…. You should pick something else if you have a good reason to do it – if you would benefit from …to add the index on column using order by clause. A: If index is used for ORDER BY the …search condition WHERE A=5 ORDER BY B will use index (A,B) for sorting optimization, for more complicated conditions …
Post: Multi Column indexes vs Index Merge
September 19, 2009 By 31 Comments
…(for MyISAM tables) or something else. It is important internally …If where clause from first column selects 5% of the rows and applying where clause…conditions it would do the index merge: mysql [localhost] {msandbox} (test) > explain select avg(length(val)) from idxtest ignore index (combined) where…
Post: ORDER BY ... LIMIT Performance Optimization
September 1, 2006 By 100 Comments
…general this type of ORDER BY looks like: SELECT ….. WHERE [conditions] ORDER BY [sort] LIMIT N,M Make sure…The main thing to watch for, if you do not have full where clause resolved by index is how many … connections and it is enough. If you do not do anything else make sure you block requests with…
Post: MySQL Backup tools used by Percona Remote DBA for MySQL
March 13, 2013 By 8 Comments
… UPDATE or DELETE and forgets the where clause or filters weren’t quite right…’s hope your backups are somewhere else! You lose a PSU or … it’s strong points given the conditions. Percona XtraBackup for MySQL for binary backups…separate script use_https = True, especially if your data is not encrypted …
