[AT] BREAK [(r)] [OF] operand1 [/n/]
|
statement
 |
END-BREAK |
[AT]
BREAK
[(r)] [OF]
operand1 [/n/]
|
||
|
|
statement |
|
DO
statement
DOEND |
||
This document covers the following topics:
For an explanation of the symbols used in the syntax diagram, see Syntax Symbols.
Related Statements: ACCEPT/REJECT |
AT START OF DATA | AT END OF DATA | BACKOUT TRANSACTION | BEFORE
BREAK PROCESSING | DELETE | END
TRANSACTION | FIND |
GET | GET SAME | GET TRANSACTION
DATA | HISTOGRAM
| LIMIT | PASSW | PERFORM BREAK
PROCESSING | READ |
RETRY | STORE | UPDATE
Belongs to Function Group: Database Access and Update
The AT BREAK statement is used to cause the execution of one or more
statements whenever a change in value of a control
field occurs. It is used in conjunction with automatic break processing and
is available with the following statements: FIND, READ,
HISTOGRAM, SORT, READ
WORK FILE.
The automatic break processing works as follows: Immediately after a record was read by
the processing loop, the control field is checked. If a value change is detected in
comparison to the previous record, the statements included in the AT BREAK
statement block are executed. This does not apply to the very first record in the
processing loop. In addition, when the processing loop is terminated (as reading of
records is complete or due to an ESCAPE
BOTTOM statement), a final execution of the statements in the
AT BREAK statement block is triggered.
For further information, see Automatic Break Processing in the Programming Guide.
An AT BREAK statement block is only executed if the object which contains
the statement is active at the time when the break condition occurs.
It is possible to initiate a new processing loop within an AT BREAK
condition. This loop must also be closed within the same AT BREAK
condition.
This statement is non-procedural (that is, its execution depends on an event, not on where in a program it is located).
Natural system
functions may be used in conjunction with an AT BREAK statement,
see Natural System Functions for Use in
Processing Loops in the System Functions
documentation and Example of System Functions with AT BREAK Statement in
the Programming Guide.
For further information, see also the section AT BREAK Statement in the Programming Guide. It covers topics such as:
Operand Definition Table:
| Operand | Possible Structure | Possible Formats | Referencing Permitted | Dynamic Definition | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
operand1 |
S | A | U | N | P | I | F | B | D | T | L | yes | no | |||||||
Syntax Element Description:
| Syntax Element | Description |
|---|---|
(r) |
Reference Notation: By default, the final
AT BREAK condition (for loop termination) is always related to the
outermost active processing loop initiated with a FIND, READ, READ WORK
FILE, HISTOGRAM or SORT statement.
With the notation
Example:
...
READ ...
FIND ...
FIND ...
AT BREAK ...
FIND ...
END-FIND
END-BREAK
END-FIND
END-FIND
END-READ
... In this example, the final AT BREAK condition is
related to the READ loop
initiated in line 0120. It would be possible to have it related to one of the
FIND loops initiated in line
0130 and 0140, but not to the one initiated in line 0160.
If
|
operand1
|
Control Field: The field used as the break
control field is usually a database field. If a user-defined variable is used, it
must be initialized prior to the evaluation of automatic break processing (see
BEFORE BREAK PROCESSING
statement). A specific occurrence of an array can also be used as a control field.
|
/n/ |
Notation /n/: The
notation /n/ may be used to indicate that
only the first n positions (counting from
left to right) of the control field are to be checked for a change in value. This
notation can only be used with operands of format A, B, N or P.
A control break occurs when the value of the
control field changes, or when all records in the processing loop for which the
|
statement ... |
Statement(s) to be Executed at Break Condition:
In structured mode, you must supply one or several suitable statements, depending on the situation. For an example of a statement, see Examples below. |
END-BREAK |
End of AT BREAK Statement:
In structured mode, the Natural reserved word In reporting mode, use the |
Multiple AT BREAK statements may be specified within a processing loop
within the same program module. If multiple BREAK statements are specified
for the same processing loop, they form a hierarchy of break levels independent of whether
they are specified consecutively or interspersed within other statements. The first
AT BREAK statement represents the lowest control break level, and each
additional AT BREAK statement represents the next higher control break
level.
