Q111. Are views updatable?
**Some views are updatable, but under strict structural criteria**: ### Conditions for a View to Be Updatable: 1. Must reference **only one base table** in the `FROM` cla...
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Q112. Advantages of views?
1. **Simplify complex queries** — hide JOINs and aggregations 2. **Security** — expose only specific columns/rows 3. **Logical independence** — shield apps from schema ch...
Q113. Does a view contain data?
**Standard SQL views do NOT contain data**. - **Standard Views (Virtual)**: Contain only a stored SQL query definition in the data dictionary. Every query against the vie...
Q114. How to remove a view?
To delete a view from the database, use the **`DROP VIEW`** command: ```sql DROP VIEW IF EXISTS active_customer_summary; ``` Dropping a view removes only the stored query...
Q115. Can a view be based on another view?
**Yes**, a view can be defined on top of another existing view (known as a **nested view**): ```sql CREATE VIEW us_customers AS SELECT * FROM Customers WHERE country = 'U...
Q116. Iterate over rows in a stored procedure?
To iterate row-by-row over a query result set inside a stored procedure, use a **`CURSOR`**: ### Cursor Lifecycle Steps: 1. **`DECLARE`**: Define the cursor and query. 2....
Q117. Process of finding a good query execution strategy?
**Query optimization**. The database's query optimizer generates multiple execution plans and picks the cheapest one based on statistics, indexes, and cost models. You ca...
Q118. What is a trigger?
A stored procedure that automatically executes in response to a DML event (INSERT, UPDATE, DELETE) or DDL event (CREATE, ALTER, DROP). Components: **Event** (when), **Con...
Q119. A stored procedure auto-executing on INSERT/UPDATE/DELETE?
A specialized database procedure that automatically executes in response to data modification events (`INSERT`, `UPDATE`, or `DELETE`) on a specific table is called a **T...