECT brand, GROUP_CONCAT(model) models, COUNT(model) AS countMod
FROM products
GROUP BY brand

Answer 2

试试这个::

SELECT 
t.id_type, 
brand,
GROUP_CONCAT(model SEPARATOR ',') as model, 
COUNT( model ) AS countMod 
FROM types t
LEFT JOIN products p  ON t.id_type = p.id_type
WHERE t.id_type = "TCE" 
GROUP BY brand
ORDER BY brand

Answer 3

推荐的方法是运行两个查询，一个用于数据，另一个用于COUNT()。

使用MySQL，你也可以使用SQL_CALC_FOUND_ROWS（主要是你有一个LIMIT子句），但是它的表现是有争议的，请参阅Which is fastest? SELECT SQL_CALC_FOUND_ROWS FROM `table`, or SELECT COUNT(*)。

select with count in sub select会因group by子句而产生不需要的结果

3 个答案: