Table Scripting

This sample shows you how to check if the field has been changed from one value to another

 function UpdateRecord()
 {
   if (Values("case_AssignedUserId")+""=="undefined")
     return;  //bad update from crm..or field not changed
   var CaseRec=CRM.CreateQueryObj("SELECT * FROM Cases WITH (NOLOCK) WHERE " + WhereClause);
   CaseRec.SelectSQL();
   if (CaseRec("case_assigneduserid")!=Values("Case_AssignedUserId"))
   {
     ErrorStr="field value has changed from "+CaseRec("case_assigneduserid") +" to "+Values("Case_AssignedUserId");
   }
 }

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Altering CRM dates in Table level scripts

 var mydate = new Date();
 mydate.setDate(mydate.getDate() +7);
 Values("comp_customerstartdate") = mydate.getVarDate();

Ref: https://community.sagecrm.com/partner_community/b/hints_tips_and_tricks/archive/2011/03/07/setting-or-updating-date-fields-using-a-table-level-script.aspx

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Comparing previous values (in cases where you might want to run some code only when a field value has changed)

Within the UpdateRecord method stub you would first query the current record using

 var crec=CRM.FindRecord("agreement",WhereClause);

You would then compare values as in

 if (crec("comp_name")!=Values("comp_name"))...

For date fields you have to create a Date object

 var c_comp_renewaldate = new Date(crec("comp_renewaldate"));
 var v_comp_renewaldate = new Date(Values("comp_renewaldate"));

and then call the getDate() method of the Date object to do the comparison. You cannot compare the date objects as it will never match

 if (c_comp_renewaldate.getDate() != v_comp_renewaldate.getDate())...

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Useful learning tool if your trying to work out when each of the TLS functions are called.

Table level script will log all events to the SQL logs

 function log(message, error) {try{CRM.CreateQueryObj('/* '+((error)?message:message+' */')).SelectSql();}catch(e){}}

 function InsertRecord() { log("InsertRecord called",1); }

 function PostInsertRecord() { log("PostInsertRecord called",1); }

 function UpdateRecord() { log("UpdateRecord called.  WHERECLAUSE=" + WHERECLAUSE,1); }

 function DeleteRecord() { log("DeleteRecord called.  WHERECLAUSE=" + WHERECLAUSE,1); }

Ref: https://community.sagecrm.com/partner_community/b/hints_tips_and_tricks/archive/2011/08/19/how-do-you-know-if-your-table-level-scripts-are-being-executed.aspx