Which key does hold uniqueness property?
Correct answer: A. All of these
- A. All of these
- B. Foreign key
- C. Primary key
- D. Alternate key
Explanation
• Foreign Key: A foreign key is a column or set of columns in one table that references the primary key of another table. It helps establish relationships between tables. Foreign keys also enforce referential integrity, which helps prevent data inconsistencies. By design, foreign keys reference existing data, so they are not unique within their own table.• Primary Key: A primary key is a special type of candidate key that is chosen to uniquely identify rows in a table. It follows the following properties:o Uniqueness: No two rows in the table can have the same value for the primary key.o Minimality: The primary key should not include any unnecessary columns.• Alternate Key : An alternate key is another candidate key that is not chosen as the primary key. It can also uniquely identify rows in the table
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Databases cover tables, records, fields, keys and relationships, together with database management systems and relational database design. The subject includes primary and foreign keys, normalization, SQL commands such as SELECT, INSERT, UPDATE and DELETE, queries, forms and reports, while distinguishing a database from a spreadsheet used for simple tabular data.
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