Question

Using Ruby DBI, how can I check if a record set is empty? (without iterating through it or doing a count query)

sth = dbh.prepare("select * from things WHERE created_at > '#{start}'")
sth.execute

Answer 1

You could always just ask the result object:

res = sth.execute
res.num_rows

The operation will have to pull down all matching records, though, so if you only need a count, you might want to select that directly.

Also escape your SQL. You cannot just put arbitrary strings in there. This is better:

sth = dbh.prepare("select * from things WHERE created_at > '%s'" % sth.escape_string(start))