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Explain the EXISTS and UNIQUE functions of SQL. Give an example for each?
EXISTS: The EXISTS function takes one parameter that is a SQL statement. If any records exist which match the criteria it returns true, or else it returns false. This provides you a clean, well-organized way to write a stored procedure in which does either an insert or update.
UNIQUE: If UNIQUE is particular then only unique values are used to compute the mean.
Problem: A DBMS built for Online Transaction Processing (OLTP) is usually regarded as unsuitable for data warehousing. Each system is designed with a different set of requireme
Explain data dictonary on oracle ? Data Dictionary - Data dictionaries are the system tables in which contain descriptions of the database objects and how they are structured.
If R1 and R2 are two relations or functions, then the result of R3 = R1 × R2 is the combination of tuples that are in R1 and R2. The product is associative and commutative. Degr
Nested Queries Let us see some more complex queries in this section. Sub-queries: Some of the basic concerns of sub-queries are: A sub-query is a SELECT statemen
Consider the subsequent relations for a database which keeps track of business trips of salespersons in a sales office: SALESPERSON (SSN, Name, start_year, Dept_no) TRIP (SSN, Fr
What are the problems if one were not to normalize? When do these problems surface? Ans: Database normalization, sometimes considered to as canonical synthesis, is
Define union compatibility? Explain why INTERSECTION of two relations cannot be performed if they are not union compatible? Two relations R(A1, A2,-------, An) and S(B1, B2,--
What is Message switching Message switching transmits data units which can be arbitrarily long. Packet switching has a utmost packet size, if any message longer than that, it s
a project based on normalization with first, second and third normalization. There need to be a diagram also
Secondary Indexes Let consider the student database and its clustering index and primary (only one will be applicable at a time). Now consider the state when the database is to
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