SIGNAL statement

id="signalstmt">SIGNAL statement

The SIGNAL statement signals an error or warning condition. It causes an error or warning to be returned with the specified SQLSTATE and optional condition-information-items. The syntax of SIGNAL in an SQL function, SQL procedure, or SQL trigger is a similar to what is supported as a SIGNAL statement in other contexts. See SIGNAL for details.

Syntax
                                 .-VALUE-.
>>-+--------+-SIGNAL-+-SQLSTATE--+-------+--+-sqlstate-string-constant-+-+-->
   '-label:-'        |                      '-sqlstate-string-variable-' |
                     '-condition-name------------------------------------'
 
>--+--------------------+--------------------------------------><
   '-signal-information-'
 
signal-information:  
          .-,-----------------------------------------------------------.
          V                                                             |
|--+-SET----+-MESSAGE_TEXT-------+-- = --+-SQL-variable-name----------+-+-+--|
   |        +-CONSTRAINT_CATALOG-+       +-SQL-parameter-name---------+   |
   |        +-CONSTRAINT_SCHEMA--+       '-diagnostic-string-constant-'   |
   |        +-CONSTRAINT_NAME----+                                        |
   |        +-CATALOG_NAME-------+                                        |
   |        +-SCHEMA_NAME--------+                                        |
   |        +-TABLE_NAME---------+                                        |
   |        +-COLUMN_NAME--------+                                        |
   |        +-CURSOR_NAME--------+                                        |
   |        +-CLASS_ORIGIN-------+                                        |
   |        '-SUBCLASS_ORIGIN----'                                        |
   '-(--diagnostic-string-constant--)-------------------------------------'
 
Description
label

Specifies the label for the SIGNAL statement. The label name cannot be the same as the routine name or another label within the same scope. For more information, see Labels.

SQLSTATE VALUE

Specifies the SQLSTATE that will be signalled. The specified value must not be null and must follow the rules for SQLSTATEs:

Each character must be from the set of digits ('0' through '9') or non-accented upper case letters ('A' through 'Z').

The SQLSTATE class (first two characters) cannot be '00' since this represents successful completion.

If the SQLSTATE does not conform to these rules, an error is returned.

sqlstate-string-constant

The sqlstate-string-constant must be a character string constant with exactly 5 characters.

sqlstate-string-variable

The sqlstate-string-variable must be a character or Unicode graphic variable. The actual length of the contents of the variable must be 5.

condition-name

Specifies the name of the condition that will be signalled. The condition-name must be declared within the compound-statement.

SET

Introduces the assignment of values to condition-information-items. The condition-information-item values can be accessed using the GET DIAGNOSTICS statement. The only condition-information-item that can be accessed in the SQLCA is MESSAGE_TEXT.

MESSAGE_TEXT

Specifies a string that describes the error or warning.
If an SQLCA is used,

the string is returned in the SQLERRMC field of the SQLCA

if the actual length of the string is longer than 70 bytes, it is truncated without a warning.

CONSTRAINT_CATALOG

Specifies a string that indicates the name of the database that contains a constraint related to the signalled error or warning.

CONSTRAINT_SCHEMA

Specifies a string that indicates the name of the schema that contains a constraint related to the signalled error or warning.

CONSTRAINT_NAME

Specifies a string that indicates the name of a constraint related to the signalled error or warning.

CATALOG_NAME

Specifies a string that indicates the name of the database that contains a table or view related to the signalled error or warning.

SCHEMA_NAME

Specifies a string that indicates the name of the schema that contains a table or view related to the signalled error or warning.

TABLE_NAME

Specifies a string that indicates the name of a table or view related to the signalled error or warning.

COLUMN_NAME

Specifies a string that indicates the name of a column in the table or view related to the signalled error or warning.

CURSOR_NAME

Specifies a string that indicates the name of a cursor related to the signalled error or warning.

CLASS_ORIGIN

Specifies a string that indicates the origin of the SQLSTATE class related to the signalled error or warning.

SUBCLASS_ORIGIN

Specifies a string that indicates the origin of the SQLSTATE subclass related to the signalled error or warning.

SQL-variable-name

Identifies an SQL variable declared within the compound-statement, that contains the value to be assigned to the condition-information-item. The SQL variable must be defined as CHAR, VARCHAR, Unicode GRAPHIC, or Unicode VARGRAPHIC variable.

