5 SQL Query Optimization Techniques Every Engineer Must Know
Optimize query speeds, configure database indexes, prevent scan anomalies, and analyze execution explain plan structures.
Writing working queries is only the first step. In high-traffic systems, database index performance dictates system latency. Interviewers look for clean habits like avoiding wildcard reads and using indexing fields correctly.
1. Avoid SELECT * in production
Wildcard reads force disk operations, bypassing coverage indexes and loading unused text data. Specify columns directly to reduce memory and execution bounds.
2. Understand Index Coverage
An index creates a balanced-tree structure on specified columns. Lookups using indexed columns in WHERE filters take O(log N) time, whereas non-indexed comparisons trigger full table scans running in O(N) time.
Quick Concept Quiz
Why is 'SELECT *' avoided in high-performance production environments?
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