We have a Chinese version(http://scn.sap.com/community/chinese/hana/blog/2014/04/02/sap-hana-sqlscript-procedure%E4%B8%AD%E7%9A%84%E5%BC%82%E5%B8%B8%E5%A4%84%E7%90%86) of this document.

     For SQL procedure using SQLScript, SAP HANA provides corresponding methods of exception handling. There are three tools can be used: EXIT HANDLER, CONDITION, SIGNAL or RESIGANL.

     An example using EXIT HANLEDR shows as follows.

CREATETABLE MYTAB (I INTEGERPRIMARYKEY); 
CREATE PROCEDURE MYPROC1 
AS BEGIN
DECLARE EXIT HANDLER FOR SQLEXCEPTION SELECT ::SQL_ERROR_CODE, ::SQL_ERROR_MESSAGE FROM DUMMY;
INSERT INTO MYTAB VALUES (1); 
INSERT INTO MYTAB VALUES (1); -- expected unique violation error: 301 
END; 

     When invoking this procedure, an exception of violating unique constraint will be thrown, for inserting the same content on primary key. Then the invocation well be suspended, and the subsequent operations will not be executed. After suspending the procedure, the action operations of EXIT HANDLER will be executed.

     Notice: We can use  "::SQL_ERROR_CODE","::SQL_ERROR_MESSAGE" to get the SQL ERROR CODE and related error message of the caught exception.

EXIT HANDLER

When declare an EXIT HANDLER in SQLScript Procedure, the syntax shows as below.

DECLARE EXIT HANDLER FOR <proc_condition_value_list> <proc_stmt>;<proc_condition_value_list> ::= <condition_value> [ { <comma> <condition_value> }... ]<condition_value> ::= <sql_error_code> | <condition_name> | SQLEXCEPTION<sql_error_code> ::= SQL_ERROR_CODE <numeric_literal>

     We can declare an EXIT HANDLER to handle exceptions of the given SQL ERROR CODE or user defined condition in SQL procedures and provide the subsequent operations after the exception is thrown.

Notice：

SAP HANA provides common SQL error code：

http://help.sap.com/saphelp_hanaplatform/helpdata/en/20/a78d3275191014b41bae7c4a46d835/content.htm

or check“SAP HANA SQL and System Views Reference”->1.10  SQL Error Codes

CONDITION

     You can declare a CONDITION in SQL procedure to define a condition which contains a SAP HANA error code or used-defined error code and name it. Then you can declare an EXIT HANDLER to handle exception of this condition, or use SIGNAL or RESIGNAL to throw an exception of a condition containing a user-defined error code.

     The syntax of CONDITION declaration：

DECLARE <condition name> CONDITION [ FOR <sql_error_code> ];<sql_error_code> ::= SQL_ERROR_CODE <numeric_literal>

SIGNAL/RESIGNAL

     SIGNAL or RESIGNAL can be used to throw exception in SQL procedure. But here exception only represents used-defined error, whose error code is between 10000 and 19999.

     The difference between SIGNAL and RESIGNAL is that when using SIGNAL, you must point out the SQL ERROR CODE or CONDITION of the exception. But RESIGNAL can be used in the action part of an EXIT HANDLER all alone. That is to say, RESIGNAL can be used to throw exception of the EXIT HANDLER catches to the caller. A user-defined exception can be catch by the corresponding EXIT HANDLER, or caught by the caller, same as an exception contains error code.

The syntax of using SINGAL or RESIGNAL：

SIGNAL <signal_value> [<set_signal_information>] ;
RESIGNAL [<signal_value>] [<set_signal_information>];<signal_value> ::= <condition_name> | <sql _error_code><set_signal_information> ::= SET <signal_information_item><signal_information_item> ::= MESSAGE_TEXT  <equals operator> <simple_value_specification><simple_value_specification> ::= <procedure_expression>

Examples

1.General exception handling

CREATETABLE MYTAB (I INTEGER PRIMARYKEY); 
CREATE PROCEDURE MYPROC 
AS BEGIN     DECLARE EXIT HANDLER FOR SQLEXCEPTION        SELECT ::SQL_ERROR_CODE, ::SQL_ERROR_MESSAGE FROM DUMMY;    INSERT INTO MYTAB VALUES (1);     INSERT INTO MYTAB VALUES (1); -- expected unique violation error: 301     -- will not be reached 
END; 
CALL MYPROC;

2.Error code exception handling

CREATETABLE MYTAB (I INTEGERPRIMARYKEY);
CREATE PROCEDURE MYPROC 
AS BEGIN    DECLARE myVar INT;    DECLARE EXIT HANDLER FOR SQL_ERROR_CODE 1299       SELECT ::SQL_ERROR_CODE, ::SQL_ERROR_MESSAGE FROM DUMMY;    SELECT I INTO myVar FROM MYTAB; --NO_DATA_FOUND exception
END;
CALL MYPROC;

The error message of SQL ERROR CODE 1299 is ”No data found”.

3.Conditional Exception Handling

CREATETABLE MYTAB (I INTEGERPRIMARYKEY);
CREATE PROCEDURE MYPROC 
AS BEGIN    DECLARE MYCOND CONDITION FOR SQL_ERROR_CODE 301;    DECLARE EXIT HANDLER FOR MYCOND         SELECT ::SQL_ERROR_CODE, ::SQL_ERROR_MESSAGE FROM DUMMY;    INSERT INTO MYTAB VALUES (1);    INSERT INTO MYTAB VALUES (1); -- expected unique violation error: 301    -- will not be reached
END;
CALL MYPROC;

4.Throw an exception using SIGNAL

CREATEPROCEDURE MYPROC 
AS BEGIN    DECLARE MYCOND CONDITION FOR SQL_ERROR_CODE 10001;    DECLARE EXIT HANDLER FOR MYCOND         SELECT ::SQL_ERROR_CODE, ::SQL_ERROR_MESSAGE FROM DUMMY;    SIGNAL MYCOND SET MESSAGE_TEXT = 'my error';    -- will not be reached
END;
CALL MYPROC;

5.Throw an exception using RESIGNAL

CREATEPROCEDURE MYPROC 
AS BEGIN    DECLARE MYCOND CONDITION FOR SQL_ERROR_CODE 10001;    DECLARE EXIT HANDLER FOR MYCOND RESIGNAL;    SIGNAL MYCOND SET MESSAGE_TEXT = 'my error';    -- will not be reached
END;
CALL MYPROC;

6.When using EXIT HANLDER, related tables can be used to store the exception information.

CREATETABLE ERROR_LOG
(ERROR_CODE VARCHAR(5),
 ERROR_MSG VARCHAR(200),
 TIME_STAMP TIMESTAMP);
CREATE PROCEDURE MYPROC 
AS BEGIN
DECLARE MYCOND CONDITION FOR SQL_ERROR_CODE 10001;
DECLARE EXIT HANDLER FOR MYCOND signal mycond set message_text = 'error'; 
 SIGNAL MYCOND;
-- will not be reached
END;
CREATE PROCEDURE MYPROC1 
AS BEGIN
DECLARE EXIT HANDLER FOR sqlexception
INSERT INTO ERROR_LOG VALUES(::SQL_ERROR_CODE, ::SQL_ERROR_MESSAGE,CURRENT_TIMESTAMP);
CALL MYPROC;
END;    
CALL MYPROC1;