Can you check out the total number of records in each column, how to deal with

Can you check out the total number of records in each column
MySQL has a field in a table: class_id

class_id
1
1
2
2
2
5
3
3
......

How to query once (or efficiently) to get the total number of records in each column. That
The records of class_id 1 were 2, 2 were 3, 5 were 1, 3 were 2, ...



------Solution--------------------

PHP Code

Create tablecreate TABLE ' demo ' (  ' demoid ' int (one) not null auto_increment,  ' class_id ' int (one) ' DEFAULT NULL,  PRIMARY KEY (' demoid ')) Engine=myisam auto_increment=8 DEFAULT CHARSET=UTF8//2 input test Data//3 Query Select COUNT (class_id), class _id from demo GROUP by class_id
