Oracle trigger updating predicate multiple columns
In this post we will learn about Oracle XMLTable function. This way you can quickly understand different aspect of the API.
Now we can use Oracle XMLTable function to retrieve different information from this XML. Before we start with Oracle XMLTable function it is good to know a bit about XPath.
The MERGE statement basically merges data from a source result set to a target table based on a condition that you specify and if the data from the source already exists in the target or not. We can see the Coffee rate was updated from 20.00 to 25.00, the Muffin rate was updated from 30.00 to 35.00, Biscuit was deleted and Pizza was inserted.
The new SQL command combines the sequence of conditional INSERT, UPDATE and DELETE commands in a single atomic statement, depending on the existence of a record.
In a typical data warehousing application, quite often during the ETL cycle you need to perform INSERT, UPDATE and DELETE operations on a TARGET table by matching the records from the SOURCE table.
For example, a products dimension table has information about the products; you need to sync-up this table with the latest information about the products from the source table.
objects, assuming you’re working with a brand new database one thing you might want to do is issue CREATE statements for those tables and their related constructs (as an aside, it’s also quite possible that you want to do this, if you already have some preferred methodology such as tools included with your database or an existing scripting system - if that’s the case, feel free to skip this section - SQLAlchemy has no requirement that it be used to create your tables).
While it’s easy enough to emit ALTER statements and similar by hand, such as by passing a string to construct, it’s a common practice to automate the maintenance of database schemas in relation to application code using schema migration tools. XMLQuery lets you construct XML data and query XML and relational data using the XQuery language.XMLTable lets you create relational tables and columns from XQuery query results.accessor cannot by itself accommodate automatic resolution of dependency cycles between tables, which are usually caused by mutually dependent foreign key constraints.To resolve these cycles, either the Add a ‘dependency’ for this Table.
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In this tip we will walk through how to use the MERGE statement and do this in one pass.