Split String Value in SQL for Flexible Filtering - sql

Question

I have a function where in user can assign multiple categories (food, non food etc) to a certain Tenant. See sample Data Table
Table: tblSales
date tenant sales category
1/1/2015 tenant1 1000 Food,Non-Food,Kiosk
1/1/2015 tenant2 2000 Food
1/1/2015 tenant3 1000 Non-Food,Kiosk
The system should be able to load record when the user selected any of the categories listed in Category Column.
For example, User selected categories: Non-Food,Kiosk. Expected result should be:
date tenant sales category
1/1/2015 tenant1 1000 Food,Non-Food,Kiosk
1/1/2015 tenant3 1000 Non-Food,Kiosk
Since, Non-Food and Kiosk is seen in Tenants 1 and 3.
So, what I think, the process should be a string manipulation first on the value of Category column, splitting each word delimited by comma. I have code which does not work correctly
#Category nvarchar(500) = 'Non-Food,Kiosk' --User selected
SELECT date,tenant,sales,category
FROM tblSales
WHERE (category in (SELECT val FROM dbo.split (#Category, #delimeter)))
That does not seem to work because the one it is splitting is the User Selected Categories and not the value of the data itself. I tried this
#Category nvarchar(500) = 'Non-Food,Kiosk' --User selected
SELECT date,tenant,sales,category
FROM tblSales
WHERE ((SELECT val FROM dbo.split (category, #delimeter)) in (SELECT val FROM dbo.split (#Category, #delimeter)))
But it resulted to this error
Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

Answer 1

In addition to Tim's answer (he is absolutely right about CSV fields in databases!) please note that SQL Server 2016 introduced STRING_SPLIT function. For a single category it's as simple as:
SELECT
date
,tenant
,sales
,category
FROM tblSales
WHERE #Category IN (SELECT value FROM STRING_SPLIT(category, ','))
For a comma delimited list of categories you have to use it twice together with EXISTS:
WHERE EXISTS
(
SELECT *
FROM STRING_SPLIT(category, ',')
WHERE value IN (SELECT value FROM STRING_SPLIT(#Category, ','))
)
If you're using an older SQL Server version you may write your own STRING_SPLIT function, take a look to T-SQL split string. You can use that function with the same syntax as above (please note I wrote code here and it's untested so you may need some fixes).
Note about performance: from QP you can check how sub-queries will be executed, from a naive point of view I'd say CTE, temp-tables and sub-queries have roughly same performance (in this simple case) but if this code is performance critical you'd better perform some benchmark (with real data and a real-world access scenario).

Answer 2

In general, it is bad practice to store CSV data into a database column, because, as you are currently seeing, it renders many of the advantages a database has not usable.
However, I think you might be able to get away with just using LIKE. Assuming the user selected the categories Non-Food and Kiosk, you could try the following query:
SELECT date,
tenant,
sales,
category
FROM tblSales
WHERE category LIKE 'Non-Food' OR
category LIKE 'Kiosk'

Answer 3

Try with the below code .
Create a function to split delemited strings.
CREATE FUNCTION SplitWords
(
#Input NVARCHAR(MAX),
#Character CHAR(1)
)
RETURNS #Output TABLE (
Item NVARCHAR(1000)
)
AS
BEGIN
DECLARE #StartIndex INT, #EndIndex INT
SET #StartIndex = 1
IF SUBSTRING(#Input, LEN(#Input) - 1, LEN(#Input)) <> #Character
BEGIN
SET #Input = #Input + #Character
END
WHILE CHARINDEX(#Character, #Input) > 0
BEGIN
SET #EndIndex = CHARINDEX(#Character, #Input)
INSERT INTO #Output(Item)
SELECT SUBSTRING(#Input, #StartIndex, #EndIndex - 1)
SET #Input = SUBSTRING(#Input, #EndIndex + 1, LEN(#Input))
END
RETURN
END
GO
create a input tabl inside your prcedure /script and keep the split data in that. here your input is #Category
DECLARE #input TABLE (item VARCHAR(50))
INSERT INTO #input
SELECT Item
FROM [dbo].SplitWords (#Category, ',')
make a join using like operator with your actual table
SELECT DISTINCT a.date,
a.tenant,
a.sales,
a.category
FROM tblSales s
JOIN #input a
ON category LIKE '%'+item+'%'

Answer 4

You can try following SQL Select statement where I used my user defined SQL function for split string task
declare #Category nvarchar(500) = 'Non-Food,Kiosk'
declare #cnt int = (select COUNT(*) from dbo.SPLIT(#Category,','))
;with cte as (
select
t.*, COUNT(*) over (partition by tenant) cnt
from dbo.SPLIT(#Category,',') u
inner join (
select
tblSales.*, c.val
from tblSales
cross apply dbo.SPLIT(tblSales.category,',') c
) t on u.val = t.val
)
select distinct tenant from cte where cnt = #cnt