7 KEYS OF DBMS

For defining different kinds of integrity constraints in a database, we use a key. The records of different events for any relation are compiled in a table, on the other hand. These records could number in the thousands, and some of them might even be identical.

We therefore require a method of uniquely and separately identifying each of these records, i.e., without any duplications. The use of keys eliminates this inconvenience.

Consider a database of every student attending a college as an illustration. What quality about each student, in your opinion, will make them all uniquely identifiable? These students can be referred to using their names, departments, sections, and years. Similar to this, we can also provide just the university roll number and have that number be the basis for retrieving all the other information.

The keys in DBMSs can be a single attribute or a combination of several attributes (or columns). The main goal of the keys is to give each record its own distinct identity.

What are the 7 different types of keys in DBMS

• Primary Key
• Foreign Key
• Super Key
• Unique Key
• Composite Key
• Alternative Key
• Candidate Key

01. PRIMARY KEY

The term “primary key” describes a column or set of columns in a table that enable us to uniquely identify each record that is present in that table. One primary key can be present in a table. Additionally, no row of this primary key’s data can contain the same values repeatedly. A primary key must have unique values throughout, with no duplicates allowed.

The PK (PRIMARY KEY) constraint we apply to a column or set of columns prevents them from having a null value or a duplicate value. Only one primary key constraint is allowed for any table. Its values cannot ever be altered by a foreign key that refers to it (see the explanation below).

02. FOREIGN KEY

To create connections between two available tables, we use a foreign key. Every value in a column or set of columns must match the primary key in the referential table in order for the foreign key to function. We can maintain referential integrity and data integrity with the aid of a foreign key.

03. SUPER KEY

A super key is the collection of all the keys that enable us to uniquely identify each row in a table. It implies that all of the columns in a table that are able to uniquely identify the columns in that table serve as the super keys.

The superset of a candidate key, which has been described below, is a super key. To make a table’s primary key the attribute that identifies the table, we must choose it from the set of super keys.

04. UNIQUE KEY

A column or set of columns known as a unique key uniquely identifies each record in a table. This key would have to contain only unique values. Always keep in mind that a unique key differs from a primary key. This is so because there can only be one null value in it. On the other hand, a primary key cannot have a null value.

05. COMPOSITE KEY

The term “composite key” refers to a collection of various characteristics that enable us to identify each tuple in a table in a particular way. If we look at the attributes in a set separately, they might not all be unique. Thus, when we combine them all, it will guarantee complete uniqueness.

06. ALTERNATIVE KEY

Any table can have multiple options for the primary key, as we already mentioned. It can only select one, though. As a result, all keys that were not used as primary keys are referred to as alternate keys.

07. CANDIDATE KEY

The attributes that distinguish rows in a table one from another are referred to as candidate keys. From a candidate key in a table, we choose the primary key. Therefore, a candidate key shares many of the same characteristics as the primary keys we discussed above. There may be more than one potential key in a table.

CONCLUSION

When designing a database, keys and functional dependencies are crucial components. The distinction between good and poor database design can also be made using these ideas. The final step in eliminating redundancies and improving database performance is normalization, which makes use of all the ideas discussed in this article.

The most crucial aspect of keys is how they establish integrity and reveal the connection between two tables, enabling users to precisely edit data while maintaining uniqueness. The objective is to distinguish the identity of each record through distinctive keys defining distinct qualities, ranging from alternate keys to composite.