Using Triggers to Automate Internal Processing in Unidata

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Using Triggers to Automate Internal Processing in
Unidata

• Jeff Butera - Hampshire College
• http//jeff.hampshire.edu

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Outline

• What is a trigger?
• What can triggers do?
• How do I setup a trigger?
• How do I use them in production?
• Questions?

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What is a trigger?

• Piece of executed code
• Triggered by certain events

• Unidata Specifics
• Code is a Unibasic subroutine or function
• Triggers can be invoked whenever a record is
• Updated (written)
• Deleted

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What can triggers do?

• Triggers are useful for automated processing
• ADDOPR, CHGOPR (?!)
• Virtual fields too slow?
• No problem make em computed with a trigger
• Stored computed columns
• Status and/or status date fields
• Notify (email?) when certain things happen...

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How do I setup a trigger?

• Create subroutine with 5 arguments
• EXECSTAT (0,1,2)
• DICT.FLAG (, DICT)
• FILE (STUDENTS)
• ID (0023450)
• RECORD
• Compile and GLOBALLY catalog
• CREATE.TRIGGER FILENAME SUBNAME UPDATE

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How do I use these for real?

• Hampshire has truckloads of custom code/files
• On ALL custom files, I use triggers for
• ADD/CHG OPER, DATE, TIME
• Why not Envision?
• We use triggers on some Datatel files too!
• We use WORKORDERS for Phys Plant and IT
• PPWP (Web Params) only allows single Plant Type
• and single email address for web work orders
• No problem worked around with a trigger

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• SUBROUTINE H08.UT.H08.CR.EVENTS(X.EXEC,X.DICT,X.FI
  LE,X.ID,X.REC)
• X.EXEC2
• IF X.DICT THEN
• X.REClt4gtUPCASE(_at_LOGNAME)
• X.REClt5gtDATE()
• X.REClt6gtTIME()
• IF X.REClt1gt THEN
• X.REClt1gtX.REClt4gt
• X.REClt2gtX.REClt5gt
• X.REClt3gtX.REClt6gt
• END
• END
• RETURN
• BASIC CUSTOM.SOURCE H08.UT.H08.CR.EVENTS
• CATALOG CUSTOM.SOURCE H08.UT.H08.CR.EVENTS FORCE
• CREATE.TRIGGER H08.CR.EVENTS H08.UT.H08.CR.EVENTS
  UPDATE

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Non-trivial examples

• Search for HTML tags in free-form text
• Strip bad (unprintable) ASCII from free-form text
• Correct WORKORDER plant/email
• Set billed flag for parking stickers
• Detect data irregularities with evaluations (text
  types)
• FMLA check for approved timecards
• Why not place this code in screens/batch
  processes?

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Where do I find more information?

• Unidata Documentation (thin)
• Developing Unibasic Applications
• Chapter 4 Maintaining Data in Files
• Database triggers pp. 4-6

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Questions?
Jeff Butera Hampshire College jbutera_at_hampshire.ed
u http//jeff.hampshire.edu