Use of MySQL Notes function Query

Reference Table

Count () is used to count the number of records
Copy codeThe Code is as follows:
Mysql> select count (*) from score;
Mysql> select count (*) from score where stu_id = 901;

Sum () summation Function
Copy codeThe Code is as follows:
Mysql> select sum (grade) from score;
Mysql> select id, sum (grade) from score where stu_id = 901;

Avg () averaging Function
Copy codeThe Code is as follows:
Mysql> select avg (grade) from score where c_name = 'compute ';
Mysql> select c_name, avg (grade) from score group by c_name;


Max () returns the maximum value.
Copy codeThe Code is as follows:
Mysql> select c_name, max (grade) from score where c_name = 'English ';
Mysql> select c_name, max (grade) from score group by c_name;


Min () Evaluate the minimum Function
Copy codeThe Code is as follows:
Mysql> select c_name, min (grade) from score where c_name = 'Chinese ';
Mysql> select c_name, min (grade) from score group by c_name;


Concat concatenation Function
Copy codeThe Code is as follows:
Mysql> select Concat (c_name, '(', stu_id ,')')
-> From score order by stu_id;