SQL-parameter-name

Identifies an SQL parameter declared within the compound-statement, that contains the value to be assigned to the condition-information-item. The SQL parameter must be defined as CHAR, VARCHAR, Unicode GRAPHIC, or Unicode VARGRAPHIC variable.

diagnostic-string-constant

Specifies a character string constant that contains the value to be assigned to the condition-information-item.

( diagnostic-string-constant )
Specifies a character string constant that contains the message text. Within the triggered action of a CREATE TRIGGER statement, the message text can only be specified using this syntax:
 SIGNAL SQLSTATE sqlstate-string-constant (diagnostic-string-constant);
To conform with the ANS and ISO standards, this form should not be used. It is provided for compatibility with other products.
Notes

SQLSTATE values: Any valid SQLSTATE value can be used in the SIGNAL statement. However, it is recommended that programmers define new SQLSTATEs based on ranges reserved for applications. This prevents the unintentional use of an SQLSTATE value that might be defined by the database manager in a future release.
SQLSTATE values are comprised of a two-character class code value, followed by a three-character subclass code value. Class code values represent classes of successful and unsuccessful execution conditions.

SQLSTATE classes that begin with the characters '7' through '9' or 'I' through 'Z' may be defined. Within these classes, any subclass may be defined.

SQLSTATE classes that begin with the characters '0' through '6' or 'A' through 'H' are reserved for the database manager. Within these classes, subclasses that begin with the characters '0' through 'H' are reserved for the database manager. Subclasses that begin with the characters 'I' through 'Z' may be defined.

For more information about SQLSTATEs, see the SQL Messages and Codes book in the i5/OS Information Center.
Assignment: When the SIGNAL statement is executed, the value of each of the specified string-constants, SQL-parameter-names, and SQL-variable-names is assigned (using storage assignment) to the corresponding condition-information-item. For details on the assignment rules, see Assignments and comparisons. For details on the maximum length of specific condition-information-items, see GET DIAGNOSTICS.
Processing a SIGNAL statement: When a SIGNAL statement is issued, the SQLCODE returned in the SQLCA is based on the SQLSTATE value as follows:

If the specified SQLSTATE class is either '01' or '02', a warning or not found is signalled and the SQLCODE is set to +438.

Otherwise, an exception is signalled and the SQLCODE is set to –438.

If the SQLSTATE or condition indicates that an exception (SQLSTATE class other than '01' or '02') is signalled,

If a handler exists in the same compound statement as the SIGNAL statement, and the compound statement contains a handler for SQLEXCEPTION or the specified SQLSTATE or condition; the exception is handled and control is transferred to that handler.

If the compound-statement is nested and an outer level compound-statement has a handler for SQLEXCEPTION or the specified SQLSTATE or condition; the exception is handled and control is transferred to that handler.

Otherwise, the exception is not handled and control is immediately returned to the end of the compound statement.

If the SQLSTATE or condition indicates that a warning (SQLSTATE class '01') or not found (SQLSTATE class '02') is signalled,

If a handler exists in the same compound statement as the SIGNAL statement, and the compound statement contains a handler for SQLWARNING (if the SQLSTATE class is '01'), NOT FOUND (if the SQLSTATE class is '02'), or the specified SQLSTATE or condition; the warning or not found condition is handled and control is transferred to that handler.

If the compound-statement is nested and an outer level compound statement contains a handler for SQLWARNING (if the SQLSTATE class is '01'), NOT FOUND (if the SQLSTATE class is '02'), or the specified SQLSTATE or condition; the warning or not found condition is handled and the exception is handled and control is returned to that handler.

Otherwise, the warning is not handled and processing continues with the next statement.

Affects on the diagnostic area: The SIGNAL statement starts with a clear diagnostics area and sets the RETURNED_SQLSTATE to reflect the SQLSTATE or condition name specified.

Example

An SQL procedure for an order system that signals an application error when a customer number is not known to the application. The ORDERS table includes a foreign key to the CUSTOMER table, requiring that the CUSTNO exist before an order can be inserted.
   CREATE PROCEDURE SUBMIT_ORDER       (IN ONUM INTEGER, IN CNUM INTEGER,
       IN PNUM INTEGER, IN QNUM INTEGER)
       LANGUAGE SQL        MODIFIES SQL DATA       BEGIN
         DECLARE EXIT HANDLER FOR SQLSTATE VALUE '23503'
            SIGNAL SQLSTATE '75002'
               SET MESSAGE_TEXT = 'Customer number is not known';
         INSERT INTO ORDERS (ORDERNO, CUSTNO, PARTNO, QUANTITY)
            VALUES (ONUM, CNUM, PNUM, QNUM); 	
      END
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