Every processing loop in a loop hierarchy may have its own break hierarchy attached.
| Structured Mode: | Reporting Mode: |
|---|---|
FIND ...
AT BREAK
...
END-BREAK
AT BREAK
...
END-BREAK
AT BREAK
...
END-BREAK
END-FIND
...
|
FIND ...
AT BREAK
DO
...
DOEND
AT BREAK
DO
...
DOEND
...
|
A change in the value of a control field in a break level causes break processing to be activated for that break level and all lower break levels, regardless of the values of the control fields for the lower break levels.
For easier program maintenance, it is recommended to specify multiple breaks consecutively.
See also Example 3 below and the section Multiple Control Break Levels in the Programming Guide.
This section covers the following topics:
For further examples of AT BREAK, see Natural System Functions for Use in Processing Loops,
Examples ATBEX3 and ATBEX4.
** Example 'ATBEX1S': AT BREAK (structured mode)
************************************************************************
DEFINE DATA LOCAL
1 EMPLOY-VIEW VIEW OF EMPLOYEES
2 CITY
2 COUNTRY
2 NAME
END-DEFINE
*
LIMIT 10
READ EMPLOY-VIEW BY CITY
AT BREAK OF CITY
SKIP 1
END-BREAK
DISPLAY NOTITLE CITY (IS=ON) COUNTRY (IS=ON) NAME
END-READ
*
END
CITY COUNTRY NAME
-------------------- ------- --------------------
AIKEN USA SENKO
AIX EN OTHE F GODEFROY
AJACCIO CANALE
ALBERTSLUND DK PLOUG
ALBUQUERQUE USA HAMMOND
ROLLING
FREEMAN
LINCOLN
ALFRETON UK GOLDBERG
ALICANTE E GOMEZ
Equivalent reporting-mode example: ATBEX1R.
** Example 'ATBEX2': AT BREAK (with /n/ notation)
************************************************************************
DEFINE DATA LOCAL
1 EMPLOY-VIEW VIEW OF EMPLOYEES
2 DEPT
2 NAME
END-DEFINE
*
LIMIT 10
READ EMPLOY-VIEW BY DEPT STARTING FROM 'A'
AT BREAK OF DEPT /4/
SKIP 1
END-BREAK
DISPLAY NOTITLE DEPT NAME
END-READ
*
END
DEPARTMENT NAME
CODE
---------- --------------------
ADMA01 JENSEN
ADMA01 PETERSEN
ADMA01 MORTENSEN
ADMA01 MADSEN
ADMA01 BUHL
ADMA02 HERMANSEN
ADMA02 PLOUG
ADMA02 HANSEN
COMP01 HEURTEBISE
COMP01 TANCHOU
** Example 'ATBEX5S': AT BREAK (multiple break levels) (structured mode)
************************************************************************
DEFINE DATA LOCAL
1 EMPLOY-VIEW VIEW OF EMPLOYEES
2 CITY
2 DEPT
2 NAME
2 LEAVE-DUE
1 #LEAVE-DUE-L (N4)
END-DEFINE
*
LIMIT 5
FIND EMPLOY-VIEW WITH CITY = 'PHILADELPHIA' OR = 'PITTSBURGH'
SORTED BY CITY DEPT
MOVE LEAVE-DUE TO #LEAVE-DUE-L
DISPLAY CITY (IS=ON) DEPT (IS=ON) NAME #LEAVE-DUE-L
/*
AT BREAK OF DEPT
WRITE NOTITLE /
T*DEPT OLD(DEPT) T*#LEAVE-DUE-L SUM(#LEAVE-DUE-L) /
END-BREAK
AT BREAK OF CITY
WRITE NOTITLE
T*CITY OLD(CITY) T*#LEAVE-DUE-L SUM(#LEAVE-DUE-L) //
END-BREAK
END-FIND
*
END
CITY DEPARTMENT NAME #LEAVE-DUE-L
CODE
-------------------- ---------- -------------------- ------------
PHILADELPHIA MGMT30 WOLF-TERROINE 11
MACKARNESS 27
MGMT30 38
TECH10 BUSH 39
NETTLEFOLDS 24
TECH10 63
PHILADELPHIA 101
PITTSBURGH MGMT10 FLETCHER 34
MGMT10 34
PITTSBURGH 34
Equivalent reporting-mode example: ATBEX5R.