DROP TABLE IF EXISTS t1,t2;
CREATE TABLE t1 (
ID int(11) NOT NULL auto_increment,
NAME varchar(75) DEFAULT '' NOT NULL,
LINK_ID int(11) DEFAULT '0' NOT NULL,
PRIMARY KEY (ID),
KEY NAME (NAME),
KEY LINK_ID (LINK_ID)
);
INSERT INTO t1 (ID, NAME, LINK_ID) VALUES (1,'Mike',0);
INSERT INTO t1 (ID, NAME, LINK_ID) VALUES (2,'Jack',0);
INSERT INTO t1 (ID, NAME, LINK_ID) VALUES (3,'Bill',0);
CREATE TABLE t2 (
ID int(11) NOT NULL auto_increment,
NAME varchar(150) DEFAULT '' NOT NULL,
PRIMARY KEY (ID),
KEY NAME (NAME)
);
SELECT DISTINCT
t2.id AS key_link_id,
t2.name AS link
FROM t1
LEFT JOIN t2 ON t1.link_id=t2.id
GROUP BY t1.id
ORDER BY link;
key_link_id	link
NULL	NULL
drop table t1,t2;
CREATE TABLE t1 (
html varchar(5) default NULL,
rin int(11) default '0',
out int(11) default '0'
) TYPE=MyISAM;
INSERT INTO t1 VALUES ('1',1,0);
SELECT DISTINCT html,SUM(out)/(SUM(rin)+1) as 'prod' FROM t1 GROUP BY rin;
html	prod
1	0.00
drop table t1;