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Question
Write a short note on Primary key constraints.
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Solution
Primary Constraint:
- Primly Constraint declares a field as a Primary key which helps to uniquely identify a recor<}ll
- Primary Constraint is similar to a unique constraint except that only one field of a table can be set as the primary key.
- The primary key does not allow NULL values and therefore a field declared as the primary key must have the NOT NULL constraint.
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| C1004 | Manjima | Clerk | 8000 | 4500 |
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| 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 |
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| 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 |
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