TSQL : conditional query - sql

Question

I have the following table :
| RoomID | OrderID | Occupancy | rn |
+--------+---------+-----------+----+
| 01 | 101 | Vacant | 1 |
| 01 | 102 | Occupied | 2 |
| 01 | 103 | Occupied | 3 |
| 01 | 104 | Vacant | 4 |
| 02 | 201 | Vacant | 1 |
| 02 | 202 | Occupied | 2 |
| 02 | 203 | Vacant | 3 |
| 03 | 301 | Vacant | 1 |
| 03 | 302 | Occupied | 2 |
| 03 | 303 | Occupied | 3 |
| 03 | 304 | Occupied | 4 |
| 04 | 401 | Occupied | 1 |
| 04 | 402 | Occupied | 2 |
| 04 | 403 | Vacant | 3 |
| 04 | 404 | Occupied | 4 |
I need to flag the RoomIDs where all of the following requirments are met as 'Yes' and if one or more requirements are not met as 'No':
when rn = 1 the Occupancy is vacant
When rn = 2 the Occupancy is Occupied
Any rn larger than 2 (3,4,5..) has an Occupancy of vacant
The result should look like the following:
| RoomID | OrderID |
+--------+---------+
| 01 | Yes |
| 02 | Yes |
| 03 | No |
| 04 | No |
I have an impression that this is easy but I cannot see it at the moment, thank you in advance for your help !

Answer 1

Builds on 'Yes' > 'No'
select RoomId,
min(case when rn<>2 and Occupancy='vacant'
or rn=2 and Occupancy='Occupied'
then 'Yes' else 'No' end) res
from myTable
group by RoomId

Answer 2

Using a CASE to calculate the rule for each row.
When the minimum of that rule (grouped by room_id) is 0, then at least 1 of them didn't follow the rule.
SELECT RoomID,
IIF(MIN(
CASE
WHEN rn <> 2 AND Occupancy = 'Vacant' THEN 1
WHEN rn = 2 AND Occupancy = 'Occupied' THEN 1
ELSE 0
END)=0,'No','Yes') as OccupancyRule
FROM RoomOccupancyTable
GROUP BY RoomID;

Answer 3

You can use Conditional Aggregation to check each condition.
with roomquery as (
select RoomId,
min(case when rn<>2 and Occupancy='vacant' then 1 else 0 end) cond1,
min(case when rn=2 and Occupancy='Occupied' then 1 else 0 end) cond2
from rooms r
group by RoomId)
select RoomId,
case when Cond1=1 and Cond2=1 then 'Yes' else 'No' end Status
from roomquery
Note: you can rewrite it and use only one condition or eve remove the CTE (with statement) altogether, but I believe this is more readable and maintainable.

Answer 4

I guess this will help you.
SELECT RoomID,
CASE WHEN ((rn = 1 OR rn > 2) AND Occupancy = 'Vacant') AND (rn = 2 AND Occupancy = 'Occupied') THEN 'Yes' ELSE 'No' END
FROM Table_Name

Answer 5

Here is another answer that counts the number of violations per RoomID in a subquery and then prints "yes" or "no" accordingly:
SELECT sub.roomid,
CASE WHEN sum(sub.orderid_no) IS NOT NULL THEN 'No'
ELSE 'Yes'
END AS orderID
FROM
(SELECT roomid,
CASE WHEN rn = 1 AND occupancy = 'occupied' THEN 1
WHEN rn = 2 AND occupancy = 'vacant' THEN 1
WHEN rn > 2 AND occupancy = 'occupied' THEN 1
END AS orderid_no
FROM T) sub
GROUP BY sub.roomid
Tested here: http://sqlfiddle.com/#!9/d9d467/14
Also, I think your output above is mistaken. According to your data, RoomID 01 should have OrderID "No"