mysql - query taking long to execute -


i using sql, want delete repeating rows table emaillikebusiness_2 compares data table called per2 query using is

delete        emaillikebusiness_2       emaillikebusiness_2.email_id   in (     select      per2.businessemail2             per2 );

the explain statement gives output

'1', 'primary', 'emaillikebusiness_2', 'all', null, null, null, null, '30670', 'using where' '2', 'dependent subquery', 'per2', 'all', 'idx_email2person2', null, null, null, '24710', 'range checked each record (index map: 0x1)'

i have created index on both table , tried creating index on individual table still query taking long time execute. there anyway can reduce query execution time

mysql tends optimize where ... in (select ...) poorly. use join instead:

delete e.* emaillikebusiness_2 e join per2 p on e.email_id = p.businessemail2

i've found in, full scan of first table, searching email_id in index of second table, if first table larger second one. join, more efficient match between indexes of 2 tables.


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