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Use the RETURNING Clause
Frequently, the application requires information about the row affected by a SQL operation, for illustration, to produce a report or take a subsequent action. The INSERT, UPDATE, & DELETE statements can involve a RETURNING clause that returns column values from the affected row into the PL/SQL variables or host variables. This removes the requirement to SELECT the row after an insert or update, or before a delete. As a result, less network round trips, less server CPU time, smaller number of cursors, and less server memory are needed.
In the illustration below, you update the salary of an employee and at similar time retrieve the employee's name and new salary into the PL/SQL variables.
PROCEDURE update_salary (emp_id NUMBER) IS
name VARCHAR2(15);
new_sal NUMBER;
BEGIN
UPDATE emp SET sal = sal * 1.1
WHERE empno = emp_id
RETURNING ename, sal INTO name, new_sal;
Datatype Conversion At times it is necessary to convert a value from one datatype to another. For e.g. if you want to inspect a rowid, you should convert it to a character stri
Closing a Cursor The CLOSE statements disable the cursor, and the result set becomes undefined. An illustration of the CLOSE statement as shown: CLOSE c1;
Using a Host Variable You can declare the cursor variable in the PL/SQL host environment like an OCI or Pro C program. To use the cursor variable, you should pass it as a host
Using FOR UPDATE If you declare a cursor which will be referenced in the CURRENT OF clause of an UPDATE or DELETE statement, you should use the FOR UPDATE clause to obtain an
Bulk Fetching The illustration below shows that you can bulk-fetch from a cursor into one or more collections: DECLARE TYPE NameTab IS TABLE OF emp.ename%TYPE; TYPE S
Existential Quantification - SQL Existential quantification-stating that something is true of at least one object under consideration-can be expressed by OR(r,c), meaning tha
Tables within a Table - SQL Figure here is an exact copy of the one in the theory book and as before it is just an alternative way of representing some of the information con
Inner Join We have learned how to retrieve data from one table by using SELECT statement. But, as we have learned, normalized relational databases mean the data is spread betw
Data Types in SQL SQL's concept does not differ significantly from that defined in the theory book, apart from that business concerning NULL. However, the theory book equates
Important Distinctions The list of important distinctions are given below: Value versus variable Syntax versus semantics Variable versus variable reference
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