CODEWITHSUNDEEP
mysqlsqlregex
Pavlos
Pavlos

Reputation: 270

Count occurrences of character in a string using MySQL

Example Words: a, akkka, akokaa, kokoko, kakao, oooaooa, kkako, kakaoa

I need the regexp witch gives words with 2 or less 'a' but not the words without 'a'

Result: a, akka, kakao, oooaooa, kkako

Ok actually I am using:

SELECT word FROM dictionary_gr WHERE word REGEXP 'λ{2,3}' LIMIT 0 , 30

this returns 0 lines there are words with 2 λ's and 3 λ's

Upvotes: 26

Views: 30106

Answers (3)

Art
Art

Reputation: 5782

Quick and dirty:

Select word, number_of_as From
(
 Select 'akkka' word, REGEXP_COUNT('akkka', 'a') number_of_as From dual
)
Where number_of_as <= 2
/

Upvotes: -3

Woot4Moo
Woot4Moo

Reputation: 24316

select *  
from table  
where  LENGTH(name) - LENGTH(REPLACE(name, 'a', '')) between 1 and 2

Updated to use between.

Upvotes: 43

Xophmeister
Xophmeister

Reputation: 9211

I don't know what MySQL supports in terms of lookaround assertions, but the following will do the trick:

^(?=.*a.*a?.*)(?!.*a.*a.*a.*).*$

We have a lookahead assertion that matches 1 or 2 a characters in the string. Then we have a negative lookahead that disregards 3 or more as anywhere in the string. Then the final pattern just matches the whole string, providing the first two assertions are satisfied.

If MySQL doesn't support lookarounds, then @Woot4Moo's answer would be the way to go.

Upvotes: 2

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