2.12- What Is Alternate Key & Composite Key In Dbms In Hindi - Alternate Key & Composite Key Hindi
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What are Keys in DBMS?
KEYS in DBMS is an attribute or set of attributes which helps you to identify a row(tuple) in a relation(table). They allow you to find the relation between two tables. Keys help you uniquely identify a row in a table by a combination of one or more columns in that table. Key is also helpful for finding unique record or row from the table. Database key is also helpful for finding unique record or row from the table.
What is the Alternate key?
ALTERNATE KEYS is a column or group of columns in a table that uniquely identify every row in that table. A table can have multiple choices for a primary key but only one can be set as the primary key. All the keys which are not primary key are called an Alternate Key.
Example:
In this table, StudID, Roll No, Email are qualified to become a primary key. But since StudID is the primary key, Roll No, Email becomes the alternative key.
StudID Roll No First Name LastName Email
1 11 Tom Price abc@gmail.com
2 12 Nick Wright xyz@gmail.com
3 13 Dana Natan mno@yahoo.com
What is the Composite key?
COMPOSITE KEY is a combination of two or more columns that uniquely identify rows in a table. The combination of columns guarantees uniqueness, though individually uniqueness is not guaranteed. Hence, they are combined to uniquely identify records in a table.
The difference between compound and the composite key is that any part of the compound key can be a foreign key, but the composite key may or maybe not a part of the foreign key.
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2.9- Keys And Types Of Keys- Super Key In ER Model In DBMS In Hindi | Super Key In DBMS [ Ссылка ]
2.10- Candidate Key In DBMS In Hindi | What Is Candidate Key In RDBMS in Hindi | GATE dbms lectures [ Ссылка ]
2.11- Primary Key In DBMS In Hindi | What Is Primary Key In RDBMS in Hindi | GATE dbms lectures [ Ссылка ] Notes Link:
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