Move the filter, change the rows

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</style></head><body><main><header><p class="kicker">SQL SEMANTICS · TWO REVIEWED STATEMENTS</p><h1>Move the filter, change the rows</h1><p>Three students, three tasks, two reviewed queries. Logical model only: no database connection, optimizer plan, or arbitrary SQL parser.</p></header><div class="actions"><button type="button" id="a">A · Status in ON</button><button type="button" id="b">B · Status in WHERE</button><button type="button" id="inspect">Inspect supported query</button><button type="button" id="reset">Reset A</button></div><section class="panel"><h2>Query and source</h2><label for="sql">Reviewed SQL</label><textarea id="sql" rows="4">SELECT s.id AS student_id, t.id AS task_id FROM students AS s LEFT JOIN tasks AS t ON t.student_id = s.id AND t.status = 'done' ORDER BY s.id, t.id;</textarea><p>Students:1,2,3. Tasks:(11,1,done),(12,1,todo),(13,2,todo).</p></section><div class="two"><section class="panel"><h2>Logical clause map</h2><div id="map" class="result" role="status" aria-live="polite"></div></section><section class="panel"><h2>Computed expected rows</h2><div id="count" class="result" role="status" aria-live="polite"></div><div id="rows"></div></section></div><div id="status" class="result" role="status" aria-live="polite"></div><footer>These two logical models explain ON versus WHERE filtering; test your own SQL in its intended database.</footer><noscript>JavaScript is required for the local controls. The accompanying article contains worked examples.</noscript></main><script>
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