Finding Last Rows value

skc

Hi All,
How to find the last rows value for defining new insert id ?

regards
skc

cahva

I'm assuming you use mysql. Do you mean:

SELECT MAX(id) AS last_id FROM table

That will fetch you the last id.
If you want to know the just inserted id, you can use:

$lastid = mysql_insert_id();

..just after the insert.

bradgrafelman

skc wrote:
How to find the last rows value for defining new insert id ?

You don't. You set the id column to auto_increment and let the DB assign the next id (i.e. don't even list the id column in your INSERT queries).

laserlight

Incidentally

SELECT MAX(id) AS last_id FROM table

may fetch you the maximum id value, but it may not necessarily be the last id (though it probably will be). The reason is that depending on the database engine and how the auto increment is configured, there may be a wraparound to unused ids from rows that were deleted.

That said, follow bradgrafelman's advice if what you really want to do is to use auto increment for a new row.

bradgrafelman

laserlight wrote:
it may not necessarily be the last id

And to continue...

Even if it does give you the last id, the only thing you know is the last id at that time. You don't know if it's the last id when you go to do your INSERT statement. This is commonly referred to as a race condition; one query grabs the next id value, forms a new query with that id... meanwhile, other processes could be doing the same thing, though only one is going to win.