Determining LEFT or RIGHT join table?

**solidcodes** · May 5, 2008 18:58

I know this is very basic question.

But i just want to remove my confusion.

How do i know if the table is in the LEFT side or RIGHT side?

Thank you.

**ctx2002** · May 5, 2008 22:33

if your put table at left side then it in the left side.

**solidcodes** · May 5, 2008 23:06

if your put table at left side then it in the left side.

ha ha very funny answer.

anyone can answer this question properly please.

**r937** · May 6, 2008 04:19

Originally Posted by solidcodes

How do i know if the table is in the LEFT side or RIGHT side?

by figuring out which table you want to have all rows from

if you say A inner join B, then you get only rows from each table that match

if you say A left outer join B, then you get all rows from A, plus matching rows from B, if any

if you say A right outer join B, then you get all rows from B, plus matching rows from A, if any

so it depends on what you want

**barbara1712** · May 6, 2008 04:36

Dont know much about the joins
Why should we use joins?

what is the difference between
if you say A left join B, then you get all rows from A, plus matching rows from B, if any

and

if you say A left outer join B, then you get all rows from A, plus matching rows from B, if any

**r937** · May 6, 2008 04:44

the difference is only the optional keyword OUTER

why should you use joins? because they're faster than retrieving data from one table, then using the key values to get rows from the second table by performing a query in a loop

a bazillion times faster

**barbara1712** · May 6, 2008 05:14

thanks a lot r937.
One more about locking.
I have read about locking,but I still did not get the exact mechanism like
what is the meaning of read or write . What about row lenel locking?

Can you give me a link so that I can know the locking mechanism?