by Markus Winand.

Obfuscated Conditions

The following sections demonstrate some popular methods for obfuscating conditions. Obfuscated conditions are where clauses that are phrased in a way that prevents proper index usage. This section is a collection of anti-patterns every developer should know about and avoid.


  1. Dates — Pay special attention to DATE types

  2. Numeric Strings — Don't mix types

  3. Combining Columns — use redundant where clauses

  4. Smart Logic — The smartest way to make SQL slow

  5. Math — Databases don't solve equations

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Markus Winand teaches efficient SQL—inhouse and online. He minimizes the development time using modern SQL and optimizes the runtime with smart indexing. His book entitled SQL Performance Explained has become standard reading.

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