Master 3 concatenation patterns (||, CONCAT, +) and when each breaks

Transform strings (UPPER, LOWER, TRIM, SUBSTRING) with real-world data cleaning

Search & extract (LIKE, POSITION, LENGTH) with pattern matching rules

Handle NULL correctly in string operations (no silent failures)

Identify why string functions in WHERE kill index performance (50s vs 2s)

Write cross-database compatible code (PostgreSQL ≠ MySQL ≠ SQL Server)

Master 3 concatenation patterns (||, CONCAT, +) and when each breaks

Transform strings (UPPER, LOWER, TRIM, SUBSTRING) with real-world data cleaning

Search & extract (LIKE, POSITION, LENGTH) with pattern matching rules

Handle NULL correctly in string operations (no silent failures)

Identify why string functions in WHERE kill index performance (50s vs 2s)

Write cross-database compatible code (PostgreSQL ≠ MySQL ≠ SQL Server)