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Cursors and Retrieve Loops Compared
Use cursors:
When a program needs to scan a table to update or delete rows
When a program requires access to other tables (or cursors) while processing rows
When more than one table needs to be scanned simultaneously ("parallel query")
When more than one table needs to be scanned in a nested fashion, for example, in a master-detail application
Use retrieve loops if the program is scanning the rows to:
Generate a report, or
Accumulate general statistics
For straightforward reading operations, the retrieve loop runs faster than a cursor. However, you cannot execute other queries inside a retrieve loop.
The following example shows the use of a retrieve loop and a cursor to scan a table:
begin program
## ename           character_string(21)
## salary          float
## eno, thatsall  integer
## ingres "personnel"
## range of e is employee
## /* retrieve loop */
## retrieve (ename = e.empname, eno = e.empnum,
## salary = e.#salary)
## sort by #ename
## {
     print ename, eno, salary
## }
 
## /* cursor retrieve */
## declare cursor c1 for
##   retrieve (e.empname, e.empnum, e.#salary)
##   sort by empname
## open cursor c1
   loop until thatsall = 1
##    retrieve cursor c1 (ename, eno, salary)
##    inquire_ingres (thatsall = endquery)
      if thatsall = 0 then
    
    print ename, eno, salary
      end if
     end loop
## close cursor c1
## exit
end program
Last modified date: 08/28/2024