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Sequence 073 — T1 - NULL, DISTINCT, ORDER BY and LIMIT

Stage: Technology Gate A — Relational Foundation
Source: CDMP Master Execution Manual

When / purpose

Handle basic inspection patterns without confusing missing, unique and sorted results.

What you should learn

  • NULL is not the same as blank/zero.
  • IS NULL / IS NOT NULL.
  • DISTINCT.
  • ORDER BY and LIMIT.

What to read / study

Priority Resource Use now Stop point
MUST Technology Competency Roadmap Use the exact active technology block and stopping boundary. Do not study later blocks.
REFERENCE Detailed Technology Competency Reference Use only the section named by this card. Do not convert the reference into a separate curriculum.

Do this in order

  1. Find missing values in a practice table.
  2. Compare row counts with distinct-value counts conceptually.
  3. Sort and sample records.
  4. Explain why LIMIT does not make a query representative.

Meridian application

Use Meridian synthetic data and the local lab environment only when the card calls for practice.

Create / save

Inspection-query set.

Stop / boundary

Stop at governance/data-management working depth; do not expand into DBA or engineering specialization.

Completion gate

You can inspect missingness, distinct values and ordered samples correctly.

NEXT → Sequence 074 — T1 - CASE and simple expressions

Operationalized from the verified canonical 00C Master Execution Manual; not a verbatim transcription.

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