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Using the sqlca
Every ALLBASE/SQL program must have the SQL Communications Area (sqlca)
declared in the global declaration part. You can use the INCLUDE command
to declare the sqlca:
EXEC SQL INCLUDE SQLCA;
When the C preprocessor parses this command, it inserts the following
type definition into the modified source file:
sqlca_type sqlca;
Optionally, you can use this type definition in the global declaration
part of your source file instead of using the INCLUDE command to declare
the sqlca.
The C preprocessor generates the following record declaration for
sqlca_type in the type declaration include file:
typedef struct {
char sqlaid[8];
int sqlabc;
int sqlcode;
int sqlerrl;
char sqlerrm[256];
char sqlerrp[8];
int sqlerrd[6];
char sqlwarn[8];
char sqlext[8];
} sqlca_type;
The following elements in this record are available for you to use in
status checking and are accessed as follows. The other elements are
reserved for use by ALLBASE/SQL only.
sqlcode or sqlca.sqlcode
sqlca.sqlerrd[2]
sqlca.sqlwarn[0] or sqlca.sqlwarn0
sqlca.sqlwarn[1] or sqlca.sqlwarn1
sqlca.sqlwarn[2] or sqlca.sqlwarn2
sqlca.sqlwarn[3] or sqlca.sqlwarn3 (used only for dynamic commands)
sqlca.sqlwarn[6] or sqlca.sqlwarn6
NOTE In conformance with the ANSI standard, either sqlcode or
sqlca.sqlcode may be used to address this particular element. And
each sqlwarn element can be addressed in two different ways.
The following table gives an overview of how ALLBASE/SQL sets these
fields. Each field is then described with brief examples of how you can
use it, including examples for using SQLEXPLAIN. Methods of handling
specific status checking tasks are found in the succeeding section,
"Approaches to Status Checking."
Table 4-1. sqlca Status Checking Fields
----------------------------------------------------------------------------------------
| | | |
| FIELD NAME | SET TO | CONDITION |
| | | |
----------------------------------------------------------------------------------------
| | | |
| sqlca.sqlcode or sqlcode | 0 | no error occurred during |
| | | command execution |
| | less than 0 | |
| | | error, command not executed |
| | 100 | |
| | | no rows qualify for DML |
| | | operation (does not apply to |
| | | dynamic commands) |
| | | |
----------------------------------------------------------------------------------------
| | | |
| sqlca.sqlerrd[2] | number of rows put | data retrieval operation |
| | into output host | |
| | variables | data change operation |
| | | |
| | number of rows | error in single row data |
| | processed | change operation |
| | | |
| | 0 | sqlcode equals 100 |
| | | |
| | 0 | |
| | | |
----------------------------------------------------------------------------------------
| | | |
| sqlca.sqlwarn[0] or | W | warning, command not properly |
| sqlca.sqlwarn0 | | executed |
| | | |
----------------------------------------------------------------------------------------
| | | |
| sqlca.sqlwarn[1] or | W | at least one character string |
| sqlca.sqlwarn1 | | value was truncated when being |
| | | stored in a host variable |
| | | |
----------------------------------------------------------------------------------------
| | | |
| sqlca.sqlwarn[2] or | W | at least one null value was |
| sqlca.sqlwarn2 | | eliminated from the argument |
| | | set of an aggregrate function |
| | | |
----------------------------------------------------------------------------------------
| | | |
| sqlca.sqlwarn[3] or | W | for dynamic commands only, |
| sqlca.sqlwarn3 | | when the number of host |
| | | variables in a SELECT or FETCH |
| | | is unequal to the number of |
| | | columns in the table being |
| | | operated on |
| | | |
----------------------------------------------------------------------------------------
| | | |
| sqlca.sqlwarn[6] or | W | the current transaction was |
| sqlca.sqlwarn6 | | rolled back |
| | | |
----------------------------------------------------------------------------------------
sqlcode
sqlcode can contain one of the following values:
* 0, when an SQL command executes without generating an error
condition and without generating a no rows qualify condition.
* A negative number, when an error condition exists and an
ALLBASE/SQL command cannot be executed.
* 100, when no rows qualify for one of the following commands, but
no error condition exists:
SELECT
INSERT
UPDATE (non-dynamic execution only)
DELETE (non-dynamic execution only)
BULK SELECT
FETCH
BULK FETCH
UPDATE WHERE CURRENT
DELETE WHERE CURRENT
Note that the absolute value of sqlcode is the same as the absolute value
associated with its corresponding message in the ALLBASE/SQL message
catalog. This absolute value is part of the returned message. If an
error occurs, the message number is preceded by DBERR. For example, the
error message associated with an sqlcode of -2613 is:
Precision digits lost in decimal operation MULTIPLY. (DBERR 2613)
Sqlcode is set by all SQL commands except the following directives:
BEGIN DECLARE SECTION
DECLARE
END DECLARE SECTION
INCLUDE
WHENEVER
When sqlcode is -4008, -14024, or a greater negative value than -14024,
ALLBASE/SQL automatically rolls back the current transaction. When this
condition occurs, ALLBASE/SQL also sets sqlwarn[6] to W. Refer to the
discussion later in this chapter on sqlwarn[6] for more on this topic.
