Day 44 – SQL CREATE VIEW Statement
In SQL, a view is a virtual table that is based on the result of a SQL SELECT statement. Views can be used to simplify complex queries, provide a customized view of the data, or restrict access to sensitive data. The CREATE VIEW statement is used to create a new view in a database.
The basic syntax for creating a view in SQL is as follows:
CREATE VIEW view_name AS
SELECT column1, column2, ...
FROM table_name
WHERE condition;
In the above syntax, view_name is the name of the view, column1, column2, etc. are the columns to include in the view, table_name is the name of the table to use in the SELECT statement, and condition is an optional WHERE clause to filter the results.
For example, let’s say we have a table named “employees” with columns “employee_id”, “first_name”, “last_name”, “hire_date”, and “salary”. We want to create a view that includes only the “employee_id”, “first_name”, “last_name”, and “hire_date” columns. The CREATE VIEW statement for this view would be as follows:
CREATE VIEW employee_info AS
SELECT employee_id, first_name, last_name, hire_date
FROM employees;
In the above example, we have created a view named “employee_info” that includes the “employee_id”, “first_name”, “last_name”, and “hire_date” columns from the “employees” table.
Once a view is created, it can be used like a regular table in SQL SELECT statements. For example, to retrieve all rows from the “employee_info” view, we could use the following SELECT statement:
SELECT * FROM employee_info;
In the above example, we are selecting all columns from the “employee_info” view.
It is important to note that views do not store data themselves, but instead provide a virtual representation of the data based on the underlying SELECT statement. Views can be a powerful tool for simplifying queries and managing access to data, but they can also have performance implications if used improperly.