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🗑️ Mastering the Uniface Erase Command: A Complete Guide

#uniface #database #programming #development

Working with Uniface can be challenging, especially when dealing with data deletion operations. Today, I'm diving deep into the erase command in Uniface 10.4 - one of the most powerful yet potentially dangerous operations you can perform! 💣

Note: This post is based on the official Uniface Documentation 10.4, and I had some assistance from AI to organize this comprehensive guide.

🎯 What is the Erase Command?

The erase statement in Uniface activates delete or deleteUp triggers for all occurrences in a component. Think of it as the nuclear option for data deletion - it's powerful, but you need to handle it with care! ⚠️

📝 Basic Syntax 

erase{/e {Entity}}
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🛠️ Key Features & Qualifiers

The /e Qualifier

The /e qualifier is your friend when you need to target specific entities:

  • ✅ Erases all occurrences of the specified Entity
  • 🔗 Includes inner entities if Cascading Delete relationship exists
  • 🎯 Provides more granular control over what gets deleted

📊 Return Values You Need to Know

Understanding return values is crucial for error handling! Here are the most important ones:

Value Meaning Action Required
0 ✅ Success Data successfully erased
1 🚫 Not allowed Check component activation mode
-2 📭 Empty table No data to erase
-6 💾 I/O error Check disk space, permissions, constraints
-11 🔒 Already locked Wait or handle concurrency

🔗 Relationship Handling

The erase command behaves differently based on your entity relationships:

🌊 Cascading Delete

Related entities get deleted automatically - like a domino effect! 🎯

🚫 Nullify Delete

Foreign keys in related entities become null - safer but requires cleanup 🧹

⛔ Restricted Delete

Erase fails if related entities exist - your safety net! 🛡️

💡 Pro Tips for Safe Usage

1. Always Ask for Confirmation 

trigger erase ; of component

if ($totocc(CUSTOMER) >= 1)
 askmess "%%$totocc(CUSTOMER) occurrences. Erase them all?"
 if ($status = 0)
 return
 endif
endif

erase
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2. Handle Errors Gracefully 

if ($status < 0)
 message "Erase error; see message frame"
 rollback
else
 if ($status = 1)
 message "Erase is not allowed"
 else
 message "Erase was successful"
 commit
 endif
endif
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3. For Complete Database Deletion

Need to delete everything? Use this pattern:

setocc "*",-1  ; Retrieve all occurrences
erase          ; Then erase them
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⚠️ Critical Warning

The erase command only deletes fetched occurrences! If you haven't retrieved data into your component, it won't be deleted. This is both a safety feature and a potential gotcha! 🎭

🚀 Best Practices

  • 🔍 Always validate data before erasing
  • 💾 Use transactions (commit/rollback)
  • 📝 Log important deletions
  • 🧪 Test thoroughly in development
  • 👥 Consider user permissions and roles
  • 📊 Monitor performance with large datasets

🎬 Conclusion

The Uniface erase command is incredibly powerful for bulk data operations, but with great power comes great responsibility! 🕷️ Always implement proper safeguards, error handling, and user confirmations.

Remember: it's much easier to prevent accidental data loss than to recover from it! 💪

Happy coding, and may your erases be intentional! 🎯✨

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