How can a specific record in a database table be uniquely identified?

To uniquely find a record in a database table, a primary key is usually used — a unique field or set of fields that unambiguously identify the record. For example, if the table has a field id with unique values, you can perform a query:

SELECT * FROM table_name WHERE id = 123;

If a primary key is absent, you can use unique indexes or a combination of fields that guarantee the record's uniqueness.