Generating Unique Table Names
Problem
You need to create a table with a name that is guaranteed not to exist already.
Solution
If you can create a
TEMPORARY table, it doesn’t
matter if the name exists already. Otherwise, try to generate a value
that is unique to your client program and incorporate it into the
table name.
Discussion
MySQL is a multiple-client database server, so if a given script that
creates a transient table might be invoked by several clients
simultaneously, you must take care to keep multiple invocations of
the script from fighting over the same table name. If the script
creates tables using
CREATE TEMPORARY
TABLE, there is no problem because different
clients can create temporary tables having the same name without
clashing.
If you can’t use CREATE
TEMPORARY TABLE because the
server version is older than 3.23.2, you should make sure that each
invocation of the script creates a uniquely named table. To do this,
incorporate into the name some value that is guaranteed to be unique
per invocation. A timestamp won’t work, because
it’s easily possible for two instances of a script
to be invoked within the same second. A random number may be somewhat
better. For example, in Java, you can use the
java.util.Random( ) class to create a table name
like this:
import java.util.Random; import java.lang.Math; Random rand = new Random ( ); int n = rand.nextInt ( ); // generate random number n = Math.abs (n); // take absolute value String tblName = "tmp_tbl_" + n;
Unfortunately, ...