How to create a view in SQL

A view is a virtual table in SQL that derives data from the underlying table. The steps to create a view include: use the CREATE VIEW statement to specify the view name and the columns selected from the underlying table. Optionally specify connections between the underlying tables and application filters. Views simplify queries, enhance data security, improve performance, and abstract the underlying table structure.

How to create a view using SQL

definition:
A view is a virtual table in SQL that derives data from one or more underlying tables. It is different from a table because it does not store the actual data, but retrieves and displays the data from the underlying table as needed.

Steps to create a view:

1. Create a view statement

Create a view using the CREATE VIEW statement. The syntax of this statement is as follows:

 <code class="sql">CREATE VIEW [schema_name.]view_name AS SELECT column1, column2, ... FROM table1 [JOIN table2 ON ...] [WHERE condition]</code>

2. Specify the view name

view_name is the name of the view you want to create. View names should follow the same naming convention as table names.

3. Select the column to display

The SELECT clause specifies the column to be selected from the underlying table. You can only select columns that exist in the underlying table.

4. Specify the basic table

The FROM clause specifies the underlying table to be used to create the view.

5. Use connection (optional)

If the view derives data from multiple tables, you can use the JOIN clause to concatenate them.

6. Apply filters (optional)

The WHERE clause can be used to apply a filter and returns only rows that meet the specified criteria.

Example:

Create a view named customer_view that contains customer_id , name , and email columns of the client table:

 <code class="sql">CREATE VIEW customer_view AS SELECT customer_id, name, email FROM customers;</code>

advantage:

• Simplified queries: Views can simplify complex queries that are frequently executed.
• Data Security: Views can limit access to sensitive data.
• Improved performance: Views can improve performance for frequent queries because it avoids multiple access to the underlying tables.
• Data abstraction: Views can hide the complexity of the underlying table structure, making queries easier to write.

The above is the detailed content of How to create a view in SQL. For more information, please follow other related articles on the PHP Chinese website!