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प्रश्न
What is a constraint?
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उत्तर
Constraint:
- The constraint is a condition applicable on a field or set of fields.
- Constraints are used to limit the type of data that can go into a table.
- This ensures the accuracy and reliability of the data in the database.
- Constraints could be either on a column level or a table level.
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संबंधित प्रश्न
Write a query that selects all students whose age is less than 18 in order wise.
Differentiate Unique and Primary Key constraint.
Write the difference between table constraint and column constraint?
Which component of SQL lets inserts values in tables and which lets to create a table?
Write a short note on Primary key constraints.
Write a SQL statement using the DISTINCT keyword.
Consider the following employee table. Write SQL commands for the question.
| EMP CODE | NAME | DESIG | PAY | ALLO WANCE |
| S1001 | Hariharan | Supervisor | 29000 | 12000 |
| P1002 | Shaji | Operator | 10000 | 5500 |
| P1003 | Prasad | Operator | 12000 | 6500 |
| C1004 | Manjima | Clerk | 8000 | 4500 |
| M1005 | Ratheesh | Mechanic | 20000 | 7000 |
To display the details of all employees in descending order of pay.
Consider the following employee table. Write SQL commands for the question.
| EMP CODE | NAME | DESIG | PAY | ALLO WANCE |
| S1001 | Hariharan | Supervisor | 29000 | 12000 |
| P1002 | Shaji | Operator | 10000 | 5500 |
| P1003 | Prasad | Operator | 12000 | 6500 |
| C1004 | Manjima | Clerk | 8000 | 4500 |
| M1005 | Ratheesh | Mechanic | 20000 | 7000 |
To display all employees whose allowance is between 5000 and 7000.
What are the components of SQL? Write the commands in each.
Construct the following SQL statement in the student table-
SELECT statement using ORDER BY clause.
