Functions

• aka stored procedures
   
• Avoid whenever possible - expense + looping troubles
   
• To use in an index, mark it immutable
   
• Stable (within a transaction) now()
   
• Volatile - default form, if it changes within a scan (or has side effects)
   
• Alternatives:
   
  • Application
     
  • Internal functions
     
  • SQL commands
     
  • Temporary tables
     
  • Move to outer (e.g. left join)

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