Find the missing group entry in sql server - sql

Question

I have the below table:
Declare #t table (Name nvarchar(80))
Insert into #t values
('ABC:CE')
,('ABC:LI')
,('ABC:XP')
,('ABD:CE')
,('ABD:LI')
,('ABE:LI')
,('ABE:XP')
,('ABF:XP')
I have 3 categories CE,LI,XP. I wanted to check which group is missing in the name.
I tried below Query:
select SUBSTRING(Name,1,charindex(':',Name)-1),count(1) as grplist from #t
group by SUBSTRING(Name,1,charindex(':',Name)-1)
having count(1) <3
Expected output:
Name
ABD:XP
ABE:CE
ABF:LI
ABF:CE
Can you guys help me where I am going wrong this:

Answer 1

Try this:
Declare #t table (Name nvarchar(80))
Insert into #t values
('ABC:CE')
,('ABC:LI')
,('ABC:XP')
,('ABD:CE')
,('ABD:LI')
,('ABE:LI')
,('ABE:XP')
,('ABF:XP');
WITH DataSource ([group], [category]) AS
(
SELECT SUBSTRING([Name], 1, CHARINDEX(':', [Name]) - 1)
,SUBSTRING([Name], CHARINDEX(':', [Name]) + 1, 100)
FROM #t
)
SELECT DISTINCT G.[group], C.[category]
FROM DataSource G
CROSS APPLY
(
SELECT DISTINCT [category]
FROM DataSource
) C
WHERE NOT EXISTS
(
SELECT 1
FROM DataSource DS
WHERE DS.[group] = G.[group]
AND DS.[category] = C.[category]
)

Answer 2

You want to select the values that are not in the table. For this to happen, you must first create these values. You do this with a cross join:
select n.name + ':' + c.category as missing
from (select distinct substring(name, 1, charindex(':', name) - 1) as name from #t) n
cross join (values ('CE'), ('LI'), ('XP')) c(category)
except
select name from #t
order by missing;
Demo: http://www.sqlfiddle.com/#!18/c99228/4

Answer 3

I see there's an answer here already but here's my take, looks similar mine may be less efficient but hey more the merrier :)
Declare #t table (Name nvarchar(80))
Insert into #t values
('ABC:CE')
,('ABC:LI')
,('ABC:XP')
,('ABD:CE')
,('ABD:LI')
,('ABE:LI')
,('ABE:XP')
,('ABF:XP')
Declare #c table (Cat nvarchar(2))
Insert into #c values
('CE')
,('LI')
,('XP')
SELECT
possible.prefix
,possible.Cat
,possible.prefix + ':' + possible.Cat
--,selector.Prefix
--,selector.suffix
FROM
(
select
SUBSTRING(Name,1,charindex(':',Name)-1) as prefix
,SUBSTRING(Name,charindex(':',Name)+1,2) as suffix
from #t
) as selector
right Join
(
SELECT DISTINCT
SUBSTRING(Name,1,charindex(':',Name)-1) as prefix
-- ,SUBSTRING(Name,charindex(':',Name)+1,2) as suffix
,Cat
FROM #t
cross join #c
) possible
ON selector.prefix = possible.prefix
and selector.suffix = possible.Cat
where selector.suffix is null