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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;
Effect of Anonymous Columns Now, recall that a VALUES expression denotes a table with undefined column names. If an initial value is to be specified when a base table is creat
Question: Consider the following relations (primary keys are underlined): AUTHOR (ANo, aname, address, speciality) PUBLISHER (PNo, pname, Location) BOOK (BNo, Title, ISBN,
Quantification in SQL To quantify something, as the theory book has it, is to state its quantity, to say how many of it there are. For example, in Tutorial D the expression CO
Tautologies: Above given table allows us to read the truth of the connectives in the next manner. Just expect we are looking at row three. It means this says that, if there P
1- You can check attribute names from each table in DBF11 by running for example: desc dbf11.Member; desc dbf11.Agent; desc dbf11.Producer; Because some attribute names in
LOB Types The large object (LOB) datatypes like BFILE, BLOB, CLOB, and NCLOB store the blocks of unstructured data (like graphic images, text, video clips, and sound waveforms)
Negation (NOT, ¬) - SQL There are three rows instead of just two. As you can see, ¬ p is defined as in two-valued logic (2VL) when p is either true or false, but ¬ (unknown) i
CLOSE Statement The CLOSE statement allows the resources held by a cursor variable or open cursor to be reused. No more rows can be fetched from the cursor variable or closed
Example of Foreign Key Constraint Example: Alternative formulation for 6.3 as a foreign key constraint ALTER TABLE EXAM_MARK ADD CONSTRAINT Must_be_enrolled_to_take_exam
Query: SELECT * FROM EMPLOYEE1; Select 5 columns and all rows from one table Query: SELECT C_ID, COMPANY, BUILDING, DEPARTMENT, BRANCH FROM CONTRACT;
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