Q91. DROP vs TRUNCATE?
While both `DROP` and `TRUNCATE` are DDL operations, their scope is fundamentally different: | Feature | `TRUNCATE TABLE` | `DROP TABLE` | | :--- | :--- | :--- | | **Data...
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Q92. Add order_date column to order table?
To add an `order_date` column to an existing table, use `ALTER TABLE ... ADD COLUMN`: ```sql ALTER TABLE `orders` ADD COLUMN order_date DATE NOT NULL DEFAULT (CURRENT_DAT...
Q93. Rename column Address to Addr in Customer?
```sql -- MySQL ALTER TABLE Customer CHANGE Address Addr VARCHAR(50); -- PostgreSQL / Standard ALTER TABLE Customer RENAME COLUMN Address TO Addr; ```
Q94. Delete column CITY from ADDRESSES?
To remove a column from an existing table schema, use `ALTER TABLE ... DROP COLUMN`: ```sql ALTER TABLE addresses DROP COLUMN city; ``` *Production Warning:* Dropping a c...
Q95. What are Indexes?
Data structures (typically B-Trees) that speed up data retrieval at the cost of slower writes and extra storage. Think of them as a book's table of contents.
Q96. Clustered vs Non-Clustered?
- **Clustered**: Determines physical storage order. One per table. The data IS the index. - **Non-Clustered**: Separate structure with pointers to data. Multiple allowed ...
Q97. Statement for assigning privileges?
`GRANT`. To remove: `REVOKE`. ```sql GRANT SELECT, INSERT ON database.orders TO 'app_user'@'%'; REVOKE DELETE ON database.orders FROM 'app_user'@'%'; ```
Q98. Types of privileges?
1. **System privileges**: CREATE, DROP, ALTER (database-level) 2. **Object privileges**: SELECT, INSERT, UPDATE, DELETE, EXECUTE (table/procedure-level)
Q99. Privileges a user can grant?
In SQL security management, database administrators can grant specific privileges using the `GRANT` statement: - **Data Manipulation Privileges**: `SELECT`, `INSERT`, `UP...
Q100. What is SQL Injection?
A code injection attack where malicious SQL is inserted via user input. Prevention: 1. **Parameterized queries** (prepared statements) 2. **Input validation** 3. **ORM fr...