How to deal with sequence in insert from XMLTable? - oracle

Question

I have write a PL/SQL function that takes input in XML format for the
following table:
TABLE: TBL_MEDICAL_CENTER_BILLS
Name Null Type
------------- -------- -------------
MED_RECORDNO NOT NULL NUMBER
MED_EMPID NVARCHAR2(10)
MED_BILL_HEAD NVARCHAR2(20)
MED_DATE DATE
MED_AMOUNT FLOAT(126)
Here is the function code:
FUNCTION save_medical_center_bills(medical_bill_data NVARCHAR2 ) RETURN clob IS ret clob;
xmlData XMLType;
v_code NUMBER;
v_errm VARCHAR2(100);
BEGIN
xmlData:=XMLType(medical_bill_data);
INSERT INTO TBL_MEDICAL_CENTER_BILLS SELECT x.* FROM XMLTABLE('/medical_center_bill'
PASSING xmlData
COLUMNS MED_RECORDNO NUMBER PATH 'MED_RECORDNO' default null,
MED_EMPID NVARCHAR2(11) PATH 'employee_id',
MED_BILL_HEAD NVARCHAR2(20) PATH 'bill_head' ,
MED_DATE DATE PATH 'effective_date',
MED_AMOUNT FLOAT PATH 'bill_amount'
) x;
ret:=to_char(sql%rowcount);
COMMIT;
RETURN '<result><status affectedRow='||ret||'>success</status></result>';
EXCEPTION
WHEN OTHERS THEN
v_code := SQLCODE;
v_errm := SUBSTR(SQLERRM, 1, 100);
DBMS_OUTPUT.PUT_LINE (v_code || ' ' || v_errm);
-- '<result><status>Error</status> <error_message>'|| 'Error Code:' || v_code || ' ' || 'Error Message:' || v_errm ||'</error_message> </result>';
RETURN '<result><status>Error</status> <error_message>'|| 'Error Message:' || v_errm ||'</error_message> </result>';
END save_medical_center_bills;
However, I want to keep table's first column MED_RECORDNO as incrementing sequence (at the moment I am keeping it null since I don't know how to put the sequence in the XMLTable clause) and the rest of the
inputs [MED_EMPID, MED_BILL_HEAD , MED_DATE , MED_AMOUNT] will be taken from the XML passed to the function.
I created a sequence and a trigger to keep this sequence incremented for that table column MED_RECORDNO:
CREATE SEQUENCE MED_RECORDNO_SEQ;
create or replace TRIGGER MED_RECORDNO_TRIGGER
BEFORE INSERT ON TBL_MEDICAL_CENTER_BILLS FOR EACH ROW
WHEN (new.MED_RECORDNO is null)
DECLARE
v_id TBL_MEDICAL_CENTER_BILLS.MED_RECORDNO%TYPE;
BEGIN
SELECT MED_RECORDNO_seq.nextval INTO v_id FROM DUAL;
:new.MED_RECORDNO := v_id;
END;
As you can see, my XMLTable is inserting 4 column values in a 5 column table, because columns MED_RECORDNO will take its value from sequence MED_RECORDNO_SEQ using TRIGGER MED_RECORDNO_TRIGGER.
I don't know any thing about doing this. If you have ever experience such things, then please share your idea.

Answer 1

I sort of hinted at this in an earlier answer. You should specify the names of of the columns in the table you are inserting into; this is good practice even if you are populating all of them, as it will avoid surprises if the table structure changes (or differs between environments), and makes it much easier to spot like having columns or values in the wrong order.
INSERT INTO TBL_MEDICAL_CENTER_BILLS (MED_EMPID, MED_BILL_HEAD, MED_DATE, MED_AMOUNT)
SELECT x.MED_EMPID, x.MED_BILL_HEAD, x.MED_DATE, x.MED_AMOUNT
FROM XMLTABLE('/medical_center_bill'
PASSING xmlData
COLUMNS MED_EMPID NVARCHAR2(11) PATH 'employee_id',
MED_BILL_HEAD NVARCHAR2(20) PATH 'bill_head' ,
MED_DATE DATE PATH 'effective_date',
MED_AMOUNT FLOAT PATH 'bill_amount'
) x;
The insert you have should actually work (if the column order in the table matches); the trigger will still replace the null value you get from the XMLTable with the sequence value. At least, until you make the MED_RECORDNO column not-null, and you probably want to if it's the primary key.
Incidentally, if you're on 11g or higher your trigger can assign the sequence straight to the NEW pseudorecord:
create or replace TRIGGER MED_RECORDNO_TRIGGER
BEFORE INSERT ON TBL_MEDICAL_CENTER_BILLS
FOR EACH ROW
BEGIN
:new.MED_RECORDNO := MED_RECORDNO_seq.nextval;
END;
The when null check implies you sometimes want to allow a value to be specified; that is a bad idea as manually inserted values can clash with sequence values, either giving you duplicates or a unique/primary key exception.