PostgreSQL

Identity Columns and Sequences

Use PostgreSQL identity columns and sequences for generated keys while distinguishing default generation, explicit values, transaction behavior, and uniqueness constraints.

Intermediate14 min read
PostgreSQL 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 Identity Columns and SequencesKeep identity column, sequence object, default generation, and insert result as separate roles.
Connect the roles in Identity Columns and SequencesA topic-specific model connects four distinct roles used to reason about identity columns and sequences.
Identity valueData receives generated ticket identifiers
Sequence serviceService supplies increasing numeric values
Generation processProcess supplies omitted identity values
Verified resultResult stores generated and imported ticket keys
Verify Generated key checkConnect generated key check with its topic-specific inspection, expected outcome, and protected database boundary.
Verify Generated key checkA verification model for identity columns and sequences connects the final data decision to its check, result, and protected boundary.
Output evidenceEvidence compares table keys and sequence state
Starting checkReview output evidence
Expected resultConfirm output evidence
Safety boundaryProtect identity value scope