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Software Engineering vocabulary · Databases and Persistence

Composite key

Meaning in software engineering, with examples

/kəmˈpɑːzɪt kiː/nounCommon term

In software engineering, composite key means: A 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.

In Turkish: bileşik anahtar

How it is used

Typical in junction tables for many-to-many relationships. Some teams prefer a simple surrogate id plus a unique constraint on the column pair, because composite keys make foreign keys and ORM mappings longer. Also called a compound or multi-column key.

Example sentences

  1. The enrollments table uses a composite key of student_id and course_id.

  2. Column order matters in a composite key because of the index behind it.

Common collocations

  • composite primary key
  • composite key of
  • composite index
  • multi-column key
  • primary keyA 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.
  • many-to-many relationshipA link where many rows in one table can relate to many rows in another, like students and courses. It needs a third table in between to store the pairs.
  • surrogate keyAn artificial key with no business meaning, such as an auto-increment number or a UUID, created only to identify each row.
  • indexThe position number of an item in an array or list. In most languages counting starts at zero, so the first item has index 0.

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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