I. EQUEL/FORMS Examples : Unloadtable
 
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Unloadtable
Loops through a table field data set, copying values to host variables and, optionally, executing a block of code once for each row.
Examples--unloadtable statement:
Example 1:
This example processes the records in the data set within a database multi-statement transaction:
## begin transaction
## range of e is employee
## unloadtable empform employee
##        (vname = ename, vage = age, vnum = eno,
##         state = _state)
## {
     /* undefined and unchanged are left alone */
     /* new is appended */
     if (state = 0) or 
        (state = 2) then 
         do nothing
     else if (state = 1) then 
##       append employee (empnum = vnum, empname = vname, 
##                        age = vage)
     /* reflect changed data */
     else if (state = 3) then
##        replace e (empname = vname, age = vage)
##        where e.empnum = vnum
     /* deleted row */ 
     else if (state = 4) then
##        delete e where e.empnum = vnum
## }
## end transaction
## clear field employee
Example 2:
The following example adds the integer values of number and puts the average in a field called avgvalue:
rows = 0
sumvals = 0
## unloadtable statistics accumulator
##  (vname = name, vnumber = number, record = _record)
## {
    if (vname = "") then
##       message "empty numeric identifier"
##       sleep 2
##       scroll statistics accumulator to record
##       resume field accumulator /* break out of loop */
    end if
    rows = rows + 1
    sumvals = sumvals + vnumber
## }
    if (rows > 0) then
         sumvals = sumvals/rows
    end if
## putform statistics (avgvalue = sumval)
Example 3:
This example finds the first employee over the age of 60:
 found = false
## unloadtable empform employee
##   (vname = ename, vage = age, state = _state,
##    record = _record)
## {
     if (vage > 60) and (state < 4) then /* not deleted */
          found = true
##        endloop
     end if
## }
     if (found) then
          process the specified record
     end if
Example 4:
This example illustrates the use of null indicator variables with nullable columns:
## activate menuitem "printroster"
## {
##   unloadtable empform employee
##         (vname = ename, vage = age
##         vspouse:indicator_var = spouse)
##   {
           /* do processing to create roster entry. */
##   }
## }
Example 5:
This example checks the change variable of rows in a table field data set:
## activate menuitem "printorders"
## {
##   unloadtable salesform saleslist
##         (vorder = order, vitem = item)
##   {
           /* check if item ordered has changed. */
##         inquire_frs row salesform saleslist
##              (changed = change(item))
           if (changed = 1) then
                 update the database
           end if
           process order and print out data
##   }
## }