Best way to compare the end of a string, use RIGHT, LIKE or other?

sql sql-server tsql optimization string-comparison
Djof picture Djof · Sep 12, 2011 · Viewed 33k times · Source

I need to compare the end of strings against a list of possible ending in a stored procedure. It will be called a lot and there are around 10-15 candidate endings. At this point a code-only solution is preferable to creating tables dedicated to this. Something that would be like:

IF (ENDSWITH(@var, 'foo') OR
    ENDSWITH(@var, 'bar') OR
    ENDSWITH(@var, 'badger') OR
    ENDSWITH(@var, 'snake'))
(
)

I'm looking for the best way in terms of speed, but also maintainability. Candidates that I know of are

  • RIGHT, my favorite so far but it means I have to hardcode the string length, so can be prone to error. It also means cutting the source string many times.

    IF ((LEN(@var) >= 3 AND RIGHT(@var, 3) = 'foo')) OR ...

  • LIKE, probably slower, but a bit cleaner

    IF (@var LIKE '%foo') OR ...

  • CHARINDEX, most probably slower since it searches the whole string

  • SUBSTRING, most probably equivalent to RIGHT and much more ugly

  • SQLCLR to create my own ENDSWITH, it can be pretty quick

There might be better ways I don't know of. What do you think?

Answer

Joe Stefanelli picture Joe Stefanelli · Sep 12, 2011

The best way to optimize this for SQL might be to store the REVERSE string value in another column that is indexed and search the left side of that using either LEFT or LIKE.

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