Given this table, I want to count the number of distinct targetranges.
CREATE TABLE job (
job_id int(10) unsigned NOT NULL auto_increment,
customer_id int(10) unsigned NOT NULL default '0',
scanner_id int(10) unsigned NOT NULL default '0',
status_id int(10) unsigned NOT NULL default '0',
changed timestamp(14) NOT NULL,
targetrange char(255) default NULL,
force_exit tinyint(1) unsigned NOT NULL default '0',
PRIMARY KEY (job_id),
KEY status_id (status_id)
) TYPE=InnoDB;
I tried "select distinct targetrange from job;" and I do get "273" rows.
But I would have to use PHP's mysql_num_rows() to get that. I don't need
all the rows returned however, just the count(), so I think this method
is wasteful and probably will get slower as the db fills up with
millions of rows.
mysql> select count(1) from job;
+----------+
| count(1) |
+----------+
| 351 |
+----------+
Is more of what I want, but how do I combine that with DISTINCT to get
something like:
+----------+
| count(1) |
+----------+
| 273 |
+----------+
And also, should I make targetrange an index too to help speed up the
query or will it not matter?
