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Nested Tables versus Index-by TablesThe Index-by tables and nested tables are just similar. For e.g. They have similar structure and their individual elements are accessed in the similar way (by using subscript notation). The main distinction is that the nested tables can be stored in a database column (and hence the word "nested table") while the index-by tables cannot.The Nested tables extend the functionality of the index-by tables by letting you SELECT,INSERT, DELETE, and UPDATE nested tables stored in the database. (Keep in mind, that index-by tables cannot be stored in the database). Some collection methods also operate only on the nested tables and varrays. For example, the built-in procedure TRIM cannot be applied to the index-by tables.Another merit of the nested tables is that an uninitialized nested table is automatically null (that is, the table itself is null, not its elements), while an uninitialized index-by table is simply empty. Therefore, you can apply the IS NULL comparison operator to the nested tables but not to index-by tables.Though, index-by tables also have some merits. For example, the PL/SQL supports implicit (automatic) datatype conversion between the host arrays and index-by tables (but not nested tables). Therefore, the most efficient way to pass collections to and from the database server is to use the anonymous PL/SQL blocks to bulk-bind input and output host arrays to the index-by tables.
Using the Collection Methods The collection methods below help to generalize the code and make collections easier to use and also make your applications easier to maintain:
UNION ALL - SQL Further varieties of UNION arise when we replace the key word DISTINCT by ALL in any of the foregoing examples, as in Example. ALL specifies that if row r appe
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Cursor Attributes The Cursors and cursor variables have 4 attributes which give you helpful information about the execution of a data manipulation statement. Syntax:
Using Savepoints The scope of the savepoint is a transaction in which it is defined. The Savepoints defined in the major transaction are not related to the savepoints defined
Using the BULK COLLECT Clause The keywords BULK COLLECT specify the SQL engine to bulk-bind output collections before returning them to the PL/SQL engine. You can use these ke
Hi there, I have the final part of a submission to do, it is a demonstration that takes place tomorrow. I do not have to use previous information, but i have resources that sho
Boolean Values Only the values TRUE, FALSE, & NULL can be assigned to a Boolean variable. For illustration, given the declaration DECLARE done BOOLEAN; the following statements
Example of GROUP BY and COLLECT Operator Example: Using GROUP BY and COLLECT to obtain C_ER2 SELECT CourseId, CAST ( COLLECT (ROW (StudentId, Mark)) AS ROW (Studen
Procedures The procedure is a subprogram which can take parameters and be invoked. Normally, you can use a procedure to perform an action. The procedure has 2 sections: the spe
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