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Example of Alternative formulation as a table constraint
Example: Alternative formulation as a table constraint
ALTER TABLE EXAM_MARK
ADD CONSTRAINT Must_be_enrolled_to_take_exam_alternative2
CHECK (EXISTS (SELECT StudentId, CourseId
FROM IS_ENROLLED_ON
WHERE StudentId = EXAM_MARK.StudentId
AND CourseId = EXAM_MARK.CourseId)
) ;
In Example, note the use of the table name, EXAM_MARK, as a range variable to qualify references to columns of that table. As always, the condition given as the operand of CHECK is one that would be legal as a WHERE condition following a FROM clause specifying just the table to which the constraint applies (viz., FROM EXAM_MARK in the case at hand).
Wrapping and unwrapping in SQL Operators WRAP and UNWRAP in connection with attributes whose declared types are tuple types. Example shows how extension and projection can be
Project Description: We organize an online system called ACPAS we have created a project called EVO that can be use by our customers to integrate their web sites with the Acpas
Manipulating Objects: You can use an object type in the CREATE TABLE statement to indicate the datatype of a column. When the table is created once, you can use the SQL statem
GOTO Statement The GOTO statement branches to a label unconditionally. The label must be exclusive within its scope and should precede an executable statement or a PL/SQL block.
Cursor Attributes The Cursors and cursor variables have 4 attributes which give you helpful information about the execution of a data manipulation statement. Syntax:
Example of ADD CONSTRAINT in SQL Example: Alternative formulation for MAX_ENROLMENTS ALTER TABLE IS_ENROLLED_ON ADD CONSTRAINT MAX_ENROLMENTS CHECK ((SELECT COUNT (*)
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 the Collection Methods The collection methods below help to generalize the code and make collections easier to use and also make your applications easier to maintain:
UNION ALL - SQL Further varieties of UNION arise when we replace the key word DISTINCT by ALL in any of the foregoing examples, as in Example. ALL specifies that if row r appe
DBMS_OUTPUT: The Package DBMS_OUTPUT enables you to display output from the PL/SQL subprograms and blocks, that makes it easier to test and debug them. The procedure put_ line
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