Using LIKE in an Oracle IN clause

Question

I know I can write a query that will return all rows that contain any number of values in a given column, like so:

Select * from tbl where my_col in (val1, v         


        

Answer 1

select * from tbl 
where my_col like '%val1%' or my_col like'%val2%' or my_col like '%val3%', ...

But beware, that might be quite slow... Alternatively, you could insert all acceptable values (including % signs) into a table and semi-join that table:

select * from tbl
where exists (select 1 from all_likes where tbl.my_col like all_likes.value)

For true full-text search, you might want to look at Oracle Text:

http://www.oracle.com/technetwork/database/enterprise-edition/index-098492.html

Answer 2

A REGEXP_LIKE will do a case-insensitive regexp search.

select * from Users where Regexp_Like (User_Name, 'karl|anders|leif','i')

This will be executed as a full table scan - just as the LIKE or solution, so the performance will be really bad if the table is not small. If it's not used often at all, it might be ok.

If you need some kind of performance, you will need Oracle Text (or some external indexer).

To get substring indexing with Oracle Text you will need a CONTEXT index. It's a bit involved as it's made for indexing large documents and text using a lot of smarts. If you have particular needs, such as substring searches in numbers and all words (including "the" "an" "a", spaces, etc) , you need to create custom lexers to remove some of the smart stuff...

If you insert a lot of data, Oracle Text will not make things faster, especially if you need the index to be updated within the transactions and not periodically.

Answer 3

No, you cannot do this. The values in the IN clause must be exact matches. You could modify the select thusly:

SELECT *
  FROM tbl
 WHERE my_col LIKE %val1%
    OR my_col LIKE %val2%
    OR my_col LIKE %val3%
 ...

If the val1, val2, val3... are similar enough, you might be able to use regular expressions in the REGEXP_LIKE operator.