SkillCoded

SQL Fundamentals

Select Columns and Rows

Use SELECT and FROM to return intentional columns from a named table while distinguishing stored rows from the projected result.

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 Select Columns and RowsKeep select list, table source, row data, and query result as separate roles.
Connect the roles in Select Columns and RowsA topic-specific model connects four distinct roles used to reason about select columns and rows.
Selection decisionDecision chooses returned table columns
Table sourceTable supplies stored ticket rows
Row dataData preserves one ticket occurrence
Verified resultResult contains the requested fields
Verify Projection verificationConnect projection verification with its topic-specific inspection, expected outcome, and protected database boundary.
Verify Projection verificationA verification model for select columns and rows connects the final data decision to its check, result, and protected boundary.
Output evidenceEvidence confirms hidden fields stay absent
Starting checkReview output evidence
Expected resultConfirm output evidence
Safety boundaryDo not verify only the first visible value