[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:
| (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/ | 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 |
| END-BREAK | The Natural reserved word END-BREAK
must be used to end the AT BREAK statement.
|
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.