Understanding DB2 Views and Their Benefits | Generated by AI
Question: What is a view in DB2, and why do we use views?
Answer:
A view in DB2 is a virtual table (also called a named query) that represents the result of a stored SELECT statement. It is not a physical table and does not store any data itself. When you query a view, DB2 executes the underlying SELECT statement against the base tables (one or more real tables or even other views) and returns the result as if it were a real table.
Basic Syntax to Create a View
CREATE VIEW view_name [(column_list)]
AS
SELECT_statement
[WITH [CASCADED | LOCAL] CHECK OPTION];
Example:
CREATE VIEW active_employees AS
SELECT emp_id, first_name, last_name, department, hire_date
FROM employees
WHERE status = 'ACTIVE'
AND hire_date > '2020-01-01';
Main Reasons to Use Views in DB2
Views are widely used because they provide several important benefits:
-
Simplify complex queries
You can hide joins, subqueries, aggregations, calculations, or complicated WHERE clauses. Users query a simple view name instead of writing long SQL repeatedly. -
Enhance security and data protection
Grant SELECT permission only on the view (not on the base tables).
You can show only specific columns or specific rows (row-level security).
Example: Show only salary information to HR users, hide it from others. -
Provide data abstraction / logical data independence
The underlying table structure can change (column names, split tables, etc.), but applications can continue using the same view name without code changes — as long as the view definition is updated accordingly. -
Present data in a user-friendly or business-oriented way
Rename columns to more meaningful names.
Combine data from multiple tables into one logical “business view”.
Format or derive new columns (e.g.,CONCAT(first_name, ' ', last_name) AS full_name). -
Improve consistency
Everyone uses the same definition for “sales this year”, “active customers”, “inventory status”, etc. → avoids different people writing slightly different (and possibly wrong) queries. -
Logical data organization without duplication
No extra storage is needed (except the view definition itself).
The data remains in the base tables — views just provide different “windows” into the same data. -
Support some updatable views (with restrictions)
Simple views (usually on one table, no joins, no aggregates, etc.) can allow INSERT, UPDATE, DELETE operations that pass through to the base table.
Summary Table: Key Advantages of Views
| Benefit | Description |
|---|---|
| Simplicity | Hide complexity of joins, filters, calculations |
| Security | Column-level and row-level access control |
| Data abstraction | Protect applications from underlying table changes |
| Consistency | Standardize common queries across users/applications |
| No storage overhead | Virtual — only definition is stored |
| Readability | More meaningful column names and structure for end users |
Views are one of the most powerful and commonly used features in DB2 (and relational databases in general) for building maintainable, secure, and user-friendly database applications.
References:
- DB2 Views - db2tutorial.com
- IBM Db2 Documentation - CREATE VIEW
- Tutorialspoint - DB2 Views
- Mainframe Tech Help - DB2 View