Description
Extracts the next key from the list of keys, until the list is exhausted.
Syntax
ReadNext variable [ , value] [USING cursorvar] Then | Else statements
The ReadNext statement has the following fcparameters.
| Parameter | Description |
|---|---|
| variable | Is assigned the row key from the selected list. |
| value | When a multi-valued sort list is being used, you can use the optional variable value. It returns the position of variable in the multi-valued field. |
| cursorvar | A variable containing the cursor variable set for this table in a Select...By statement. |
| Then | Executed if the ReadNext is successful. |
| Else | The statement(s) following Else are executed if a key cannot be read from the selected list, for example, when the list has been exhausted. The Status() function indicates the reason for the false branch, and the system variable @FILE_ERROR contains details about the nature of the error. |
Note: A ReadNext may return a null record key before the active list is exhausted. Testing for the null key is not a reliable test for list exhaustion.
Use ReadNext to read the keys from a selected list. The list of keys can be from a BASIC+ Select statement. A Select statement is used in the BASIC+ program to create a list of record keys. For more information, refer to Read.
Caution: If you exit a ReadNext loop before exhausting the select list, you must clear the select list using ClearSelect. Otherwise, your results may be unpredictable.
Example: Processing the CUSTOMERS table.
declare function Set_FSError open "CUSTOMERS" To customers_table else status = Set_FSError() return end select customers_table Done = 0 loop ReadNext @ID else Done = 1 Until Done Do read @RECORD From customers_table, @ID else status = Set_FSError() return end * processing logic here ... GoSub PROCESS Repeat return 0 PROCESS: /* process the row */ return return
