Q.What is a primary key? How is a primary key set for a table in LibreOffice Base?

This question asks both for the meaning of a primary key and the practical steps to set one in Base.

A primary key is a field (or a combination of fields) whose value uniquely identifies each record in a table. No two records may have the same primary-key value, and it can never be left blank. For example, RollNo is a natural primary key for a Student table.

Setting a primary key in LibreOffice Base:

1. Open the table in Design View.
2. Click to select the field that should be the primary key (for example, RollNo).
3. Right-click the small grey button at the left of that field's row and choose Primary Key from the menu.
4. A small key symbol appears beside the field, showing it is now the primary key.
5. Save the table. …

A primary key must be both unique and non-blank — do not choose a field (like Name) that could repeat or be empty. Also, setting a primary key …