Is there such a thing as a 'IS IN' query - sql

Question

I have 3 tables:
Silk_Skey Name
1 Black White Checks Yellow Arms
2 Black Crimson Stripes
3 Crimson Yellow Stripes
Sub Colour Major Colour
Black Black
White White
Yellow Yellow
Crimson Red
MajorColour_Skey Major Colour
1 Black
2 White
3 Yellow
4 Red
And I want to achieve this:
ID Silk_Skey MajorColour_Skey
1 1 1
2 1 2
3 1 3
4 2 1
5 2 4
6 3 3
7 3 4
What I need to do is create a linked table matching all the colours from the 3 tables and break down the silks names so I would show 4 lines in the new table) see SQL below. My boss has advised me to use a 'IS IN' query but I have no idea what that is can you help?
SELECT s.Silks_Skey, mc.MajorColour_Skey
FROM Silks s INNER JOIN SubColour sc on sc.SubColour **'IS IN HERE'** s.SilksName
INNER JOIN MajorColour mc
ON sc.MajorColour = mc.MajorColour

Answer 1

You can use IN
AND table.column IN ('a','b','c')
or
AND table.column IN (1,2,3)
or if you're looking for a string like something you can do
AND table.column LIKE '%word' -- table.column ends with 'word'
AND table.column LIKE 'word%' -- table.column starts with 'word'
AND table.column LIKE '%word%' -- table.column has 'word' anywhere in the column

Answer 2

This is a design doomed to poor performance and awkward and painful to write queries. If your database will never be large, then it may be workable, but if it will be large, you cannot use this design structure and hope to have good performance because you will not be able to properly use indexes. Personally I would add a silk colors table related to the silks table and store the colors indivudally. One of the first rules of database design is never store more than one piece of informatino in a field. You are storing a list which always means you need a related table to have effective use of the database.
One clue to a bad (and over time usually unworkable)database design is if you need to join using functions or caluations of any type or if you need to use wildcards at the start of a phrase in a like clause. Fix this now and things will be much smoother, maintenance will take less time and performacne will be better. There is no upside to your current structure at all.
You may need to take a bit of extra time to parse and store the silk names by individual color, but the time you save in querying the database will be significant becasue you can now make use of a join and then use indexes. Search for fn_split and you will see a method of spliting the silk names into individual colors that you can use when you insert the records.
If you foolishly decide to retain the current structure, then look into using fuilltext search. It wil be faster than using a like clause with a wildcard as the first character.

Answer 3

For what you want to do, you need to do string manipulation because you are trying to compare one color to a list of colors in a string.
The like operator can do this. Try this on clause:
on ' '+ s.SilksName +' ' like '% '+sc.SubColour+' %'
This checks to see if a given color (sc.SubColour) in in the list (s.SilksName). For instance, if you have a list like 'RED GREEN' this will match either '%RED%' or '%GREEN%'.
The purpose of concatenating white space is to avoid partial-word matches. For instance, "blue-green" would match both "blue" and "green" without the delimiters.
The following query returns 7 rows, which seems to be correct (3 for the first row in silks and 2 for each of the other two):
with silks as (
select 1 as silks_skey, 'Black White Checks Yellow Arms' as silksname union all
select 2, 'Black Crimson Stripes' union all
select 3, 'Crimson Yellow Stripes'
),
subcolour as (
select 'black' as subcolour, 'black' as majorcolour union all
select 'white', 'white' union all
select 'yellow', 'yellow' union all
select 'crimson', 'red'
),
MajorColour as (
select 1 as MajorColour_skey, 'black' as MajorColour union all
select 2, 'white' union all
select 3, 'yellow' union all
select 4, 'red'
)
SELECT s.Silks_Skey, mc.MajorColour_Skey
FROM Silks s INNER JOIN SubColour sc on ' ' + s.SilksName + ' ' like '% ' + sc.SubColour + ' %'
INNER JOIN MajorColour mc
ON sc.MajorColour = mc.MajorColour

Answer 4

Sounds like what you really want to do is split the Name field on spaces and then for each one of those values which is contained in the colours table (joined on the sub-colour given that major colours are valid sub-colours too) you want one entry in a new table. Problem is that there is no intrinsic T-SQL function for splitting strings. To do that your best bet is to visit Erland Sommarskog's definitive answer on how to do this.
An alternative, and one which is not very neat and may or may not work, is to use the CONTAINS keyword in your predicate. However in order to achieve this you need to use full text indexing
and I suspect using Erland's excellent giudes on splitting strings and arrays in SQL will be more appropriate and faster.

Answer 5

This is the answer folks, thanks for all your ideas.
Select S.[Silks_Skey], MC.[MajorColour_Skey]
from [dbo].[Silks] S
inner join [dbo].[SubColour] SC on CHARINDEX(SC.[SubColour],S.[SilksName]) <> 0
inner join [dbo].[MajorColour] MC on SC.[MajorColour] = MC.[MajorColour]
UNION ALL
Select S.[Silks_Skey], MC.[MajorColour_Skey]
from [dbo].[Silks] S
inner join [dbo].[MajorColour] MC on CHARINDEX(MC.[MajorColour],S.[SilksName]) <> 0
ORDER BY S.[Silks_Skey]