Total number of MySQL statistics, used and unused

MySQL： surface storage_room,storage_rack

room:

rack:

sql Method 1 :

// After testing , This article sql Of count(*) The statistics are not accurate , If you need statistics, you need to write it yourself , I can test it

SELECT
            a.*,b.id,b.storage_room_id,b.status,count(*),count(CASE WHEN status='2' THEN 0 END) qy,count(CASE WHEN status='3' THEN 0 END) wqy
        FROM
            wd_storage_room a
                LEFT JOIN wd_storage_rack b ON a.id = b.storage_room_id
// This article sql To sum up to the top sql And it's written       
SELECT count(*),count(CASE WHEN status='2' THEN 0 END) qy,count(CASE WHEN status='3' THEN 0 END) wqy FROM wd_storage_rack

sql Method 2 ：// This item is on jeecgboot Under the framework of sql

SELECT
    a.*,
    (SELECT COUNT(ac.id) FROM wd_storage_rack ac WHERE ac.storage_room_id = a.id) AS storageRackAllNum,
    (SELECT COUNT(ac.id) FROM wd_storage_rack ac WHERE ac.storage_room_id = a.id AND ac.`status` = 2) AS storageRackUseNum,
    (SELECT COUNT(ac.id) FROM wd_storage_rack ac WHERE ac.storage_room_id = a.id AND ac.`status` = 3) AS storageRackUnUseNum
FROM
    wd_storage_room a
ORDER BY create_time DESC

Newly changed sql

 

SELECT
    a.id,a.storage_rack_id,a.code,a.title,a.site,a.enable,
    count(distinct b.id) as storageRackAllNum,
    count(distinct CASE WHEN b.status='1' THEN 0 END) as storageRackUseNum,
    count(distinct CASE WHEN b.status='2' THEN 0 END) as storageRackUnUseNum
FROM
((SELECT * FROM wd_storage_room ) a
left join (SELECT * FROM wd_storage_rack ) b
on  FIND_IN_SET(b.id, a.storage_rack_id))
<if test="storageRoom.title != null and storageRoom.title != ''">
    where
    a.title=${storageRoom.title}
</if>
group by a.id