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| Parameter | Description | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Variable | Assigned a key from a select list. Each time ReadNext...By executes, the next available key from the list is assigned to variable. | |||||||||||||||
| Cursorvar | Contains a cursor variable. Cursor variables are initialized with a Select...By statement. | |||||||||||||||
| Direction | Indicates the direction in which the keys are read (ascending or descending) and whether the select list is terminating or non-terminating. If the list is non-terminating, the value of Status() is set to 1 after the last key has been read. The parameter direction must be an integer between 0 and 3. You can use alpha codes in the ReadNext...By command for clarity. Possible values:
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| Alphabetic codes are literal. | ||||||||||||||||
| Then | The statement(s) following Then are executed if a row key is read successfully. | |||||||||||||||
| Else | The statement(s) following Else are executed if a key cannot be read from the cursor. This is the case, 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 detail about the nature of the error. The Else branch is not typically used in nonterminating ReadNext...By statements, since the list is never exhausted. However, a Then or Else is still required in order for ReadNext to compile properly. Because ReadNext...By loads @RECORD, @ID and @DICT when resolving a latent list, any program using these variables for its own purposes should save them to local variables before using ReadNext...By. |
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.
See also
ClearSelect, Select...By, Read
Example: Processing the CUSTOMERS table with a cursor.
| Code Block |
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declare function Set_FSError open "CUSTOMERS" To CUSTOMERS_TABLE else status = Set_FSError() return end /* Select...By initializes a Cursor with a sorted list of customer records. A ReadNext and Read loop reads each record in turn, passing the customer records to a local subroutine (not shown) for processing. Note the use of the Cursor keyword and the Cursorvar. */ CURSOR_NO = "" Select "CUSTOMERS" By "STATE" setting CURSOR_NO else status = Set_FSError() Return end Done = 0 loop ReadNext @ID using CURSOR_NO 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 |
Example Using a Terminating Cursor
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