在我的 mysql 查询中,如果元素存在,我将对其进行计数。如果产品存在,它返回实际计数,但如果没有产品,则返回 NULL
。如果值为 null,我如何返回 0
?我找到了 One , Two与此问题相关的线程。但它们都没有帮助。
我的查询是
SELECT
COUNT(*) AS num
FROM
table1 AS t1
JOIN table2 AS t2 ON t2.id = t1.id_fk
JOIN table3 AS t3 ON t3.id = t2.t3_id_fk
JOIN table4 AS t4 ON t4.id = t2.t4_id_fk
JOIN table 5 AS t5 ON t5.t2_id_fk = t2_id
WHERE pd.product_url = 'sample_product'
AND mcd.main_category_url = 'sample_category'
AND scd.sub_category_url = 'sample_sub_category'
AND mpd.merchant_prod_status = 'active'
AND pd.product_status = 'active'
AND mcd.main_category_status = 'active'
AND scd.sub_category_status = 'active'
GROUP BY t1.id
我还尝试了 IFNULL(count(*), 0)
。它也给 NULL
请帮助我...任何帮助将不胜感激。提前谢谢你
最佳答案
你应该封装它:
SELECT IFNULL(num,0)
FROM ( SELECT COUNT(*) AS num
FROM table1 AS t1
JOIN table2 AS t2 ON t2.id = t1.id_fk
JOIN table3 AS t3 ON t3.id = t2.t3_id_fk
JOIN table4 AS t4 ON t4.id = t2.t4_id_fk
JOIN table 5 AS t5 ON t5.t2_id_fk = t2_id
WHERE pd.product_url = 'sample_product'
AND mcd.main_category_url = 'sample_category'
AND scd.sub_category_url = 'sample_sub_category'
AND mpd.merchant_prod_status = 'active'
AND pd.product_status = 'active'
AND mcd.main_category_status = 'active'
AND scd.sub_category_status = 'active'
GROUP BY t1.id
) s
关于mysql - 防止 count() 在 mysql 中返回 "NULL",我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/24800007/