I started by googling and found the article How to write INSERT if NOT EXISTS queries in standard SQL which talks about mutex tables.
I have a table with ~14 million records. If I want to add more data in the same format, is there a way to ensure the record I want to insert does not already exist without using a pair of queries (i.e., one query to check and one to insert is the result set is empty)?
unique constraint on a field guarantee the
insert will fail if it's already there?
It seems that with merely a constraint, when I issue the insert via PHP, the script croaks.