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Assigning and Comparing CollectionsOne collection can be assigned to other by an SELECT, INSERT, UPDATE, or FETCH statement, an assignment statement, or by a subprogram call. As the illustration shown below, the collections should have the same datatype. Having the similar element type is not enough.DECLARETYPE Clientele IS VARRAY(100) OF Customer;TYPE Vips IS VARRAY(100) OF Customer;group1 Clientele := Clientele(...);group2 Clientele := Clientele(...);group3 Vips := Vips(...);BEGINgroup2 := group1;group3 := group2; -- illegal; Various datatypes becomes automatically null (and should be reinitialized). Now consider the illustration as shown below: DECLARETYPE Clientele IS TABLE OF Customer;group1 Clientele := Clientele(...); -- initializedgroup2 Clientele; -- atomically nullBEGINIF group1 IS NULL THEN ... -- condition yields FALSEgroup1 := group2;IF group1 IS NULL THEN ... -- condition yields TRUE...END;Similarly, if you assign the non-value NULL to a collection, the collection becomes automatically null.Assigning Collection ElementsYou can assign the value of an expression to the specific element in a collection by using the syntaxcollection_name(subscript) := expression;Where the expression yields a value of the type specified for elements in the collection type definition. If the subscript is null or not convertible to an integer, the PL/SQL raises the predefined exception VALUE_ERROR. If the collection is automatically null, then the PL/SQL raises COLLECTION_IS_NULL. Some of the examples are shown below:DECLARETYPE NumList IS TABLE OF INTEGER;nums NumList := NumList(10,20,30);ints NumList;...BEGIN...nums(1) := TRUNC(high/low);nums(3) := nums(1);nums(2) := ASCII(’B’);/* Assume execution continues despite the raised exception. */nums(’A’) := 40; -- raises VALUE_ERRORints(1) := 15; -- raises COLLECTION_IS_NULLEND;Comparing Whole CollectionsThe Nested tables and varrays can be automatically null; therefore they can be tested for the nullity, as the example below shows:DECLARETYPE Staff IS TABLE OF Employee;members Staff;BEGIN...IF members IS NULL THEN ... -- condition yields TRUE;END;Though, the collections cannot be compared for equality or inequality. For illustration, the IF condition below is illegal as shown:DECLARETYPE Clientele IS TABLE OF Customer;group1 Clientele := Clientele(...);group2 Clientele := Clientele(...);BEGIN...IF group1 = group2 THEN -- causes compilation error...END IF;END;This restriction also applies to implicit the comparisons. For illustration, the collections cannot appear in an ORDER BY, GROUP BY, or DISTINCT list.
CLOSE Statement The CLOSE statement allows the resources held by a cursor variable or open cursor to be reused. No more rows can be fetched from the cursor variable or closed
Data Types in SQL - Integer INTEGER or synonymously INT, for integers within a certain range. SQL additionally has types SMALLINT and BIGINT for certain ranges of integers. T
Updating Variables For assignment, SQL uses the key word SET, as in SET X = X + 1 (read as "set X equal to X+1") rather than X: = X + 1 as found in many computer languages.
Creating and Destroying Base Tables: Example shows an SQL command to create the base table counterpart of the ENROLMENT variable Example Creating a base table. CREATE T
Relational Operators and Logical Operators It prepares the ground for subsequent sections in which each specific relational operator is paired with its logical counterpart, su
a. Create a table odetails_new. It has all the attributes of odetails and an additional column called cost, whose values are the product of the quantity and price of the part bein
The accuracy of product table data is critical and the Brwebean's. owner wants to have an audit file that contains information regarding all DML activity on the BB_PRODUCT table. T
Many of the reports generated from the system calculate the total dollars in a shopper''s purchases. Follow these steps to create a function named TOT_PURCH_SF that accepts a shopp
Transaction context As the figure shows, the major transaction shares its context with the nested transactions, but not with the autonomous transactions. Similarly, If one aut
TTITLE and BTITLE are commands in Pl-SQL to control report headings and footers. This Ttitle & Btitle are mainly used on creating SQL*PLUS report. Ttitle is used for toptitle headi
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