时钟的相关查询逻辑

Question

I could really use some help figuring out a query for the following scenario.

tblStaff

| ESID | EID | FName | LName  |
+------+-----+-------+--------+
| 1    | 10  | Joe   | Smith  |
| 2    | 10  | Dan   | Jones  |
| 3    | 10  | Rick  | Brown  |
| 4    | 10  | Pete  | Miller |
| 5    | 10  | Ken   | White  |

tblStaffTime

| TCID | EID | ESID | DTIn                    | DTOut                   |
+------+-----+------+-------------------------+-------------------------+
| 1    | 10  | 1    | 2013-09-22 08:00:00.000 | 2013-09-22 17:00:00.000 |
| 2    | 10  | 1    | 2013-09-23 08:00:00.000 | NULL                    |
| 3    | 10  | 2    | 2013-09-23 08:00:00.000 | 2013-09-23 17:00:00.000 |
| 4    | 10  | 3    | 2013-09-22 08:00:00.000 | 2013-09-22 17:00:00.000 |
| 5    | 10  | 3    | 2013-09-23 08:00:00.000 | NULL                    |

My Objectives are: List all people with EID equal to 10 where the most recent DTOut is not null or they have no record in tblStaffTime at all for this EID. In other words, a list of who is ready to be clocked in for all staff with an EID equal to 10.

My SQL so far:

SELECT tblStaff.ESID AS ID,tblStaff.SFirst + CHAR(32) + tblStaff.SLast AS StaffName
FROM tblStaff
LEFT JOIN tblStaffTime ON tblStaff.ESID = tblStaffTime.ESID
WHERE tblStaff.ESID = (SELECT ESID FROM tblStaffTime WHERE EID = '10' AND ESID = tblStaffTime.ESID AND DTIn IS NOT NULL AND DTOut IS NOT NULL)
UNION ALL
SELECT tblStaff.ESID AS ID,tblStaff.SFirst + CHAR(32) + tblStaff.SLast AS StaffName
FROM tblStaff
LEFT JOIN tblStaffTime ON tblStaff.ESID = tblStaffTime.ESID
WHERE NOT EXISTS (SELECT 1 FROM tblStaffTime WHERE tblStaffTime.ESID = tblStaff.ESID) AND tblStaff.EID = '10'
ORDER BY tblStaff.SFirst + CHAR(32) + tblStaff.SLast

Desired Output:

| ESID | StaffName   |
+------+-------------+
| 2    | Dan Jones   |
| 5    | Ken White   |
| 4    | Pete Miller |

South of my Union solves my issue of getting staff who have not clocked in for this EID. My major problem is the northern part of my union. I need to get the most recent DTIn and see if DTOut is null or not for that record to determine if they should be listed as ready to clock in. I'm certain this SQL can all be written much cleaner. I'll leave it to the experts now.

Answer 1

If you're using SQL Server 2005 or later, you can use window functions to help with this

The left outer join helps include people with no record, and the order by DTIn lets us pick the latest time record when there is one

With x as (
    Select
        s.ESID,
        s.EID,
        s.FName,
        s.LName,
        t.DTIn,
        t.DTOut,
        row_number() over (partition by s.ESID, s.EID order by DTIn Desc) rn
    From
        tblStaff s
            Left Outer Join
        tblStaffTime t
            On s.ESID = t.ESID and s.EID = t.EID
)
Select
    x.ESID,
    x.EID,
    x.FName,
    x.LName
From
    x
Where
    x.EID = 10 And
    x.rn = 1 And (
      x.DTIn Is Null Or -- no time records
      x.DTOut IS Not Null -- latest time record has not null clock out
    )

Example Fiddle