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Aggregate AssignmentThe %ROWTYPE declaration cannot include an initialization clause. Though, there are two ways to assign values to all fields in a record at once. At First, the PL/SQL allows the aggregate assignment between the whole records if their declarations refer to the similar table or cursor. For illustration, the assignment below is legal:DECLAREdept_rec1 dept%ROWTYPE;dept_rec2 dept%ROWTYPE;CURSOR c1 IS SELECT deptno, dname, loc FROM dept;dept_rec3 c1%ROWTYPE;BEGIN...dept_rec1 := dept_rec2;However, because dept_rec2 is based on a table and dept_rec3 is based on acursor, the following assignment is illegal:dept_rec2 := dept_rec3; -- illegalSecondly, you can assign a list of column values to a record by using the SELECT or FETCH statement, as the illustration below shows. The column names should appear in the order in which they are defined by the CREATE TABLE or CREATE VIEW statement.DECLAREdept_rec dept%ROWTYPE;...BEGINSELECT deptno, dname, loc INTO dept_rec FROM deptWHERE deptno = 30;
Assignment Source Not a Literal - Variable Syntax: SET SN = SID (SUBSTRING (SN.C FROM 1 FOR 1)||'5');
Example of COALESCE operator Example: Give the total of marks for each exam (simplified solution) SELECT CourseId, COALESCE ((SELECT SUM (Mark) FROM EXAM_MARK AS EM
Using LOCK TABLE You use the LOCK TABLE statement to lock the whole database tables in the specified lock mode so that you can share or deny the access to them. For illustrati
Initializing and Referencing Collections Until you initialize a collection, a nested table or varray is automatically null (i.e. the collection itself is null, not its elements)
Information Hiding With the information hiding, you see only the details that are significant at a given level of algorithm and data structure design. The Information hiding
Using FIRST and LAST FIRST and LAST return the first and last (minimum and maximum) index numbers in a collection. When the collection is empty, the FIRST and LAST return NULL
Explicitly specifying the join condition - SQL SELECT * FROM IS_CALLED JOIN IS_ENROLLED_ON ON ( IS_CALLED.StudentId = IS_ENROLLED_ON.StudentId ) Now, the key word JO
Important Distinctions The list of important distinctions are given below: Value versus variable Syntax versus semantics Variable versus variable reference
Explicit Cursors The set of rows returned by the query can include zero, one, or multiple rows, depending on how many rows meet your search criteria. Whenever a query returns
LEVEL You use the LEVEL with the SELECT CONNECT BY statement to categorize rows from a database table into a tree structure. The LEVEL returns the level number of a node in a
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