The file examples/pdb/mysql/mysql.dump in the source distribution
needs some improvements.  First of all, it's missing the definition
for the logon_hours column.  This must have been recently added to
the SQL backend.  As well, the uid column is defined as the primary
key, even though this column (as well as the gid column) is never read
or written by the SQL backend.  The columns that are used for selects
and updates by keys are not indexed.  I've remedied all of these failings
in the file samba.sql, which can be obtained by anonymous FTP at
ftp.cc.umanitoba.ca in the source directory.