The SELECT command of SQL is used to retrieve data from the tables of the
database and display those data in a table format.
The general
form of SELECT statement is as shown
below:
|
SELECT department_id, employee_id, first_name
FROM employees
WHERE department_id=60;
|
WHERE clause usage:
The WHERE clause is used to restrict the
rows returned by SELECT statement. It
helps to filter the data as per your requirement.
The general form of
select statement that limits the retrieval of data by using WHERE clause is as shown below:
|
SELECT *||([DISTINCT] column||expression
[alias],...)
FROM tableName
WHERE condition();
|
The WHERE clause is placed right after FROM clause as you can see in the above
general form.
Consider the below SQL
query used to retrieve data from EMPLOYEE
table:
|
SELECT department_id, employee_id, first_name
FROM employees;
|
The output of the
above query is as shown below:
Now let us use WHERE
clause to filter the data as per our requirement. Suppose my requirement is to
get data only for department_id=60, in that
case I can modify above SQL query as shown below:
|
SELECT department_id, employee_id, first_name
FROM employees
WHERE department_id=60;
|
The output of the above query is as shown below:
You can see in the above query result, only data for department_id=60 is present.