More than one sqlcode is returned when more than one error occurs. For
example, if you attempt to execute the following SQL command, two
negative sqlcode values result:
EXEC SQL ADD PUBLIC, GROUP1 TO GROUP GROUP1;
The sqlcodes associated with the two errors are:
-2308, which indicates the reserved name PUBLIC is invalid.
-2318, which indicates you cannot add a group to itself.
To obtain all sqlcodes associated with the execution of an SQL command,
you execute the SQLEXPLAIN command until sqlcode is 0:
if (sqlca.sqlcode == 100) {
printf("No rows qualified for this operation.\n");
}
else
if (sqlca.sqlcode < 0) SQLStatusCheck();
.
.
.
int SQLStatusCheck()
{
do {
EXEC SQL SQLEXPLAIN :SQLMessage;
printf("%s\n",SQLMessage);
} while (sqlca.sqlcode != 0);
}
The function named SQLStatusCheck is executed when sqlcode is a negative
number. Before executing SQLEXPLAIN for the first time, the program has
access to the first sqlcode returned. Each time SQLEXPLAIN is executed
subsequently, the next sqlcode becomes available to the program, and so
on until sqlcode equals 0.
This example explicitly tests the value of sqlcode twice: first to
determine whether it is equal to 100, then to determine whether it is
less than 0. If the value 100 exists, no error will have occurred and
the program will display the message No rows qualify for this operation.
It is necessary for the program to display its own message in this case,
because SQLEXPLAIN messages are available to your program only when
sqlcode contains a negative number and when sqlwarn[0] contains a W.
The sqlcode is also used in implicit status checking:
* ALLBASE/SQL tests for the condition sqlcode less than 0 when you
use the SQLERROR option of the WHENEVER command.
* ALLBASE/SQL tests for the condition sqlcode equal to 100 when you
use the NOT FOUND option of the WHENEVER command.
In the following situation, when ALLBASE/SQL detects a negative sqlcode,
the code routine at label a2000 is executed. When ALLBASE/SQL detects an
sqlcode of 100, the code routine at label a4000 is executed instead:
EXEC SQL WHENEVER SQLERROR GOTO a2000;
EXEC SQL WHENEVER NOT FOUND GOTO a4000;
WHENEVER commands remain in effect for all SQL commands that appear
physically after them in the source program until another WHENEVER
command for the same condition appears.
The scope of WHENEVER commands is fully explained later in this chapter
under "Implicit Error Handling Techniques."
sqlerrd[2]
sqlca.sqlerrd[2] can contain one of the following values:
* 0, when sqlcode is 100 or when one of the following commands
causes an error condition:
INSERT
UPDATE
DELETE
UPDATE WHERE CURRENT
DELETE WHERE CURRENT
If an error occurs during execution of INSERT, UPDATE, or DELETE,
one or more rows may have been processed prior to the error. In
these cases, you may want to either COMMIT WORK or ROLLBACK WORK,
depending on the transaction. For example, if all or no rows
should be updated for logical data consistency, use ROLLBACK WORK.
However, if logical data consistency is not an issue, COMMIT WORK
may minimize re-processing time.
* A positive number, when sqlcode is 0. In this case, the positive
number provides information about the number of rows processed in
the following data manipulation commands.
The number of rows inserted, updated, or deleted in one of the
following operations:
INSERT
UPDATE
DELETE
UPDATE WHERE CURRENT
DELETE WHERE CURRENT
The number of rows put into output host variables when one of the
following commands is executed:
SELECT
BULK SELECT
FETCH
BULK FETCH
* A positive number, when sqlcode is less than 0. In this case,
sqlerrd[2] indicates the number of rows that were successfully
retrieved or inserted prior to the error condition:
BULK SELECT
BULK FETCH
BULK INSERT
As in the case of INSERT, UPDATE, and DELETE, mentioned above, you
can use either a COMMIT WORK or ROLLBACK WORK command, as
appropriate.
sqlwarn[0]
A W in sqlwarn[0], in conjunction with a 0 in sqlcode, indicates that the
SQL command just executed caused a warning condition.
Warning conditions flag unusual but not necessarily important conditions.
For example, if a program attempts to submit an SQL command that grants
an already existing authority, a message such as the following would be
retrieved when SQLEXPLAIN is executed:
User PEG already has DBA authorization. (DBWARN 2006)
In the case of the following warning, the situation may or may not
indicate a problem:
A transaction in progress was aborted. (DBWARN 2010)
This warning occurs when a program submits a RELEASE command without
first terminating a transaction with a COMMIT WORK or ROLLBACK WORK. If
the transaction did not perform any UPDATE, INSERT, or DELETE operations,
this situation will not cause work to be lost. If the transaction did
perform UPDATE, INSERT, or DELETE operations, the database changes are
rolled back when the RELEASE command is processed.
You retrieve the appropriate warning message by using SQLEXPLAIN. Note
that you cannot explicitly test sqlwarn[0] the way you can test sqlcode,
since sqlwarn[0] always contains W when a warning occurs.
