Reference a parent identified by two columns.
Postgres: A composite foreign key checks the complete referenced key rather than either column independently.
CREATE TABLE parents (group_id INTEGER,id INTEGER,PRIMARY KEY(group_id,id));
CREATE TABLE children (id INTEGER PRIMARY KEY,parent_group INTEGER NOT NULL,parent_id INTEGER NOT NULL,FOREIGN KEY(parent_group,parent_id) REFERENCES parents(group_id,id));
INSERT INTO parents VALUES (1,10),(2,20);
INSERT INTO children VALUES (100,1,10);
SELECT parent_group,parent_id FROM children;Expected output EXAMPLE
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Details
Requires PostgreSQL 18. Run in an empty scratch schema using psql or a SQL client. Result rows below use | between columns, without headers; client display formatting may differ. A composite foreign key checks the complete referenced key rather than either column independently. The CREATE and INSERT statements provide all input data. Run the complete example in a fresh scratch database or schema.
SQLite connections must enable PRAGMA foreign_keys = ON before starting a transaction; the verification connection does so. PostgreSQL and SQL Server enforce these declared foreign keys directly.
Tested on Ubuntu 24.04.5 LTS · · PostgreSQL 18.6 (Debian 18.6-1.pgdg13+2) · bash 5.2.21-2ubuntu4; coreutils 9.4-3ubuntu6.3; psycopg 3.2.10; pymssql 2.3.8
Test inputs, results and environment
The exact published code ran in a dedicated Linux test container with prepared inputs. Snippet process uid 65534 with a read-only root filesystem and temporary working files. Database services use a private internal Docker network without published ports. Fresh scratch schema/database for each case; test database administrator credentials are confined to these disposable services. Fixtures and output records are isolated from the application database. Testing covers this example and its stated checks, not every input, operating system, or runtime version. The Linux container shares its host's kernel; this is not a native Windows test.
- Architecture / host kernel
- x86_64 / 6.18.54.1-microsoft-standard-WSL2
- Snippet identity / locale
- uid=65534, gid=65534 (unprivileged process) / C.UTF-8
- Interpreter invocation
Execute the exact SQL in a fresh database/schema; serialize result rows with | separators- Container image ID
sha256:ec91410a8f6ec3e985830b5e3a0560306d36f8c1c5ccd91a6699abe707123fa3- Code SHA-256
4a180f459eacac93d6bd02a290ea2c096fdf1e29c8ada37a5729efa097b99895- Dependencies
- bash 5.2.21-2ubuntu4; coreutils 9.4-3ubuntu6.3; psycopg 3.2.10; pymssql 2.3.8
Test input setup
These are the prepared inputs used by the test harness. See Details above for the prerequisites and how to run this example.
SQLite connection: PRAGMA foreign_keys = ON before executing the published SQL.
Observed standard output
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Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.
Additional assertions that passed
Checks recorded by the test harness. Where Python assertions are shown, browser cases use Playwright and simulator cases may inspect pin transitions: result.stdout is captured output, work is the temporary directory, and Path is pathlib.Path. The harness also imports json and csv.
Every tested engine rejected this invalid write with an integrity/constraint error: INSERT INTO children VALUES (101,1,20);