What is a primary key in SQL?Ans. A primary key is a vital component of a table that serves as a unique identifier for each row. It consists of one or more columns whose values must be unique and non-null. By enforcing data integrity, a primary key ensures that each row in the table can be uniquely identified, and duplicate entries are not allowed. A primary key column must meet the following requirements: It must contain a unique value for each row in the table. It cannot contain null values. It must have a unique name within the table. It can be composed of one or more columns. Primary keys are usually used as a reference for foreign keys in related tables, creating a relationship between them. When creating a table, a primary key can be defined using the PRIMARY KEY constraint after the column or columns that should form the primary key.

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Ashish Verma · Accepted Answer

What is a primary key in SQL?Ans. A primary key is a vital component of a table that serves as a unique identifier for each row. It consists of one or more columns whose values must be unique and non-null. By enforcing data integrity, a primary key ensures that each row in the table can be uniquely identified, and duplicate entries are not allowed. A primary key column must meet the following requirements: It must contain a unique value for each row in the table. It cannot contain null values. It must have a unique name within the table. It can be composed of one or more columns. Primary keys are usually used as a reference for foreign keys in related tables, creating a relationship between them. When creating a table, a primary key can be defined using the PRIMARY KEY constraint after the column or columns that should form the primary key.

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