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What Are Cursor Variables ?
The Cursor variables are like C or Pascal pointers that hold the memory location (address) of some item rather of the item itself. Therefore, declaring a cursor variable creates a pointer, not an item. In the PL/SQL, the pointer has a datatype REF X, where REF is short form for the REFERENCE and X stands for the class of objects. Therefore, a cursor variable has the datatype REF CURSOR.
To execute a multi-row query, the Oracle opens an unnamed work region which stores processing the information. To access the information, you can use an explicit cursor that names the work area. Or, you can use a cursor variable that points to the work region. While the cursor always refers to the similar query work region, a cursor variable can refer to various work regions. Therefore, the cursors and cursor variables are not interoperable.
SQL outer join SELECT * FROM IS_CALLED NATURAL LEFT JOIN IS_ENROLLED_ON Note that adding LEFT to an invocation of CROSS JOIN has no effect unless the right-hand operand
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SELECT INTO Statement The SELECT INTO statement retrieve data from one or more database tables, and then assigns the selected values to the variables or fields. Syntax:
Using COUNT The COUNT returns the number of elements that a collection presently contains. For instance, when a varray projects contains 15 elements, then the following IF con
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Avoid the NOT NULL Constraint In the PL/SQL, using the NOT NULL constraint incur a performance cost. Consider the illustration as shown below: PROCEDURE calc_m IS m NUMB
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Avoiding Collection Exceptions In many cases, if you reference a nonexistent collection element, then PL/SQL raises a predefined exception. Consider the illustration shown b
Effects of NULL in Aggregate Operator - SQL Let aggop(x) be an invocation of some aggregate operator aggop in SQL, where x is an expression (usually an open expression) to be
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