Creating Charts from Processed SQL Data

A chart is useful only when it makes a comparison or pattern easier to understand. JavaScript is a supporting technology; the assessed reasoning lies in the data choice, processing and justified output.

Prepare data in PHP

$labels = array_column($rows, "team_name");
$values = array_map("intval", array_column($rows, "points"));

Pass encoded data safely:

<script>
const labels = <?= json_encode($labels) ?>;
const values = <?= json_encode($values) ?>;
</script>

A chart library can use these arrays. Provide a visible title, axis labels, sufficient contrast and a text/table alternative.

Choose the chart

• bar chart: compare teams or categories
• line chart: change over ordered time
• avoid pie charts when many categories or close values impede comparison

Do not create a chart from raw unprocessed data when a grouped or calculated result is what users need.

Check

• Chart answers a stated question.
• SQL/PHP processing is explainable.
• Labels and units are present.
• Equivalent values are available without relying only on colour or graphics.
• Empty and extreme datasets are tested.