FROM clause is used to specify table name from which we are trying to fetch data using the SELECT statement. FROM clause is also used to specify subquery. More than one table can be directly specified by separating with a comma (,) using FROM clause. While executing the query, system first validates the FROM clause rather than checking SELECT or DELETE statement.

FROM table1
[ { INNER JOIN 
   | LEFT [OUTER] JOIN
   | RIGHT [OUTER] JOIN
   | FULL [OUTER] JOIN } table2
 ON table1.column1 = table2.column1 ];

• table1 – Specifies the name of the table1.
• table2 - Specifies the name of the table2.

consider employee_details and department_details tables are as follows -

Scenario – Fetch details from table.

Requirement – Fetch sales department employee details. The query was as follows –

 SELECT emp_name FROM employee_details WHERE dept_id = "2000"; 

By executing above query, we can get results as shown below –

Scenario – Fetch matching details from both tables using Subquery.

Requirement – Fetch employees working in location1 from employee_details table. The query was as follows –

SELECT emp_id, emp_name, salary, dept_id FROM employee_details
WHERE dept_id 
IN (SELECT dept_id FROM department_details WHERE dept_location =
 'Location1'); 

By executing above query, we can get results as shown below -

Scenario – Fetch matching details from both tables using INNER JOIN.

Requirement – Fetch emp_id, emp_name, salary from employee_details and their corresponding dept_location from department_details tables. The query was as follows –

SELECT employee_details.emp_name, employee_details.emp_id,
employee_details.Salary, department_details.dept_location
FROM employee_details INNER JOIN department_details ON 
employee_details.dept_id = department_details.dept_id; 

By executing above query, we can get results as shown below –

Scenario – Fetch matching details from both tables using OUTER JOIN.

Requirement1– Fetch emp_id, emp_name, salary from employee_details and their corresponding dept_name from department_details tables. The query was as follows –

SELECT employee_details.emp_name, employee_details.emp_id,
employee_details.salary, department_details.dept_name
FROM employee_details LEFT OUTER JOIN department_details
ON employee_details.dept_id = department_details.dept_id;  

By executing above query, we can get results as shown below -

Requirement2 – Fetch emp_id, emp_name, salary from employee_details and their corresponding dept_name from department_details tables. The query was as follows –

SELECT employee_details.emp_name, employee_details.emp_id,
employee_details.Salary, department_details. dept_name 
FROM employee_details RIGHT OUTER JOIN department_details
ON employee_details.dept_id = department_details.dept_id; 

By executing above query, we can get results as shown below –