In Oracle GROUP BY clause is used with SELECT statement to collect data from multiple records and group the results by one or more columns.

Syntax:

SELECT expression1, expression2, ... expression_n,   
aggregate_function (aggregate_expression)  
FROM tables  
WHERE conditions  
GROUP BY expression1, expression2, ... expression_n;   

Parameters:

expression1, expression2, ... expression_n: It specifies the expressions that are not encapsulated within aggregate function. These expressions must be included in GROUP BY clause.

aggregate_function: It specifies the aggregate functions i.e. SUM, COUNT, MIN, MAX or AVG functions.

aggregate_expression: It specifies the column or expression on that the aggregate function is based on.

tables: It specifies the table from where you want to retrieve records.

conditions: It specifies the conditions that must be fulfilled for the record to be selected.

Oracle GROUP BY Example: (with SUM function)

Let's take a table "salesdepartment"

Salesdepartment table:

CREATE TABLE  "SALESDEPARTMENT"   
   (    "ITEM" VARCHAR2(4000),   
    "SALE" NUMBER,   
    "BILLING_ADDRESS" VARCHAR2(4000)  
   )  
/  

Execute this query:

SELECT item, SUM(sale) AS "Total sales"  
FROM salesdepartment  
GROUP BY item;  

Output

The above example will show the total sales of every individual item.

Oracle GROUP BY Example: (with COUNT function)

Let's take a table "customers"

Here we are creating a table named customers. This table doesn't have any primary key.

Customer table:

CREATE TABLE  "CUSTOMERS"   
   (    "NAME" VARCHAR2(4000),   
    "AGE" NUMBER,   
    "SALARY" NUMBER,   
    "STATE" VARCHAR2(4000)  
   )  
/  

Execute this query:

SELECT state, COUNT(*) AS "Number of customers"  
FROM customers  
WHERE salary > 10000  
GROUP BY state;  

Output:

Oracle GROUP BY Example: (with MIN function)

Let?s take a table "employees"

Employees table:

CREATE TABLE  "EMPLOYEES"   
   (    "EMP_ID" NUMBER,   
    "NAME" VARCHAR2(4000),   
    "AGE" NUMBER,   
    "DEPARTMENT" VARCHAR2(4000),   
    "SALARY" NUMBER  
   )  
/  

Execute this query:

SELECT department,   
MIN(salary) AS "Lowest salary"  
FROM employees  
GROUP BY department;  

Output:

Oracle GROUP BY Example: (with MAX function)

In this example, we are using "employees" table that is given above.

Execute this query:

SELECT department,  
MAX(salary) AS "Highest salary"  
FROM employees  
GROUP BY department;  

Output: