Query Optimizer
Definition
A query optimizer selects a likely efficient execution plan.
A database component that selects a likely efficient query plan from possible execution paths.
Simply explained
The database considers in which order and by which method it can best find the requested data.
Why it matters in practice
The term improves reliable access to data and knowledge as well as their usable linkage in digital systems.
Example from business
The optimizer decides between index access, hash join, and sequential scan.
Limits and pitfalls
- Taking cost estimates as guaranteed or ignoring outdated statistics and parameter values.
Origin & history
Cost-based optimization was fundamentally established with relational database systems like System R.
Use in mid-sized companies
- Possible application: The optimizer decides between index access, hash join, and sequential scan.
Frequently asked questions
What does query optimizer mean?
A database component that selects a likely efficient query plan from possible execution paths. What mistakes should be avoided? Taking cost estimates as guaranteed or ignoring outdated statistics and parameter values.
Sources
Source checked on 10.10.2026. Editorial application examples are hypothetical; no evidence of real customer results.
Editorially reviewed on: