根据另一个表中的一个列表查找值。Pivot

Question

Help needed.

I have three tables

1. Building_master - columns: BuildingCode, Building Name

2. Floor_master - columns: FloorCode, Floor Name, BuildingCode

3. Room_Master - columns: RoomCode, RoomName, RoomFloor, RoomBulding

I want to fill the GridView when I select Building Name from Building_master table where the output will be something like below

Building Name: A

Floor               
1   Room 101    Room 102    Room 103    Room 104
2   Room 201    Room 202    Room 203
3   Room 301    Room 302    Room 303    Room 304

Kindly help to create a SQL query for the desired output

Answer 1

To pivot over a fixed number of columns (that is, the maximum number of rooms per floor), you can join, then use window functions and conditional aggregation:

select  
    building_name,
    floor_name,
    max(case when rn = 1 then room_name end) room1,
    max(case when rn = 2 then room_name end) room2,
    max(case when rn = 3 then room_name end) room3
from (
    select
        b.building_code,
        b.building_name,
        f.floor_code,
        f.floor_name,
        r.room_name,
        row_number() over(
            partition by b.building_code, f.floor_code order by r.room_code
        ) rn
    from building_master b
    inner join floor_master f
        on f.building_code = b.building_code
    inner join room_master r 
        on  r.room_floor = f.floor_code 
        and r.room_building = b.building_code
) t
group by b.building_code, b.building_name, f.floor_code, f.floor_name

I had to make a few guesses about the relationships in your schema, that you might need to review.

You can handle more rooms by floor by adding more max() expressions to the outer select .