Question

I want to know that my sql execute count queries in linear time or in log(n) time i think that if query parameter was indexed it can do it by cubing

Answer 1

• MyISAM will return immediatelly.
• InnoDB will do PK scan, so time will lineary increase with number of records.

If you need to see approximately how many records InnoDB table holds, the fastest way is using

EXPLAIN select * from student;

(but innodb statistics may be wrong, so 40% error is quite possible also)