lesson
A view should not destroy source records
1 · Learn
Filtering shows records meeting conditions; sorting reorders them. Neither operation needs to delete the non-matching records. Preserve raw data and document cleaning changes so errors can be investigated.
For a query using AND, both conditions must hold; OR includes either. Missing values require a stated treatment rather than an unannounced replacement with zero or a guessed category.
2 · Worked example
In an invented table, A is nature/80 pages, B nature/30 and C history/90. Nature AND more than 50 pages returns A; the OR version returns all three.
3 · Your turn
Which of the stated records satisfies history AND more than 50 pages?
Check your answer
C only.
4 · Apply your learning
Predict query results before running them and compare the selected record IDs rather than only the total count.
Adult guidance and safety
Use an approved private interpreter, simulator or authoring tool with fictional data. Trace and predict before running. Never execute unknown downloaded code, inspect real credentials or use other people's private data. Working examples still need saved-project and assessment integration before release.
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Check a calculation · Year 5 onward
Use this only when your teacher or adult allows a calculator for the task. Show your thinking first. It does not replace mental or written arithmetic and does not mark your lesson answer.
Powers, roots and trigonometry · Year 7 onward
Use only when the task allows a calculator. Choose one operation at a time and record your working. Trigonometry here always uses degrees (DEG), not radians. Inverse sine, cosine and tangent return an angle, not a reciprocal. Keep exact fractions and π in answers when requested.
Approximate numerical results use up to 12 significant digits. Inverse sine returns −90° to 90°, inverse cosine 0° to 180°, and inverse tangent −90° to 90°; these are principal values, not every possible solution of a trigonometric equation.
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