Jeff Butera - Hampshire College http://jeff.hampshire.edu Using Triggers to Automate Internal Processing in Unidata
Outline What is a trigger? What can triggers do? How do I setup a trigger? How do I use them in production? Questions?
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
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...
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
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
SUBROUTINE H08.UT.H08.CR.EVENTS(X.EXEC,X.DICT,X.FILE,X.ID,X.REC) X.EXEC=2 IF X.DICT=’’ THEN X.REC<4>=UPCASE(@LOGNAME) X.REC<5>=DATE() X.REC<6>=TIME() IF X.REC<1>=’’ THEN X.REC<1>=X.REC<4> X.REC<2>=X.REC<5> X.REC<3>=X.REC<6> 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
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?
Where do I find more information? Unidata Documentation (thin): Developing Unibasic Applications Chapter 4 – Maintaining Data in Files Database triggers pp. 4-6
Questions? Jeff Butera Hampshire College email@example.com http://jeff.hampshire.edu