What is a storage engine? What are the differences between innodb and myisam eng

mysql> select * from store; +------+-------+-------+ | id | month | sales | +------+-------+-------+ | 1 | 1 | 100 | | 1 | 2 | 100 | | 1 | 3 | 200 | | 1 | 4 | 300 | | 1 | 5 | NULL | | 1 | 6 | 200 | | 1 | 7 | 800 | | 1 | 8 | 100 | | 1 | 9 | 240 | | 1 | 10 | 140 | | 1 | 11 | 400 | | 1 | 12 | 300 | | 2 | 1 | 300 | | 2 | 2 | 300 | | 2 | 3 | 300 | | 2 | 4 | 200 | | 2 | 5 | 200 | | 2 | 6 | 200 | | 2 | 7 | 100 | | 2 | 8 | 100 | | 2 | 9 | 300 | | 2 | 10 | 100 | | 2 | 11 | 150 | | 2 | 12 | 150 | +------+-------+-------+ this is my table. i need to display output like this. +------+----------+----------+----------+----------+ | id | quarter1 | quarter2 | quarter3 | quarter4 | +------+----------+----------+----------+----------+ | 1 | 400 | 500 | 1140 | 840 | | 2 | 900 | 600 | 500 | 400 | +------+----------+----------+----------+----------+ what single query i have to write for this. i tried this query and it displays like the below mysql> select id,sum(sales) as quarter1,(select sum(sales) from store where mont h>3 and month<7 ) as quarter2,(select sum(sales) from store where month>6 and mo nth<10)as quarter3 from store where month>0 and month<4 group by id; +------+----------+----------+----------+ | id | quarter1 | quarter2 | quarter3 | +------+----------+----------+----------+ | 1 | 400 | 1100 | 1640 | | 2 | 900 | 1100 | 1640 | +------+----------+----------+----------+ 2 rows in set (0.00 sec) tel me how to rectify it.

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Write a query to fetch duplicate records from a table using mysql?

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Define REGEXP?

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