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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.
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