sorting by index

OwenTheSamoan

I am using php with mysql. To make things simple lets assume I have several columns in my database called username, password and login_date. I have added an index to the column login_date and called this index "A". Here is a select statement I would use---

select*from table where login_date="whatever";

How do I make my select statement so that is will sort by giving column login_date with index "A" priority over the other columns? How does it recognize there is an index that will make that field a priority or is it automatically a priority because there is an index associated to it?

subwayman

simply add an ORDER BY clause to your select and specify the columns you want the query sorted on and in what order. MYSQL will decide what indexes to use (IF ANY).

OwenTheSamoan

so all I really have to do is make a select statement like-

select*from table where login_date="whatever" order by login_date;

Just to clarify things, Mysql will automatically see that there is an index called "A" and sort using the index as a priority?

subwayman

weeelllll, yes . BUT

select*from table where login_date="whatever" order by login_date;

Ths will not achieve much unless "whatever" is a wildcard as if whatever is a date the query is already sorted as the results will only have one date.

select * from table where login_date="whatever" order by username;

Will return all the logins for the date ordered by username.

OwenTheSamoan

thank you very much