Keep unmatched rows with LEFT JOIN.
Show every product even when stock is missing.
CREATE TABLE products (id INTEGER PRIMARY KEY, name VARCHAR(40), category VARCHAR(20), price INTEGER);
INSERT INTO products VALUES (1, 'Pen', 'office', 3), (2, 'Book', 'office', 12), (3, 'Mug', 'kitchen', 8);
CREATE TABLE stock (product_id INTEGER PRIMARY KEY, quantity INTEGER);
INSERT INTO stock VALUES (1, 10), (3, 4);
SELECT p.name, COALESCE(s.quantity, 0) FROM products p LEFT JOIN stock s ON s.product_id = p.id ORDER BY p.id;Expected output EXAMPLE
Pen|10 Book|0 Mug|4
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. A missing stock row supplies NULL, which this example displays as zero. 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
267aeb97ba409b9df8a32f865971aabacd3ae2569d3173e80c7edd84dd631fe2- 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
Pen|10 Book|0 Mug|4
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.