2 diff ways to query, which is better?

this is for mysql and php.

let say i have to grab info from 2 different tables

is it better/faster to do it like this:

select a.name, a.phone, a.address, b.bookid, b.bookdescription
from user a, book b
where a.ID = b.ID
and a.ID = 300

or is it better/faster to do 2 diff queries?

select a.name, a.phone, a.address
from user a
where a.ID = 300

select b.bookid, b.bookdescription
from book b
where b.ID = 300?

Figure it out for yourself. Use the DESCRIBE sql command to have the sql server tell you which it thinks will be faster.

In this case, I suspect you will find the join to be faster.

i didn't know you can use the describe to do that

thanks

In virtually all cases the join would be better. I think the one exception is if you somehow end up performing a cartesian product.

the reason why i am wondering is because if you imagin how a join works...

let say 2 tables, each have 100 records

a join will end up filtering a 10000 tables

where as if i do it twice

then it'll be filtering 2 100 tables

10000 records just seem a lot to me that's all

That is if you do not provide a JOIN condition, which results in a cartesian product as I said.

i see what are you saying

duh!
thanks a lot! you've been helpful!🙂

It's actually more effective to use one well-designed query if you can in 90% of situations. Try using an inner join if you can...?