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Using Pragma RESTRICT_REFERENCES:
The function called from the SQL statements should obey certain rules meant to control the side effects. To check for violation of the rules, you can use the RESTRICT_REFERENCES pragma that instructs the compiler to report reads and/or writes to database tables and/or package variables.
Avoiding Deadlocks
In some situations when executing a SQL data definition statement, the outcome is a deadlock.
For illustration, the procedure below causes a deadlock as it attempts to drop itself. To avoid the deadlocks, never try to ALTER or DROP a subprogram or package while you are still using it.
CREATE PROCEDURE calc_bonus (emp_id NUMBER) AS
BEGIN
...
EXECUTE IMMEDIATE 'DROP PROCEDURE calc_bonus';
-- causes "timeout occur while waiting to the lock object" error
END;
Left and Right Joins LEFT OUTER JOIN can be used when you want to retrieve the data from the main table (table1) even if there is no match in other tables (table_2, table_3...
Grouping and Ungrouping in SQL Example specifying EXAM_MARK in place of COURSE in the main FROM clause. Example: Obtaining C_ER2 from EXAM_MARK SELECT CourseId, CAST
EXECUTE IMMEDIATE Statement The EXECUTE IMMEDIATE statement prepare (parses) and instantly executes a dynamic SQL statement or an anonymous PL/SQL block. Syntax:
Deleting Objects You can use the DELETE statement to eradicate objects from an object table. To eradicate objects selectively, you use the WHERE clause, as shown below: BEG
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
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
Definition of FROM - SQL Recall that the operand of FROM is denoted by a commalist, each element of that commalist being a table expression optionally accompanied by a range v
Use of Table Comparisons - SQL Table comparisons where it is noted that although table expressions cannot be compared, we have TABLE (t) to convert a table expression t into
Using the student and faculty tables create a select query that outputs all students for a specific advisor. Generate the execution plan, select out the explain plan . Create an
Keyword & Parameter Description: WHEN: This keyword introduces the exception handler. You can have many exceptions execute the similar sequence of the statements by follo
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