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Varrays versus Nested TablesThe Nested tables are differing from varrays in the following ways:1) Varrays have a maximum size, while nested tables do not.2) Varrays are always dense, while nested tables can be sparse. Therefore, you can delete individual elements from a nested table but not from a varray.3) The Oracle stores varray data in-line (in similar tablespace). But, the Oracle stores nested table data out-of-line in a store table, that is a system-generated database table related with the nested table.4) When stored in the database, the varrays retain their ordering and subscripts, while nested tables do not.Which collection type must you use? That totally depends on your wants and the size of the collection. The varray is stored as an opaque object, while a nested table is stored in a storage table with each element mapped to a row in the table. Therefore, if you want efficient queries, then use the nested tables. If you want to retrieve the whole collections as a whole, then use varrays. Though, when collections get very large, it becomes impractical to retrieve more than subsets. Therefore, varrays are better suited for the small collections
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 ROLLBACK The ROLLBACK statements end the present transaction and undo any change made during the transaction. The Rolling back is helpful for two reasons. Firstly, if yo
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ALTER TABLE bb_basketitem ADD CONSTRAINT bitems_qty_ck CHECK (quantity BEGIN INSERT INTO bb_basketitem VALUES (88,8,10.8,21,16,2,3); END; Brewbean’s wants to add a check
Use the NOCOPY Compiler Hint By default, the OUT and IN OUT parameters are passed by the value i.e. the value of an IN OUT actual parameter is copied into the corresponding fo
Parameter Default Values As the illustration below shows, you can initialize the IN parameters to the default values. In that way, you can pass various numbers of actual par
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