How to update xml data type in oracle

These days, we store all data in the relational model with a dynamic column structure. However, early data models may not fit with the relational model. However, it raised XML validation issues. Indeed, even with an XML data type, we confronted numerous performance issues. For example, querying with an XML tag, performing data manipulations within a document or other documents in the same table or cross table, or making updates resulted in cumbersome XML. The main problem was the cost of parsing the fragment each time it was accessed.

As an industry-standard, we need to store unstructured data in a database, where the end-user chooses the structure of information. Unfortunately, this is a tedious way to manage and apply logic or metrics to unstructured information. That is, a copy of the targeted nodes is returned, not a reference to the actual nodes. When the returned sequence is passed by value, the columns specified in a COLUMNS clause cannot refer to any data that is not in that returned copy. In particular, they cannot refer to data that precedes the targeted nodes in the source data.

Because the sequence of LineItem nodes is returned by reference, the code has access to the complete tree of nodes, so it can navigate upward and then back down to node Reference.

Example illustrates this. For column reference of the top-level table, t1 , because it corresponds to a node outside element LineItem just as in Example For column part of table t1 , because it is passed to table t2 , whose column item targets data outside node Part. Without specifying that part is a reference, it would be a copy of just the Part element, so that using PATH expression.. You can use the XQuery declare namespace declaration in the prolog of an XQuery expression to define a namespace prefix.

You can use declare default namespace to establish the namespace as the default namespace for the expression. To avoid this, you can do one of the following:. Place a comment, such as : : , after the semicolon, on the same line.

Example illustrates use of a namespace declaration in an XQuery expression. An XQuery namespace declaration has no effect outside of its XQuery expression. It uses a local XMLType instance to store transient data. They then insert that data into a relational table. Example tabulates the purchase orders whose shipping address contains the string " Shores " and which were requested by customers whose names contain the string " ll " double L.

These purchase orders are grouped by customer and counted. The example uses XQuery Full Text to perform full-text search. Example extracts the fragments of a document that are identified by an XPath expression. You cannot insert fragments into XMLType columns. Execution is identical, with the same optimizations. A typical use case for this feature is to access data stored in remote databases from a local Java program. These are then passed to XQuery as XQuery variables itemno and id , respectively.

NET and the C language. The C input parameters :nbitems and :partid are passed to XQuery as XQuery variables itemno and id , respectively. This can be created in any of the following ways:. The entire document is updated, not just the part of it that is selected. In real-world examples you will typically pass a value that is available only at runtime; Example shows how to do that.

This is also true of other examples. Example updates multiple text nodes and attribute nodes. Example updates selected nodes within a collection. Example illustrates the common mistake of using an XQuery Update replace-value operation to update a node that occurs multiple times in a collection.

Instead of updating only the intended node, Example updates the values of all text nodes that belong to the Description element. This is not what was intended. A WHERE clause can be used only to identify which documents must be updated, not which nodes within a document must be updated.

After the document has been selected, the XQuery expression passed to XQuery Update determines which nodes within the document must be updated. In this case, the XQuery expression identifies all three Description nodes, so all three of the associated text nodes were updated. To correctly update a node that occurs multiple times within a collection, use the XQuery expression passed XQuery Update to identify which nodes in the XML document to update.

By introducing the appropriate predicate into the XQuery expression, you can limit which nodes in the document are updated.

Example illustrates the correct way to update one node within a collection. The type and namespace properties of the element are retained. See Example If you update an attribute value to NULL , the value appears as the empty string. If you update the text node of an element to NULL , the content text of the element is removed. The element itself remains, but it is empty. Example updates all of the following to NULL :.

The Description element and the Quantity attribute of the LineItem element whose Part element has attribute Id value Note that Example shows two different but equivalent ways to remove the value of a node. For element Description and attribute Quantity , a literal XQuery empty sequence, , replaces the existing value directly.

But in real-world examples you will often pass a value that is available only at runtime. You can use XQuery Update to insert new children either a single attribute or one or more elements of the same type under parent XML elements. The XML document that is the target of the insertion can be schema-based or non-schema-based.

Example inserts a new LineItem element as a child of element LineItems. Note that it uses the Oracle XQuery pragma ora:child-element-name to specify the name of the inserted child element as LineItem. If the XML data to be updated is XML schema-based and it refers to a namespace, then the data to be inserted must also refer to the same namespace.

Otherwise, an error is raised because the inserted data does not conform to the XML schema. Be aware that using XQuery Update to update XML schema-based data results in an error being raised if you try to store the updated data back into an XML schema-based column or table. Example is the same as Example , except that the LineItem element to be inserted refers to a namespace.

This assumes that the relevant XML schema requires a namespace for this element. Example inserts a LineItem element before the first LineItem element. You can also use a variety of other functions that return XMLType.

You can select out the XMLType instance from the column. XMLType also offers a choice of member functions, such as extract and existsNode , to extract a particular node and to check to see if a node exists respectively. This helps existsNode implement indexing and optimizes the evaluation of existsNode in a predicate. Hence you can also specify LOB storage characteristics for that column. You can specify storage characteristics on this column when creating the table as follows:.

The same holds for XML schema-based storage. You can also define check constraints on XMLType columns. Other default values are not supported on this datatype. You can use XMLType wherever you use a user-defined type, including for table columns, views, trigger bodies, and type definitions.

You can create the insertable XML documents as follows:. Assume that the purchase order is an object view that contains a purchase order object. XMLType datatype supports most of these as member functions. You can use either the selfish style of invocation or the SQL functions.

Both these functions use a subset of the W3C XPath recommendation to navigate the document. XPath models the XML document as a tree of nodes. It provides a rich set of operations to "walk" the tree and to apply predicates and node test functions. Table lists some common constructs used in XPath. Denotes the root of the tree in an XPath expression. Also used as a path separator to identify the children node of any given node.

Used to identify all descendants of the current node. Used as a wildcard to match any child node. Used to denote predicate expressions. The XPath must identify a single or a set of element, text, or attribute nodes. The result of the XPath cannot be a boolean expression. The syntax for the existsNode function is described in Figure and also as follows:.

If so, it returns the numeric value 1, otherwise, it returns a 0. Therefore, existsNode will return 1 for that XPath. Therefore, an existsNode on this would return the value 0.

To summarize, existsNode member function can be used in queries and to create function-based indexes to speed up evaluation of queries. You can create function-based indexes using existsNode to speed up the execution. The extract f unction is similar to the e xistsNode function. The syntax is described in Figure and as follows:. The extracted nodes can be elements, attributes, or text nodes. When extracted out, all text nodes are collapsed into a single text node value. Namespace can be used to supply namespace information for prefixes in the XPath string.

The latter is still considered an XMLType. Use text node test function to identify text nodes in elements before using the getStringVal or getNumberVal to convert them to SQL data. Not having the text node would produce an XML fragment. You can use the index mechanism to identify individual elements in case of repeated elements in an XML document. For example, if you have an XML document such as:.

The result of extract is always an XMLType. Hence, extract member function can be used in a number of ways, including the following:.

It is an ease-of-use and shortcut function. So instead of using:. With extractValue you can leave off the text , but ONLY if the node pointed to by the ' path ' part has only one child and that child is a text node. Otherwise, an error is thrown.