Reject duplicate business identifiers.
SQL Server: A UNIQUE constraint protects a business key independently of the primary key.
CREATE TABLE accounts (id INTEGER PRIMARY KEY,email VARCHAR(80) NOT NULL UNIQUE);
INSERT INTO accounts VALUES (1,'ada@example.invalid');
SELECT email FROM accounts;Expected output EXAMPLE
ada@example.invalid
Details
Requires SQL Server 2022 or later. Run in an empty scratch database in SSMS or sqlcmd. Result rows below use | between columns, without headers; client display formatting may differ. A UNIQUE constraint protects a business key independently of the primary key. The CREATE and INSERT statements provide all input data. Run the complete example in a fresh scratch database or schema.
Tested on Ubuntu 24.04.5 LTS · · SQL Server 16.0.4295.3 · 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
eca496dadbc01b6a04e2de52942a5ebff5ea66535988278f374156b1ee8af4fa- 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.
# No input files required.
Observed standard output
ada@example.invalid
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 accounts VALUES (2,'ada@example.invalid');