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Understanding Nested TablesWithin the database, the nested tables can be considered as one-column database tables. The Oracle stores the rows of a nested table in no specific order. But, when you retrieve the nested table into the PL/SQL variable, the rows are given consecutive subscripts starting at 1. That provides you array-like access to the individual rows.Within PL/SQL, the nested tables are like one-dimensional arrays. Though, nested tables differ from arrays in two significant ways. Firstly, the arrays have a fixed upper bound, but nested tables are unbounded .Therefore, the size of a nested table can increase dynamically.
Figure: Array versus Nested TableSecondly, the arrays should be dense (having consecutive subscripts). Therefore, you cannot delete individual elements from an array. Initially, the nested tables are dense, but they can be sparse (having nonconsecutive subscripts). And hence, you can delete elements from a nested table using the built-in procedure DELETE. That might leave gaps in the index, but the built-in function NEXT iterate over any series of subscripts.
Cursor Variables As Parameters You can declare the cursor variables as the formal parameters of the functions and procedures. In the illustration below, you define the REF CUR
Parameter Aliasing To optimize the subprogram call, the PL/SQL compiler can decide between the two techniques of the parameter passing. With the by-value techniques, the v
Inserting Objects: You can use the INSERT statement to add objects to an object table. In the illustration below, you insert a Person object into the object table persons:
Ensuring Backward Compatibility The PL/SQL Version 2 permits some abnormal behavior which Version 8 disallows. Particularly, Version 2 permits you to (i) Make the forw
Assignment Source Not a Literal - Variable Syntax: SET SN = SID (SUBSTRING (SN.C FROM 1 FOR 1)||'5');
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
Explicit Cursors The set of rows returned by the query can include zero, one, or multiple rows, depending on how many rows meet your search criteria. Whenever a query returns
Projection in SQL - correct version Student StudentId is enrolled on some course. SELECT DISTINCT StudentId FROM IS_ENROLLED_ON In more complicated examples it is someti
Overriding Default Locking By default, the Oracle locks the data structures for you automatically. Though, you can request exact data locks on rows or tables when it is to you
Collection Methods: The collection method is a built-in function or procedure which operates on the collections and is called using the dot notation. The methods like the C
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