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SQL Server Create View

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Publicado em: 05/08/2025

SQL Server Views: A Comprehensive Guide

This article provides a comprehensive guide to creating and using views in SQL Server. Views are virtual tables based on the result-set of an SQL statement. They simplify complex queries, enhance data security, and improve code maintainability. This guide will walk you through the creation, usage, and benefits of SQL Server views.

Fundamental Concepts / Prerequisites

Before diving into creating views, you should have a solid understanding of the following concepts:

  • Basic SQL Syntax: Knowledge of SELECT statements, WHERE clauses, JOIN operations, and other fundamental SQL concepts is crucial.
  • SQL Server Database: A working SQL Server environment and access to a database are necessary to execute the examples.
  • Table Structures: Understanding the structure of the tables you'll be querying with the view is essential.

Creating Views in SQL Server

The CREATE VIEW statement is used to create a view in SQL Server. The syntax is as follows:


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

-- Example: Create a view that shows only active customers
CREATE VIEW ActiveCustomers AS
SELECT CustomerID, FirstName, LastName, Email
FROM Customers
WHERE IsActive = 1;

Code Explanation

The code snippet demonstrates the creation of a view named ActiveCustomers. Let's break it down:

CREATE VIEW ActiveCustomers: This statement initiates the creation of a view named ActiveCustomers.

AS: This keyword signifies that the following SQL statement will define the view's content.

SELECT CustomerID, FirstName, LastName, Email FROM Customers: This SELECT statement retrieves specific columns (CustomerID, FirstName, LastName, and Email) from the Customers table.

WHERE IsActive = 1: This WHERE clause filters the results to include only customers where the IsActive column is equal to 1 (representing active customers).

Complexity Analysis

The complexity of creating a view is primarily dependent on the complexity of the underlying SQL query. The view itself doesn't store data; it's merely a stored query definition.

Time Complexity: The time complexity of executing a query that uses a view is equal to the complexity of executing the view's underlying SELECT statement, plus the overhead of processing the results that the view returns. If the view's query involves joins, subqueries, or complex filtering, the time complexity will be accordingly higher (e.g., potentially O(n*m) for joins, O(n^2) for correlated subqueries in the worst case, etc.). The CREATE VIEW statement itself has a time complexity that is largely determined by the query parsing, optimization, and storage of the view definition, typically considered to be O(1) or very close to it.

Space Complexity: The space complexity is relatively low. SQL Server stores the view definition (the SQL query) and metadata associated with the view, such as column names and data types. The actual data is not duplicated; the view simply references the underlying tables. Therefore, the space complexity is primarily related to the size of the query definition itself, which is typically negligible compared to the data stored in the underlying tables. This could be considered O(1) as the storage needed for the view definition is constant.

Alternative Approaches

One alternative to using views is to use stored procedures. A stored procedure is a precompiled collection of SQL statements stored under a name and processed as a unit. A stored procedure can encapsulate complex logic and can accept parameters, making them more flexible than simple views. However, stored procedures are generally used for data manipulation and complex business logic, while views are better suited for simplifying data retrieval and providing a specific, filtered perspective on the underlying data. Another approach is to directly embed the SQL query in your application code, but this leads to code duplication and makes it harder to maintain the query logic. Materialized views also exist in some database systems (not in standard SQL Server), where the result of the view's query is physically stored, offering potentially faster read performance at the cost of increased storage and maintenance overhead.

Conclusion

Views are powerful tools in SQL Server for simplifying queries, enhancing data security, and improving code maintainability. By creating views, you can abstract away complex SQL statements and provide a more user-friendly interface for accessing data. Understanding the syntax and best practices for creating and using views is an essential skill for any SQL Server developer.