我试图获取存在的子记录数量的类别列表。如果类别没有记录,它应该返回NULL或0,但是我的查询返回具有子记录的类别看起来像跳过没有子记录的类别。 ...会非常感谢帮助。mysql左连接不返回空行
这里是我的代码:
SELECT
t_gal.f_sub_category_id,
t_sub_cat.f_sub_cat_name,
t_gal.f_image_thumb, (
SELECT COUNT(*)
FROM t_gallery
WHERE f_sub_category_id = t_gal.f_sub_category_id)
AS f_image_total
FROM t_gallery t_gal
LEFT JOIN t_sub_category t_sub_cat ON t_sub_cat.r_id = t_gal.f_sub_category_id
GROUP BY t_sub_cat.r_id
ORDER BY t_gal.f_added_on DESC, t_gal.r_id DESC
这里的两个表:
你可以检查:'选择tg.f_sub_category_id, tsc.f_sub_cat_name, tg.f_image_thumb, COUNT(*)f_image_total FROM t_gallery TG LEFT JOIN t_sub_category tsc ON tsc.r_id = tg.f_sub_category_id GROUP BY tg.f_sub_category_id,tg.r_id ORDER BY tsc.f_added_on DESC,tg.r_id DESC;'? – SparKot 2013-03-05 13:26:06