HI,Hick Gunter,
Thanks for you reply.
I find a strange problem.
For example, tableA contains two columns: implicit rowid, A_id.
we create index on A_id.
firstly, we used rowid to select the row, cost about 400 seconds;
secondly, we used A_id to select the row, cost about 200 seconds;
thirdly, we also used rowid to select the row, cost about 200 seconds.
if firstly,we used A_id to select the row, cost about 200 seconds;
secondly, we also used rowid to select the row, cost about 200 seconds.
the create index on A_id may have some influence to do with the rowid. and
from this example, I also think the rowid is not implicit index.
what do you think about this phenomenon?
best regards!
At 2015-12-11 15:15:16, "Hick Gunter" <hick at scigames.at> wrote:
>There is always an implicit index on the SQLite rowid and this is the fastest
>method to locate a row.
>
>The next best thing for retrieval speed is an index that matches the where
>clause. If you do not have one, SQLite may decide to create a temporary index
>anyway, but this depends on the query. Unless you have what is called a
>"covering index" (i.e. all fields mentioned in the query are present in the
>index), SQLite will retrieve a rowid from the index and use that to read the
>row from the table.
>
>Your second method uses a full table scan, i.e. SQLite is forced to retrieve
>every single row of the table to check i fit matches, which ist he slowest
>access method
>
>-----Urspr?ngliche Nachricht-----
>Von: sqlite-users-bounces at mailinglists.sqlite.org
>[mailto:sqlite-users-bounces at mailinglists.sqlite.org] Im Auftrag von ???
>Gesendet: Freitag, 11. Dezember 2015 07:40
>An: sqlite-users at mailinglists.sqlite.org
>Betreff: [sqlite] ABOUT ROWID
>
>Hi , Everyone,
> When I use methodone : select * from table_name where rowid = somenumber ?
> When I use methodtwo : select * from table_name where ordinaryid =
> somenumber ? (ordinary is not index)
> The table_name have at least two columns.
> I have some questions, as follows:
> 1.The methodone is faster than the methodtwo?
> 2.is rowid the default index?
>
> best wishes!
>
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>___________________________________________
> Gunter Hick
>Software Engineer
>Scientific Games International GmbH
>FN 157284 a, HG Wien
>Klitschgasse 2-4, A-1130 Vienna, Austria
>Tel: +43 1 80100 0
>E-Mail: hick at scigames.at
>
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