Group by Clause and Aggregated function in SQL || Steem Alliance Community.

Hello Everyone,

How are you, i hope you guys will happy and well. By thre grace of God, i am also well. Today i am here with new post of SQL and PL/SQL series in which i am going to discuss about Distinct key word and order by clause.

Group by clause is basically used with aggregate functions. first of all, we will discuss about aggregate function. then we will move on group by clause. there are many types of aggregate functions that are used in our daily routine development in sql.

Aggregated functions:

• Sum()
• Avg()
• min()
• max()
• count()

First of all we i will share th output of a table b using simple select statement.

NO	sector	cust_id	name_1	Town
1	1000	4270603	SIKANDAR	PESHAWAR
2	1000	4270939	TARIQ	ALI PUR
3	1000	5715170	ALI HAMZA	GALA YOUSAF
4	1000	7796882	IMRAN	KHANEWAL
5	1000	953045	UMAR	YAZMAN
6	1000	953045	UMAR	YAZMAN

If we want to count the total rows of tables then we will use the count() function. below is the query for table data counting.

select count(cust_id) from users

Result of query.

count(cust_id)
6

To calculate the total value of a particular column within a table, the SUM() function will use. Below is the query for aggregating table data using this function.

select sum(cust_id) from users

Result of query.

sum(cust_id)
23959684

To find the minimum values from a particular column within a table then the min() function will use. Below is the query for aggregating table data using this function.

select min(cust_id) from users

Result of query.

min(cust_id)
953045

Img SRC

I hope things will clear now we move on group by function. group by clause is used to get the result of data from table on group based on depending on the values in one or more columns.

select sum(cust_id) , sector  from users group by sector

Result of query.

sector of each row is same so it will sum the cust_id on the base of sector. same sector will group by and then sum function will apply on it and then show the result.

sum(cust_id)	sector
23959684	1000

Now we will apply the group by function on the base of two colums then see the result.

select sum(cust_id) , sector , name_1 from users group by sector , name_1

Result of query:

NO	sector	cust_id	name_1
1	1000	4270603	SIKANDAR
2	1000	4270939	TARIQ
3	1000	5715170	ALI HAMZA
4	1000	7796882	IMRAN
5	1000	1906090	UMAR

In the preceding outcome, I utilized the sum() function with the group by clause to aggregate the cust_id values. The group by function was applied based on the sector and name_1 columns. While the sector remains same across all rows, the name_1 values differ. the data 'Umar' in name_1 appears twice with the same sector, so the group by function will add up these two lines.

It would be my pleasure if you will share your opinion and reviews on this topic

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