Test missing values with IS NULL.
Find rows where an optional value is absent.
CREATE TABLE contacts (name VARCHAR(30), email VARCHAR(80));
INSERT INTO contacts VALUES ('Ada', NULL), ('Lin', 'lin@example.invalid');
SELECT name FROM contacts WHERE email IS NULL;Expected output EXAMPLE
Ada
Details
Run in a scratch SQL database. These portable examples are executed on both PostgreSQL and SQLite. Result rows below use | between columns, without headers; client display formatting may differ. Use IS NULL rather than = NULL, because NULL represents an unknown value. The CREATE and INSERT statements supply the complete example data; use a fresh database or remove those setup statements when adapting the query.
Tested on Ubuntu 24.04.5 LTS · · SQLite 3.45.1; PostgreSQL 18.6 (Debian 18.6-1.pgdg13+2) · sqlite3 3.45.1-1ubuntu2.8; 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
1190a009bc7b3f4e250faeb8e4cd6e6689a821590ca5399a146b2aeed17b36a3- Dependencies
- sqlite3 3.45.1-1ubuntu2.8; 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
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.