</programlisting>

</para>

<para>

Notice that this would be exactly equivalent to the following

statement because the <literal>MATCHED</literal> result does not change

during execution.

<programlisting>

MERGE INTO customer_account ca

USING (SELECT customer_id, transaction_value FROM recent_transactions) AS t

ON t.customer_id = ca.customer_id

WHEN MATCHED THEN

UPDATE SET balance = balance + transaction_value

WHEN NOT MATCHED THEN

INSERT (customer_id, balance)

VALUES (t.customer_id, t.transaction_value);

</programlisting>

</para>

<para>

Attempt to insert a new stock item along with the quantity of stock. If

the item already exists, instead update the stock count of the existing