How do I take the values of one record in a table and split it into multiple columns? - sql

Question

I have two tables which contain the following fields I need to use:
Master Data: Master_ID (PK)
Item Data: Crate_ID, Master_ID (FK), Item_Type_ID, Item_Type_Description, Item_Date
The Item_Type_ID has several different numerical values, i.e. 10, 20, 30, 40, 50 ... 100 ... etc.
Each numerical value represents a type, i.e. Veggie, Fruit, Grains, Meat, etc.
The Item_Type_Description are things like: Fruit, Veggies, Grains, Meat, etc.
The Item_Date is a single date that identifies when that particular item (based upon Item_ID) was added to the Crate.
Note that there can only ever be one unique Item_Type_ID per Master_ID. Meaning, Item_Type_ID '10' can only ever be related to Master_ID '1234' once. An Item_Type_ID can be related to many different Master_IDs, but each of those Master_IDs, it can only be related once.
The issue I am having is that I can get the combined results, but for each Item_Type_ID, a distinct record/row is being created.
Here is the code I have generated thus far, which is giving me the incorrect Results:
USE Shipping
GO
BEGIN
SELECT
vmi.master_id
,CASE
WHEN vid.item_type_id = 10 THEN vid_item_date
ELSE NULL
END as 'Fruit_Item_Date'
,CASE
WHEN vid.item_type_id = 20 THEN vid_item_date
ELSE NULL
END as 'Veggie_Item_Date'
,CASE
WHEN vid.item_type_id = 30 THEN vid_item_date
ELSE NULL
END as 'Grains_Item_Date'
,CASE
WHEN vid.item_type_id = 40 THEN vid_item_date
ELSE NULL
END as 'Meat_Item_Date'
FROM v_master_data vmi
LEFT JOIN v_item_data vid ON vmi.master_id = vid.master_id
WHERE vid.item_type_id IN (10,20,30,40)
END
GO
Any input, pointers, assistance, direction, advice, is greatly appreciated.
Running SQL Server 2016, accessed via SQL Server Management Studio v18.

Answer 1

Perhaps this will give you a little nudge
PIVOT
Select Master_ID
,Fruit_Date = [10]
,Veggie_Date = [20]
,Grains_Date = [30]
,Meat_Date = [40]
From (
Select Master_ID
,Item_Type_ID
,Item_Date
From YourTable
) src
Pivot ( max(Item_Date) for Item_Type_ID in ( [10],[20],[30],[40] ) ) pvt
Conditional Aggregation
Select Master_ID
,Fruit_Date = max( case when Iten_Type_ID =10 then Item_Date end)
,Veggie_Date = max( case when Iten_Type_ID =20 then Item_Date end)
,Grains_Date = max( case when Iten_Type_ID =30 then Item_Date end)
,Meat_Date = max( case when Iten_Type_ID =40 then Item_Date end)
From YourTable
Group By Master_ID
A conditional aggregation offers a bit more flexibility and is often more performant.