Re: [SQL] Table indexes in a SELECT with JOIN´s
От | Pavel Stehule |
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Тема | Re: [SQL] Table indexes in a SELECT with JOIN´s |
Дата | |
Msg-id | CAFj8pRAgLc_AM6WE3_EgzhKziUx+SieYN5b8CCWGu4Nd8pnfwQ@mail.gmail.com обсуждение исходный текст |
Ответ на | Table indexes in a SELECT with JOIN´s (JORGE MALDONADO <jorgemal1960@gmail.com>) |
Список | pgsql-sql |
Hello
2013/4/20 JORGE MALDONADO <jorgemal1960@gmail.com>
Let´s suppose that I have a SELECT statement that joins more than one table and such a statement is order by fields that belong not only to the table in the FROM but also by fields in the tables that are part of the JOIN´s. How does indexes should be considered in a case like this? For example:SELECT artist_name, author_name, producer_name, song_nameFROM tbl_songsINNER JOIN tbl_artists ON tbl_artists.artistid = tbl_songs_artistidINNER JOIN tbl_authors ON tbl_authors.authorid = tbl_songs_authoridINNER JOIN tbl_producers ON tbl_producers.producerid = tbl_songs_produceridORDER BY song_name
It depends on size of relations - you don't need indexes on small tables - hash join will be used. For bigger tables indexes on PK (automatically) and FK are good idea.
Regards
Pavel
Pavel
Respectfully,Jorge Maldonado
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