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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.
LIKE Operator You use the LIKE operator to compare the character value to a pattern. The Case is significant. LIKE returns the Boolean value TRUE when the character patterns mat
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Parameter and Keyword Description: collection_name: This keyword identifies the index-by table, nested table, or varray formerly declared within the present scope. cu
Using DELETE This process has three forms. The DELETE removes all elements from the collection. DELETE(n) removes the nth element from the nested table. When n is null, then D
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Example of NOT EXISTS in SQL Example: Use of NOT EXISTS CREATE ASSERTION Must_be_enrolled_to_take_exam_alternative1 CHECK ( NOT EXISTS (SELECT StudentId, CourseId
Using Aliases The Select-list items fetched from a cursor related with the %ROWTYPE should have simple names or, if they are expressions, should have aliases. In the example bel
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