Index with a column varchar(50)

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Index with a column varchar(50)

sistemas_casinomnes

SSChasing Mays

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February 6, 2014 at 6:34 am

#151318

Is recommended that créate an index with a column that is varchar?

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Eugene Elutin SSC Guru Points: 59322 More actions · Answer 1

It depends...

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Lowell SSC Guru Points: 323504 More actions · Answer 2

the usual answer is it depends on how you are searching;

if you are searching on last name (WHERE LName = 'McArther')

then yes, an index would help a query like that.

anything that starts with would also benefit form the index: ie

LIKE 'MC%'

but if you are looking for substrings, then the index would not be used, a table scan would occur instead:

LIKE '%the%'

Lowell

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Eugene Elutin SSC Guru Points: 59322 More actions · Answer 3

Lowell (2/6/2014)
the usual answer is it depends on how you are searching;
if you are searching on last name (WHERE LName = 'McArther')
then yes, an index would help a query like that.
...

It also depends on data density and distribution. Let say you have 1,000,001 rows in your table and 1,000,000 of them have LName = 'McArther' for one or another reason. Index will not help you much in this case...

_____________________________________________
"The only true wisdom is in knowing you know nothing"
"O skol'ko nam otkrytiy chudnyh prevnosit microsofta duh!":-D
(So many miracle inventions provided by MS to us...)

How to post your question to get the best and quick help[/url]