Select - (Oracle Query)

The SELECT statement is used in Oracle to retrieve data from one or more tables in a database. It allows you to specify the columns you want to retrieve, the table(s) you want to retrieve them from, and any filters or sorting criteria you want to apply.

Syntax

The basic syntax of the SELECT statement in Oracle is as follows:

SELECT column1, column2, ...
FROM table_name
WHERE condition
ORDER BY column_name [ASC|DESC];

Here, column1, column2, etc. are the columns you want to retrieve, separated by commas. table_name is the name of the table(s) you want to retrieve the columns from. condition is an optional filter expression that limits the rows returned based on some criteria. column_name is the name of the column you want to order the results by, and ASC|DESC specifies whether you want to sort the results in ascending or descending order.

Example

Here is an example of a SELECT statement that retrieves employee information from an Employee table in an Oracle database:

SELECT employee_id, last_name, first_name, hire_date
FROM Employee
WHERE department_id = 10
ORDER BY hire_date DESC;

This statement retrieves the employee_id, last_name, first_name, and hire_date columns from the Employee table, but only for employees that belong to the department with department_id equal to 10. The results are sorted in descending order by hire_date.

Output

The output of a SELECT statement in Oracle is a set of rows that match the specified criteria, sorted according to the order specified in the ORDER BY clause (if provided).

Explanation

In the above example, we are selecting certain columns from the Employee table where the department_id is equal to 10. We are only selecting the employee_id, last_name, first_name, and hire_date columns, which will be returned for all matching rows. The ORDER BY clause is used to sort the results in descending order by hire_date.

Use

The SELECT statement is the fundamental building block of SQL, used to retrieve data from one or more tables in an Oracle database. It can be used to retrieve specific columns or all columns from a table, filter rows based on specific criteria, and sort the results in a specific order.

Important Points

• The SELECT statement is used to retrieve data from one or more tables in an Oracle database.
• It allows you to specify the columns you want to retrieve, the table(s) you want to retrieve them from, and any filters or sorting criteria you want to apply.
• The WHERE clause is used to filter the rows returned based on some criteria.
• The ORDER BY clause is used to sort the results in ascending or descending order.

Summary

In summary, the SELECT statement in Oracle is used to retrieve data from one or more tables in a database. It allows you to specify the columns you want to retrieve, the table(s) you want to retrieve them from, and any filters or sorting criteria you want to apply. The WHERE clause is used to filter the rows returned based on some criteria, and the ORDER BY clause is used to sort the results in ascending or descending order.