Searching a column containing CSV data in a MySQL table for existence of input values

Question

I have a table say, ITEM, in MySQL that stores data as follows:

ID    FEATURES
--------------------
1     AB,CD,EF,XY
2     PQ,AC,A3,B3
3     AB,CDE
4     AB         


        

Answer 1

First of all, the database should of course not contain comma separated values, but you are hopefully aware of this already. If the table was normalised, you could easily get the items using a query like:

select distinct i.Itemid
from Item i
inner join ItemFeature f on f.ItemId = i.ItemId
where f.Feature in ('AB', 'PQ')

You can match the strings in the comma separated values, but it's not very efficient:

select Id
from Item
where
  instr(concat(',', Features, ','), ',AB,') <> 0 or
  instr(concat(',', Features, ','), ',PQ,') <> 0