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Suppose Table1 contains column orderid (not a key, although it’s NOT NULL and unique). It contains 5-digit numbers.
What’s the best way to generate a php var $unique_var that is not in that column.
What could be important, from 10% to 30% of 5-digit numbers are in the table (so generating a number and checking while (mysql_num_rows() ==0) {} is not a best way to find one, are there any better solution for performance?).
Thank you.
If there is just 10-30% of numbers already taken – then it means that only 10-30% of queries will be performed at least twice. Which is not a big performance issue at all.
Otherwise – just create all-5-digit-numbers-list table (just 100k rows) and remove all that exist. When you need another random number – just pick one and delete.