DBMS_XMLSTORE: Insert, Update, Delete XML data

Overview:
DBMS_XMLSTORE API / Package enables DML operations to be performed on relational tables using XML data.

Steps to use DBMS_XMLSTORE:

1. Create a context handle by calling function DBMS_XMLSTORE.newContext and supplying it with the table name to use for the DML operations. For case sensitivity, double-quote (“) the string that is passed to the function.

2. By default, XML documents are expected to use the tag to identify rows. This is the same default used by package DBMS_XMLGEN when generating XML data. You can use function setRowTag to override this behavior.

3. For inserts, to improve performance you can specify the list of columns to insert by calling procedure DBMS_XMLSTORE.setUpdateColumn for each column. The default behavior (if you do not specify the list of columns) is to insert values for each column whose corresponding element is present in the XML document.

4. For updates, use function DBMS_XMLSTORE.setKeyColumn to specify one or more (pseudo-) key columns, which are used to specify the rows to update. You do this in the WHERE clause of a SQL UPDATE statement. The columns that you specify need not be keys of the table, but together they must uniquely specify the rows to update.
For example, in table employees, column employee_id uniquely identifies rows (it is a key of the table). If the XML document that you use to update the table contains element <EMPLOYEE_ID>2176, then the rows where employee_id equals 2176 are updated.
To improve performance, you can also specify the list of update columns using DBMS_XMLSTORE.setUpdateColumn. The default behavior is to update all of the columns in the row(s) identified by setKeyColumn whose corresponding elements are present in the XML document.

5. For deletions you specify (pseudo-) key columns to identify the row(s) to delete. You do this the same way you specify rows to update — see step 3.

6. Provide a document to PL/SQL function insertXML, updateXML, or deleteXML. You can repeat this step to update several XML documents.

7. Close the context by calling function DBMS_XMLSTORE.closeContext.

Inserting with DBMS_XMLSTORE:

1 2	SELECT employee_id AS EMP_ID, salary, hire_date, job_id, email, last_name FROM employees WHERE department_id = 30;

Output:

EMP_ID SALARY HIRE_DATE JOB_ID EMAIL LAST_NAME
—— ———- ——— ———- ———- ———-
114 11000 07-DEC-94 PU_MAN DRAPHEAL Raphaely
115 3100 18-MAY-95 PU_CLERK AKHOO Khoo
116 2900 24-DEC-97 PU_CLERK SBAIDA Baida
117 2800 24-JUL-97 PU_CLERK STOBIAS Tobias
118 2600 15-NOV-98 PU_CLERK GHIMURO Himuro
119 2500 10-AUG-99 PU_CLERK KCOLMENA Colmenares

6 rows selected.

DECLARE

insCtx DBMS_XMLSTORE.ctxType;

rows NUMBER;

xmlDoc CLOB

:= ‘

<EMPLOYEE_ID>920

1800

<DEPARTMENT_ID>30

<HIRE_DATE>17-DEC-2002

<LAST_NAME>Satya

Venkata

<JOB_ID>ST_CLERK

<EMPLOYEE_ID>921

2000

<DEPARTMENT_ID>30

<HIRE_DATE>31-DEC-2004

<LAST_NAME>Vaddi

Kumar

<JOB_ID>ST_CLERK

‘ ;

BEGIN

insCtx := DBMS_XMLSTORE.newContext (‘HR.EMPLOYEES’); — Get saved context

DBMS_XMLSTORE.clearUpdateColumnList (insCtx); — Clear the update settings

— Set the columns to be updated as a list of values

DBMS_XMLSTORE.setUpdateColumn (insCtx, ‘EMPLOYEE_ID’);

DBMS_XMLSTORE.setUpdateColumn (insCtx, ‘SALARY’);

DBMS_XMLSTORE.setUpdateColumn (insCtx, ‘HIRE_DATE’);

DBMS_XMLSTORE.setUpdateColumn (insCtx, ‘DEPARTMENT_ID’);

DBMS_XMLSTORE.setUpdateColumn (insCtx, ‘JOB_ID’);

DBMS_XMLSTORE.setUpdateColumn (insCtx, ‘EMAIL’);

DBMS_XMLSTORE.setUpdateColumn (insCtx, ‘LAST_NAME’);

— Insert the doc.

rows := DBMS_XMLSTORE.insertXML (insCtx, xmlDoc);

DBMS_OUTPUT.put_line (rows || ‘ rows inserted.’);

— Close the context

DBMS_XMLSTORE.closeContext (insCtx);

END;

2 rows inserted.
PL/SQL procedure successfully completed.

1 2	SELECT employee_id AS EMP_ID, salary, hire_date, job_id, email, last_name FROM employees WHERE department_id = 30;

8 rows selected.

Updating with DBMS_XMLSTORE:

To update (modify) existing data using package DBMS_XMLSTORE, you must specify which rows to update. In SQL, you would do that using a WHERE clause in an UPDATE statement. With DBMS_XMLSTORE, you do it by calling procedure setKeyColumn once for each of the columns that are used collectively to identify the row.

You can think of this set of columns as acting like a set of key columns: together, they specify a unique row to be updated. However, the columns that you use (with setKeyColumn) need not be keys of the table — as long as they uniquely specify a row, they can be used with calls to setKeyColumn.

SELECT employee_id, first_name

FROM employees

WHERE employee_id = 188;

EMPLOYEE_ID FIRST_NAME
———– ———-
188 Kelly

1 row selected.

DECLARE

updCtx DBMS_XMLSTORE.ctxType;

rows NUMBER;

xmlDoc CLOB

:= ‘

<EMPLOYEE_ID>188

<FIRST_NAME>Dora

‘ ;

BEGIN

updCtx := DBMS_XMLSTORE.newContext (‘HR.EMPLOYEES’); — get the context

DBMS_XMLSTORE.clearUpdateColumnList (updCtx); — clear update settings

— Specify that column employee_id is a “key” to identify the row to update.

DBMS_XMLSTORE.setKeyColumn (updCtx, ‘EMPLOYEE_ID’);

rows := DBMS_XMLSTORE.UPDATEXML (updCtx, xmlDoc); — update the table

DBMS_XMLSTORE.closeContext (updCtx); — close the context

END;

SELECT employee_id, first_name

FROM employees

WHERE employee_id = 188;

EMPLOYEE_ID FIRST_NAME
———– ———-
188 Dora

1 row selected.

Deleting with DBMS_XMLSTORE:
Deletions are treated similarly to updates: you specify the key or pseudo-key columns that identify the rows to delete.

SELECT employee_id

FROM employees

WHERE employee_id = 188;

EMPLOYEE_ID
———–
188

1 row selected.

DECLARE

delCtx DBMS_XMLSTORE.ctxType;

rows NUMBER;

xmlDoc CLOB

:= ‘

<EMPLOYEE_ID>188

<DEPARTMENT_ID>50

‘ ;

BEGIN

delCtx := DBMS_XMLSTORE.newContext (‘HR.EMPLOYEES’);

DBMS_XMLSTORE.setKeyColumn (delCtx, ‘EMPLOYEE_ID’);

rows := DBMS_XMLSTORE.DELETEXML (delCtx, xmlDoc);

DBMS_XMLSTORE.closeContext (delCtx);

END;

SELECT employee_id

FROM employees

WHERE employee_id = 188;

no rows selected.