SkillCoded

SQL Fundamentals

Sort, Limit, and Remove Duplicates

Control result ordering, row limits, and duplicate removal without confusing presentation choices with stored data or complete pagination.

Beginner14 min read
SQL Fundamentals lessonRelational data foundationsPractice

UNTIMED COACHING

Practice before the pressure

Use feedback to correct the model, not merely memorize an option position.

GUIDED PRACTICE

Practice the lesson questions

Answer normal lesson questions without a timer. Every answer includes an explanation, and incorrect answers can be tried again before continuing.

CONCEPT MODELS

See the lesson as a system

Use these visual guides to connect the key ideas before answering the questions.

Connect the roles in Sort, Limit, and Remove DuplicatesKeep sort key, distinct values, row limit, and duplicate inspection as separate roles.
Connect the roles in Sort, Limit, and Remove DuplicatesA topic-specific model connects four distinct roles used to reason about sort, limit, and remove duplicates.
Sort decisionDecision orders rows by timestamp
Row resultResult removes repeated customer values
Limit valueData value caps returned row count
Output evidenceEvidence compares rows before duplicate removal
Verify Stable paginationConnect stable pagination with its topic-specific inspection, expected outcome, and protected database boundary.
Verify Stable paginationA verification model for sort, limit, and remove duplicates connects the final data decision to its check, result, and protected boundary.
Selection ruleDecision protects repeatable page boundaries
Starting checkReview selection rule
Expected resultConfirm selection rule
Safety boundaryProtect sort decision scope