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Re: using like vs = in exact match

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migurus (migurus@yahoo.com) writes:
> I came across a situation where application builds a list of names by
> matching first three letters entered by user. The list of names does not
> have any duplicates  The query generated by app is 
>   SELECT LAST_NAME
>   FROM NAME_LIST
>   WHERE LAST_NAME LIKE 'GRE%'
> 
> The result set is coming back as
>   GREAGORS
>   GREEN
>   GREISS
> 
> Now user selects one line and application should retrieve that line, The
> app generate the same query as in the 3 letter case above 
>   SELECT LAST_NAME
>   FROM NAME_LIST
>   WHERE LAST_NAME LIKE 'GREEN%'
> 
> I don't like the lazy programming, it should have been WHERE LAST_NAME =
> 'GREEN' in my view,  my guts feeling is that the access plan for LIKE
> clause might be inefficient comparing to the = clause. 
> The example above is simplified. But in essence is LIKE less likely to
> produce a perfect plan comparing to =, or there is no justification to
> my rant. 

I would execpt there is no difference of practical importance, although 
may some measurable difference if you 200 processes all sending this LIKE
query.

But apart from that, I agree with you. If nothing else, assume that there 
also is a GREENE in the list.



-- 
Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se

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using like vs = in exact match migurus <migurus@yahoo.com> - 2012-12-26 10:22 -0800
  Re: using like vs = in exact match Erland Sommarskog <esquel@sommarskog.se> - 2012-12-26 20:10 +0100

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