如何有效地检查记录是否存在于mysql表中？

Question

I'm coding PHP kohana application and in one part of it I need to insert a few records into table.

My table structure:

TABLE BOOKINGS
id int
booked_object_id int
date_from date
date_tom date

This table has about 10k records with booked objects.

Now in one of my PHP function I have array with new data, which I want to insert into this table. There are about 20-30 new bookings to insert when my function is executed.

Now let's get to my main problem - I want it to check if ANY of bookings which I want to insert into table is already booked (object_id and date_from is the same as in my php array). If any of it is already booked, my function will not insert anything new into table.

Is there a more efficient way than getting all contents of mysql table into PHP array and check it 20 times (or number of my inserts)?

Answer 1

If you are planning on looking up a certain column in your table then you should index it. This will create a hashtable that the db-server will use to lookup rows.

And as for the efficiency of making 20 calls.. you could use an IN statement to select all existing records in 1 call and simply ignore the already existing ones when inserting.

reference:

expr IN (value,...)