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Software Engineering vocabulary · Databases and Persistence

Primary key

Meaning in software engineering, with examples

/ˈpraɪmɛri kiː/nounCore term

In software engineering, primary key means: A column, or a set of columns, whose value uniquely identifies each row in a table. It cannot be empty and no two rows can share it.

In Turkish: birincil anahtar, PK

How it is used

Every well-designed table has exactly one primary key, often an id column. People shorten it to PK in diagrams and chat. You define, add or change a primary key; a 'duplicate key' error means you tried to insert a value that already exists.

Example sentences

  1. The primary key of the orders table is order_id.

  2. The import failed with a primary key violation, so some IDs must already exist.

Common collocations

  • define a primary key
  • primary key column
  • primary key violation
  • composite primary key
  • foreign keyA column in one table that points to the primary key of another table, linking the two and stopping you from storing references to rows that do not exist.
  • unique constraintA rule that stops two rows from having the same value in a column or combination of columns, for example two users with the same email address.
  • composite keyA key made of two or more columns that identify a row only when used together, such as order ID plus product ID in an order items table.
  • surrogate keyAn artificial key with no business meaning, such as an auto-increment number or a UUID, created only to identify each row.
  • auto-incrementDescribes a numeric column whose value the database fills in automatically with the next number in sequence each time a new row is added.

This word in other fields

The same English word can have a different meaning in another field:

More terms: Databases and Persistence

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