We can use sql HAVING command to add condition to the query. The advantage of using HAVING command is it can be used in aggregate functions like count, max etc. We can't use SQL WHERE clause here. This way we can add value to our select command as per requirement. Usually SQL HAVING command is used in conjunction with group by command. Please read the sql group by command and SQL sub group by command to know more about grouping the records.
Here is the full table with all the rows. On this we will apply the group by query
d_id
name
type
category
price
stock
1
Book1
Book
Management
220
10
2
Book2
CD
Management
120
8
3
Book3
Report
Management
25
4
4
Book4
Book
Management
55
8
5
Document1
Book
Management
15
23
6
Document2
CD
Computers
80
45
7
Document3
Report
Computers
55
65
8
Book5
Report
Management
80
10
9
Document4
CD
Management
72
5
10
Book 8
Book
Computers
88
6
11
Book 9
CD
Computers
100
5
12
Document5
Report
Computers
85
8
13
Book 10
Book
Computers
150
5
Here is the SQL having command with group by command applied on the above table.
SELECT category, type , count( * ) as total FROM `documents` GROUP BY category, type HAVING total < 3
This will display the total records in each group and sub group. Like this