SQL WHERE: Define the Rows That Belong in a Report

The practice task

List completed assignments submitted on or after a stated date. The fictional fixture contains an older completion, a recent draft and a recent completion with no submission date.

The data below is fictional. Run the example in a new SQLite database. It was checked with SQLite 3.51.0; other databases may use different syntax, functions or type rules.

Complete worked query

Create the small fixture and run the query together. The IDs, boundary values and missing entries make the result small enough to check by hand.

CREATE TABLE assignments(id INTEGER, status TEXT, submitted TEXT);
INSERT INTO assignments VALUES (1,'completed','2026-09-01'),(2,'draft','2026-10-05'),(3,'completed','2026-10-06'),(4,'completed',NULL);

SELECT id, submitted FROM assignments
WHERE status = 'completed' AND submitted >= '2026-10-01'
ORDER BY id;

Checked result

This is the result of the exact example above. NULL marks a missing database value rather than the text string "NULL".

Read the result

Only assignment 3 satisfies both conditions. Assignment 1 is too old, assignment 2 is a draft and assignment 4 has no known date that establishes it is inside the reporting period. The query does not edit any assignment.

The dates here use a consistent ISO year-month-day text format. That assumption makes the lexical comparison useful for these values. Mixing date formats or adding timestamps with different offsets requires a normalization and time-boundary decision first.

A filtered report cannot distinguish absent records from records excluded by its conditions unless you inspect the source. When a count looks low, check one condition at a time and review the rejected examples. Do not remove a condition just to make a total match an expectation.

Mistakes to check

Use these checks when adapting the example to a different dataset.

• Keep the source population and the reporting period explicit.
• Do not write = NULL to find a missing value.
• Check boundary dates and incomplete records when verifying a filter.