freeCodeCamp/guide/english/sql/sql-replace-view-statement/index.md

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SQL Replace VIEW Statement

SQL Replace VIEW Statement

Introduction

A View is a database object that presents data from in one or more tables. The same SQL statement used to create a view can also be used to replace an existing view.

This guide will update (replace) the existing view "programming-students-v" with one that is slightly different and has a different name.

Safety tip: always backup the schema before making changes to it.

General sytax

CREATE OR REPLACE VIEW view_name AS
SELECT column1, column2, ...
FROM table_name
WHERE condition;

SQL Used to create the view and the current data

create view `programming-students-v` as
select FullName, programOfStudy 
from student 
where programOfStudy = 'Programming';

select * from `programming-students-v`;

Current Data:

+-----------------+----------------+
| FullName        | programOfStudy |
+-----------------+----------------+
| Teri Gutierrez  | Programming    |
| Spencer Pautier | Programming    |
| Louis Ramsey    | Programming    |
| Alvin Greene    | Programming    |
| Sophie Freeman  | Programming    |
+-----------------+----------------+
5 rows in set (0.00 sec)

A list of the existing views:

SHOW FULL TABLES IN fcc_sql_guides_database WHERE TABLE_TYPE LIKE 'VIEW';

+-----------------------------------+------------+
| Tables_in_fcc_sql_guides_database | Table_type |
+-----------------------------------+------------+
| programming-students-v            | VIEW       |
| students-contact-info_v           | VIEW       |
| students_dropme_v                 | VIEW       |
+-----------------------------------+------------+
3 rows in set (0.00 sec)

Replacing the view

create or replace view `programming-students-v` as
select FullName, programOfStudy, sat_score 
from student 
where programOfStudy = 'Programming';    

select * from `programming-students-v`;

Note: the view now shows the sat_score.

+-----------------+----------------+-----------+
| FullName        | programOfStudy | sat_score |
+-----------------+----------------+-----------+
| Teri Gutierrez  | Programming    |       800 |
| Spencer Pautier | Programming    |      1000 |
| Louis Ramsey    | Programming    |      1200 |
| Alvin Greene    | Programming    |      1200 |
| Sophie Freeman  | Programming    |      1200 |
+-----------------+----------------+-----------+

Note: the list of views hasn't change, our view is replaced.

mysql>  SHOW FULL TABLES IN fcc_sql_guides_database WHERE TABLE_TYPE LIKE 'VIEW';
+-----------------------------------+------------+
| Tables_in_fcc_sql_guides_database | Table_type |
+-----------------------------------+------------+
| programming-students-v            | VIEW       |
| students-contact-info_v           | VIEW       |
| students_dropme_v                 | VIEW       |
+-----------------------------------+------------+
3 rows in set (0.00 sec)

*As with all of these SQL things there is MUCH MORE to them than what's in this introductory guide. I hope this at least gives you enough to get started. Please see the manual for your database manager and have fun trying different options yourself.