ADELIA |
VADELIA |
SADELIA |
WADELIA |
EADELIA |
(I/B) |
(I/B) (S) |
(B) (S) |
(I/B) (S) |
(B) (S) |
Section for use
All
Syntax
CHAIN ViewName Option Parameter
Option |
→ |
*UNLCK | None |
Parameter |
→ |
*NO_MR | *MR | None |
Description
This instruction corresponds to a file read by key or by record number. A view ViewName must have been previously defined as having access by key (or direct), and the access key must correspond to the file key.
It is possible to test whether the reading was successful by an instruction of the type:
IF ViewName EXISTS |
|
or |
IF ViewName DOES_NOT_EXIST. |
If the read operation is not completed successfully, the system will not read any records at all, and the values of the file fields will remain unchanged.
You can also check that the record is not locked, by testing it with the *LOCKED reserved word:
If *LOCKED = 1 |
The record is locked. |
If *LOCKED = 0 |
The record is not locked. |
By default, file records are locked after being read if the file's view ViewName is declared in update mode and the *UNLCK reserved word is not used.
See the UNLOCK instruction which enables a file record to be released.
IF *UNLCK is mentioned, the reading does not lock the record. This parameter, used on a file opened in update mode, enables the same effect as if it had been declared in read-only mode.
The *MR parameter allows you to generate read implicit management rules that are linked to the entity corresponding to the view, even if the program is generated without the option to generate implicit management rules.
The *NO_MR parameter allows you not to generate read implicit management rules that are linked to the entity corresponding to the view, even if the program is generated with the option to generate implicit management rules.
Example
Example for SALES file (file keys are: customer code and line number).
SALES view is used with W_CUST_CODE and W_LINE_NBR as access keys.
SALES_CUST_CODE |
SALES_LINE_NBR |
0002 |
01 |
0002 |
02 |
0002 |
03 |
0002 |
04 |
0006 |
01 |
0006 |
02 |
0011 |
01 |
W_CUST_CODE = '0006'
W_LINE_NBR = '01'
CHAIN SALES
IF SALES DOES_NOT_EXIST
PREPARE_MSG 0024 W_CUST_CODE
ERROR
END
* This will position the pointer in the file on customer 0006 / line 01
* The record exists, so message 0024 will NOT be sent
*
W_CUST_CODE = '0006'
W_LINE_NBR = '03'
CHAIN SALES
IF SALES DOES_NOT_EXIST
PREPARE_MSG 0024 W_CUST_CODE
ERROR
END
* The record does not exist, so message 0024 will be sent
*
Other example:
CHAIN ORDHEADER_DA
IF ORD_HEADER_DA EXISTS
* lock test
IF *LOCKED = '1'
PW_RET_COD = 'DN'
ELSE
PRESENT ORDHEADER_DA
CHAIN CUSTOMER_DB
...
END
END