///check the number of connections to database
netstat -antp | grep :3306 | wc -l

The HAVING clause was added to SQL because the WHERE clause could not be used with aggregate functions.

Syntax:

SELECT column_name, aggregate_function(column_name)
FROM table_name
WHERE column_name operator value
GROUP BY column_name
HAVING aggregate_function(column_name) operator value

Example:
SELECT customer,SUM(orderprice) FROM trans_orders
GROUP BY customer
HAVING SUM(orderprice)<1000

ALTER TABLE `listing` ADD INDEX `idx_uid_type` ( `uid` , `listing_type` ) ;
ALTER TABLE `users` ADD INDEX ( `email` ) ;

ALTER TABLE `listing_reply` ADD INDEX ( `listingid` , `uid` , `parent_listing` ) ;

select video_file from videos INTO OUTFILE ‘/tmp/video1.txt’;

Query Above exports all the rows for coulmn video_file into a text file “/tmp/video1.txt” .

DB_LIST=”$(mysql -u root -Bse ’show databases’ | egrep -v ‘information_schema|mysql|test’)”
for db in ${DB_LIST[@]}
do
TABLENAMES=”$(mysql -u root $db -Bse ’show tables’)”
echo “Database: “$db
for TABLENAME in ${TABLENAMES[@]}
do
mysql -u root $db -Bse “optimize TABLE $TABLENAME;”
echo $TABLENAME” table has been optimized”
done
echo $db – $TABLENAME “Optimized has been completed”
done
echo “All Databases have been successfully Optimized”

DB_LIST=”$(mysql -u root -Bse ’show databases’ | egrep -v ‘information_schema|mysql|test’)”
for db in ${DB_LIST[@]}
do
TABLENAMES=”$(mysql -u root $db -Bse ’show tables’)”
echo “Database: “$db
for TABLENAME in ${TABLENAMES[@]}
do
mysql -u root $db -Bse “Analyze TABLE $TABLENAME;”
echo $TABLENAME “Analyze has been done”
done
echo $db – $TABLENAME “Analyzis has been completed”
done
echo “All Databases have been successfully Optimized”