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Data Types in SQL
SQL's concept does not differ significantly from that defined in the theory book, apart from that business concerning NULL. However, the theory book equates type with the term domain used in much of the relational database literature. SQL is at odds with this equation because it uses domain for a defined subset of a given type that is not itself a type. For example, the domain WEEKDAY might be defined to consist of the values 'Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', and 'Saturday', but the declared type of a column defined on that domain is that on which the domain itself is defined, perhaps VARCHAR(9). Also, whereas a domain is defined by specifying a constraint (on some underlying type), a constraint cannot be used to specify a user-defined type.
Product-specific Packages The Oracle and different Oracle tools are supplied with the product-specific packages which help you to build the PL/SQL-based applications. For illus
Parameter and Keyword Description: select_item: This select_item is a value returned by the SELECT statement, and then assigned to the equivalent variable or field in the
Operators on Tables and Rows Row Extraction TUPLE FROM r, SQL has row subqueries. These are just like scalar subqueries except that they may specify more than one column.
Accessing Attributes: You can refer to an attribute only by its name not by its position in the object type. To access or modify the value of an attribute, you can use the dot
Varrays versus Nested Tables The Nested tables are differing from varrays in the following ways: 1) Varrays have a maximum size, while nested tables do not. 2) Varrays are
Extension and AND in SQL The theory book gives the following simple example of relational extension in Tutorial D: EXTEND IS_CALLED ADD ( FirstLetter ( Name ) AS Initial )
Referencing Records Unlike the elements in a collection, that are accessed using subscripts, the fields in a record are accessed by name. To reference an individual field, you
Using FORALL and BULK COLLECT Together You can unite the BULK COLLECT clause with the FORALL statement, in that case, the SQL engine bulk-binds column values incrementally. In
Using Subqueries A subquery is a query (typically enclosed by parentheses) that appears within another SQL data manipulation statement. If evaluated, the subquery gives a va
Order of Evaluation When you do not use the parentheses to specify the order of evaluation, the operator precedence determine the order. Now compare the expressions below: NOT
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