我試圖獲取存在的子記錄數量的類別列表。如果類別沒有記錄,它應該返回NULL或0,但是我的查詢返回具有子記錄的類別看起來像跳過沒有子記錄的類別。 ...會非常感謝幫助。mysql左連接不返回空行
這裏是我的代碼:
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
這裏的兩個表:
你可以檢查:'選擇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