An error and a warning condition may exist at the same time. In this
event, sqlcode is set to a negative number, and sqlwarn[0] is set to W.
Messages describing all the warnings and errors can be displayed as
follows:
if (sqlca.sqlcode != 0) {
do {
DisplayMessage();
} while (sqlca.sqlcode != 0);
}
.
.
.
int DisplayMessage()
{
EXEC SQL SQLEXPLAIN :SQLMessage;
printf("%s\n",SQLMessage);
}
If multiple warnings but no errors result when ALLBASE/SQL processes a
command, sqlwarn[0] is set to W and remains set until the last warning
message has been retrieved by SQLEXPLAIN or another SQL command is
executed. In the following example, DisplayWarning is executed when this
condition exists:
if ((sqlca.sqlcode == 0) & (sqlca.sqlwarn[0] == 'W')) {
do {
DisplayWarning();
} while (sqlca.sqlwarn[0] == 'W');
}
.
.
.
int DisplayWarning()
{
EXEC SQL SQLEXPLAIN :SQLMessage;
printf("%s\n",SQLMessage);
}
When you use the SQLWARNING option of the WHENEVER command, ALLBASE/SQL
checks for a W in sqlwarn[0]. You can use the WHENEVER command to do
implicit status checking (equivalent to that done explicitly above) as
follows:
EXEC SQL WHENEVER SQLWARNING GOTO a3000;
EXEC SQL WHENEVER SQLERROR GOTO a2000;
sqlwarn[1]
A W in sqlwarn[1] indicates truncation of at least one character string
value when the string was stored in a host variable. Any associated
indicator variable is set to the value of the string length before
truncation.
For example:
EXEC SQL SELECT PartNumber,
PartName
INTO :PartNumber
:PartName :PartNameInd
FROM PurchDB.Parts
WHERE PartNumber = :PartNumber;
If PartName was declared as a character array of 20 bytes, and the
PartName column in the PurchDB.Parts table has a length of 30 bytes, then
the following occurs:
* sqlwarn[1] is set to W.
* PartNameInd is set to 30 (the length of PartName in the table).
* sqlcode is set to 0.
* SQLEXPLAIN retrieves the message:
Character string truncation during storage in host variable.
(DBWARN 2040)
sqlwarn[2]
A W in sqlwarn[2] indicates that at least one null value was eliminated
from the argument set of an aggregrate function.
For example:
EXEC SQL SELECT MAX(OrderQty)
INTO :MaxOrderQty
FROM PurchDB.OrderItems;
If any OrderQty values are null, the following occurs:
* sqlwarn[2] is set to W.
* sqlcode is set to 0.
* SQLEXPLAIN retrieves the message:
NULL values eliminated from the argument of an aggregate
function. (DBWARN 2041)
sqlwarn[3]
A W in sqlwarn[3] indicates that the number of host variables specified
in a dynamic SELECT or FETCH statement is unequal to the number of
columns in the table being operated on.
For example:
EXEC SQL PREPARE DynamicCommand from 'SELECT PartNumber, PartName
FROM PurchDB.Parts;';
.
EXEC SQL DESCRIBE DynamicCommand INTO SQLDA; /*sqlda.sqld is always set
at DESCRIBE by ALLBASE/SQL.*/
EXEC SQL DECLARE DynamicCursor FOR DynamicCommand;
EXEC SQL OPEN DynamicCursor;
.
/* Set up the sqlda for a fetch. */
sqlda.sqlbuflen=sizeof(DataBuffer);
sqlda.sqlnrow=((sqlbuflen)/(sqlrowlen));
sqlda.sqlrowbuf=&databuffer;
sqlda.sqld=1; / *sqlda.sqld is incorrectly reset by the program. */
.
/* Do the fetch. */
EXEC SQL FETCH DynamicCursor USING DESCRIPTOR SQLDA;
The FETCH will fail and the following occurs:
* sqlwarn[3] is set to W.
* sqlcode is set to -2762.
* SQLEXPLAIN retrieves the message:
Select list has ! items and host variable buffer has !.
(DBERR 2762)
sqlwarn[6]
When an error occurs that causes ALLBASE/SQL to roll back the current
transaction, sqlwarn[6] is set to W. ALLBASE/SQL automatically rolls back
transactions when sqlcode is equal to -4008, or equal to or less than
-14024.
When such errors occur, ALLBASE/SQL does the following:
* Sets sqlwarn[6] to W.
* Sets sqlwarn[0] to W.
* Sets sqlcode to a negative number.
If you want to terminate your program any time ALLBASE/SQL has to roll
back the current transaction, you can just test sqlwarn[6].
if (sqlca.sqlcode < 0) {
if (sqlca.sqlwarn[6] == 'W') {
SQLStatusCheck();
TerminateProgram();
}
else
SQLStatusCheck();
}
In this example, the program executes the function SQLStatusCheck when an
error occurs. The program terminates whenever ALLBASE/SQL has rolled
back a transaction, but continues if an error has occurred but was not
serious enough to cause transaction roll back.