Group By VS Distinct in SQL

Group by VS Distinct

Group By : The SQL GROUP BY statement is used together with the SQL aggregate functions to group the retrieved data by one or more columns. 

Distinct : The DISTINCT keyword can be used to return only distinct (different) values.

Orders table :

OrderId	PersonName	Price	Quantity
101	John	12	1
102	Sam	4	1
103	John	14	2
104	Brendon	12	1
106	Allen	2	11
107	Allen	3	11

Query 1: Select PersonName,Price from Orders group by PersonName,Price

Query 2:Select distinct PersonName,Price from Orders

Execution plan for both queries are same and return 5 records.

But the purpose of Group by is different it is used to group the records and apply aggregate function on it.

Query 3: Select PersonName,Sum(Price) as ‘Total’ from Orders group by PersonName

Query 3 returns only for records like below

PersonName	Total
Allen	5
Brendon	12
John	26
Sam	4

Distinct in SQL

Distinct : The DISTINCT keyword can be used to return only distinct (different) values.

Orders table :

OrderId	PersonName	Price	Quantity
101	John	12	1
102	Sam	4	1
103	John	14	2
104	Brendon	12	1
106	Allen	2	11
107	Allen	2	11

Query 1:Select distinct PersonName from Orders

Query 2:Select distinct PersonName,Price from Orders

Query 1 : Even though price is different we used ‘distinct’ only on PersonName so it return only 4 records.

Query2 : Return 4 rows because Allen is repeated twice with same price so it returns Allen only Once

SQL Group By

Group By in SQL:

The SQL GROUP BY statement is used together with the SQL aggregate functions to group the retrieved data by one or more columns. 

Example :

Sales(OrderId,Customer,Price,Date)

1.Select Customer,sum(price) from Sales group by Customer

What is SQL Server datatypes?

Datatype is an attribute which specifies what type of data you can store in an object.

Like any other RDBMS and programming language SQL Server uses datatype's to specify type of the data can be store in local variables,expressions,parameters and each column data.

Example:

Numeric types : int,tiny int,big int,float,decimal etc

Character types : Char,Varchar,Text etc

10 common questions about SQL Server datatypes

What is SQL Server?

SQL Server is Relational Database Management System ( RDBMS),which responds to SQL queries originated from the client machine.

RDBMS : Relational database groups data by using common characteristics.
SQL Queries : Declarative code used to Insert,update and delete data in a RDBMS database.