# Class 21 — Cardinality Violation

> Members and evidence boundaries for PostgreSQL SQLSTATE class 21.
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# Class 21 — Cardinality Violation

## Shared meaning {#meaning}

The first two characters `21` identify `Cardinality Violation`. A result has the wrong cardinality for the operation. A class gives a directory-level family; each member still needs its own message, transaction aftermath, and response evidence.

## Members {#members}

The locked catalogue contains 1 members in this class:

[`21000`](../../21000/)

## Version boundary {#versions}

Member links lead to their own versioned facts; consult the version pages and source evidence for exact presence and change boundaries.

## Sources {#sources}

Members are generated from `data/classes.json` and the locked SQLSTATE directory.