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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;
SQLs counterpart of the key words: The text from the opening parenthesis to the end of the fourth line specifies the declared type of the table, meaning that every table ever
Relational Operators The relational operators permit you to compare randomly complex expressions. The list below provides the meaning of each operator:
Nested Tables versus Index-by Tables The Index-by tables and nested tables are just similar. For e.g. They have similar structure and their individual elements are accessed in
Updating Objects: To change the attributes of objects in an object table, you can use the UPDATE statement, as the illustration below shows: BEGIN UPDATE persons p SET p
which operation is used if we are interested in only certain columns of a table?
Using %ROWTYPE The %ROWTYPE attribute gives a record type which represents a row in a table (or view). The record can store the whole row of data selected from the table or fetc
Projection and Existential Quantification - SQL Intuitively it might seem that projection in SQL is simply a matter of specifying the required columns in the SELECT clause, a
Literals A literal is an explicit numeric, string, character, or Boolean value not represented by an identifier. Numeric literal 147 and the Boolean literal FALSE are some of
Package STANDARD The package named STANDARD defines the PL/SQL atmosphere. The package specification globally declares the exceptions, types, and subprograms that are available
Scope and Visibility The References to an identifier are resolved according to its visibility and scope. The scope of an identifier is that area of a program unit (subprogram, b
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