Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
Closest Approximation to Relational Union - SQL
Actually, just as SQL has several varieties of JOIN, it also has several varieties of UNION, none of which is equivalent to the relational operator of that name. The closest approximation to relational union is illustrated in Example.
Example: SQL's closest approximation to relational union
SELECT StudentId
FROM IS_CALLED
WHERE Name = 'Devinder'
UNION DISTINCT CORRESPONDING
FROM IS_ENROLLED_ON
WHERE CourseId = 'C1'
The key word DISTINCT is optional and implied by default (somewhat curiously so, considering that its opposite, ALL, is the default option in the SELECT clause). It specifies that no row is to appear more than once in the result. Thus, there is never a need to include DISTINCT in either of the SELECT clauses, and this would be the case even if the WHERE clause were omitted from the specification of the second operand in Example, allowing the same StudentId value to appear more than once in that operand.
The key word CORRESPONDING specifies that operand columns are to be paired by name, just as in relational union.
Keyword and Parameter Description: label_name: This is an undeclared identifier which labels an executable statement or the PL/SQL block. You can use a GOTO statement to
Multiset types - SQL An SQL multiset is what in mathematics is also known as a bag-something like a set except that the same element can appear more than once. The body of an
Biconditional - SQL The biconditional p ↔ q can be expressed in Tutorial D by p = q and the same is true of SQL. The question then arises as to whether, in SQL, p = q is equiv
Comparison Operators The Comparison operators can compare one expression to another. The outcome is always true, false, or null. Usually, you use a comparison operators in condi
This is a Customer Management project. Customer data is presented in a text file. The program will load this text data into its DB columns. The data mapping is user definable. User
Tautologies: Above given table allows us to read the truth of the connectives in the next manner. Just expect we are looking at row three. It means this says that, if there P
different lock modes used in the locking system
Character Types The Character types allow you to store alphanumeric data, represent words and text, and manipulate the character strings. CHAR You use the CHAR dataty
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
Closest Approximation to Relational Union - SQL Actually, just as SQL has several varieties of JOIN, it also has several varieties of UNION, none of which is equivalent to th
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd