Mega Code Archive
Calculate the overall average and save it in a variable, then compare each drivers average to the saved value
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using a HAVING clause
mysql>
mysql>
mysql> CREATE TABLE mytable
-> (
-> rec_id INT UNSIGNED NOT NULL AUTO_INCREMENT,
-> name VARCHAR(20) NOT NULL,
-> trav_date DATE NOT NULL,
-> miles INT NOT NULL,
-> PRIMARY KEY (rec_id)
-> );
Query OK, 0 rows affected (0.01 sec)
mysql>
mysql> INSERT INTO mytable (name,trav_date,miles)
-> VALUES
-> ('Ben','2010-11-30',152),
-> ('Suzi','2010-11-29',391),
-> ('Henry','2010-11-29',300),
-> ('Henry','2010-11-27',96),
-> ('Ben','2010-11-29',131),
-> ('Henry','2010-11-26',115),
-> ('Suzi','2010-12-02',502),
-> ('Henry','2010-12-01',197),
-> ('Ben','2010-12-02',79),
-> ('Henry','2010-11-30',203)
-> ;
Query OK, 10 rows affected (0.00 sec)
Records: 10 Duplicates: 0 Warnings: 0
mysql>
mysql> SELECT @overall_avg := AVG(miles) FROM mytable;
+----------------------------+
| @overall_avg := AVG(miles) |
+----------------------------+
| 216.600000000 |
+----------------------------+
1 row in set (0.00 sec)
mysql> SELECT name, AVG(miles) AS driver_avg FROM mytable
-> GROUP BY name
-> HAVING driver_avg < @overall_avg;
+-------+------------+
| name | driver_avg |
+-------+------------+
| Ben | 120.6667 |
| Henry | 182.2000 |
+-------+------------+
2 rows in set (0.00 sec)
mysql>
mysql> drop table mytable;
Query OK, 0 rows affected (0.00 sec)
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