How do I compare these 2 tables ?

[habbardone]

Hi,

I have two comparisons that I need to do and they are a bit
beyond my knowledge, would appreciate some help.

I have two tables that have an identical structure,
one is the incoming daily update, tableA which I want to
compare to the history tableB.

Both structures look like this:
id, title, desc, data1, data2, ... data18

B[/B]
The first comparison is to check for new rows. I think I can
do this by using the LEFT JOIN command

Is this how I do it ?

$query = "SELECT tableA.*, tableB.* FROM tableA LEFT JOIN tableB ON tableA.id = tableB.id"; 

$result = mysql_query($query) or die(mysql_error());

B[/B]
My second comparison is to compare all the rows that have same ids
but have differences in the other fields i.e. not NEW records but CHANGED records.

[Kudose]

The easiest method would be have a column that you know will be updated, like a timestamp, then select rows from tableB where the timestamp is greater than tableA for example.

For your second question, see MySQL's syntax for REPLACE INTO. Be sure the column id is your primary key.

[habbardone]

Thanks for your reply.

I read all about and got a bit turned off from
using it as many seem to have re-numbering/re-indexing problems.

I thought my LEFT JOIN would be more efficient that stepping though all the
rows ? However I think I am going to have to step through all the rows to do this comparision with individual records.