如何使用 MySQL JOIN 从第二个 table 中获取两个计数结果

Question

这里我有两个table，(trip_details & trip_member)，我的需求是基于tripId。我想获得员工在场人数和员工缺席人数。在 trip_member table 我存储了 tripId (foriegnkey), empId, empPresentStatus。 empPresentStatus= '1'表示他不在，empPresentStatus ='0'表示他在。

trip_details

tripId      allocationId       tripStatus

 1             1                  1
 2             1                  1

trip_member

id       tripId          empId       empPresentStatus

 1         1              G2E201        0
 2         1              G2E202        0
 3         1              G2E203        1
 4         2              G2E204        0
 5         2              G2E205        1

根据我的table结构，这次出差有多少员工在场，有多少员工缺席，我想统计一下。

I tried this

$mysql = mysql_query("SELECT a.tripId, a.cabNo, COUNT('b.*') AS absentCount FROM trip_details a LEFT JOIN trip_member b ON a.tripId = b.tripId WHERE b.empPresentStatus = '1' AND a.tripStatus ='1' GROUP BY a.tripId");
while ($row = mysql_fetch_assoc($mysql)) {
    $data[] = $row;
} // my requirement is based on tripId I want take the employee present count and emplyee absent count, in trip_member table I stored tripId (forienkey),empId,empPresentStatus.here come to know like empPresentStatus= '1' means he is absent, suppose empPresentStatus ='0' means is present.
$arrayName = array('status' => 'success', 'data' =>$data );
echo json_encode($arrayName);

Output I am getting

{
"status": "success",
"data": [
    {
        "tripId": "1",
        "cabNo": "CBX100",
        "absentCount": "1"
    },
    {
        "tripId": "2",
        "cabNo": "CBX101",
        "absentCount": "1"
    }
]
}

到现在好了。我想统计一下这次旅行中有多少员工。我不知道如何计算这个数字，如果有人知道意味着更新我的答案。

Expected Results

{
"status": "success",
"data": [
    {
        "tripId": "1",
        "cabNo": "CBX100",
        "absentCount": "1",
        "presentCount": "2"
    },
    {
        "tripId": "2",
        "cabNo": "CBX101",
        "absentCount": "1",
        "presentCount": "1"
    }
]
}

Updated table (cab_allocation)

allocationId     shiftTiming        routeId     cabId
  1                 1                  1        CBX100
  2                 1                  1        CBX101

Answer 1

这里可以使用子查询

Change your query with this one.

"SELECT a.tripId, a.cabNo, (select count(*) from trip_member as m WHERE m.tripId=a.tripId and m.empPresentStatus = '1') as presentcount,(select count(*) from trip_member as m WHERE m.tripId=a.tripId and m.empPresentStatus = '0') as absentcount FROM trip_details a WHERE a.tripStatus ='1' GROUP BY a.tripId"

如何使用 MySQL JOIN 从第二个 table 中获取两个计数结果

How to take two counts result from second table using MySQL JOIN

php

json

php-5.6