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What is the difference between a key and a superkey?
Key - A key a single attribute or a combination of two or more attributes of an entity set which is used to identify one or more examples (rows) of the set (table). It is a minimal combination of attributes.
Super Key - A super key is a set of one or more attributes in which, taken collectively, permits us to identify uniquely a tuple within the relation.
Data Replication "If a relation R has its copies kept at two or more sites, then it is considered replicated". But why do we replicate a relation? There are several advan
employee(empid,empname,dept,telno,mobno, add,sssno,tinno,WEdates,WEcomp,WEadd,WEpos,WEres) this is a employee record which is need to be normalize.the WE means work experience
Have a look around the site, and at some of the sites they have featured. These are all examples of bad design, and also offer an explanation about why they fall into this category
Example- Search the salary of employees who are not 'ANALYST' but get a salary below than or equal to any people employed as 'ANALYST'. SELECT EMPNO, ENAME, JOB, SAL FROMEMP
Describe multi key files
The data of a view is not physically stored, but derived from one or more tables. True the data of a view is not physically stored
Increases efficiency : Data is stored close to most often used site, therefore retrieval would be faster. Also, data that is not required by local applications is not stored, there
Given the following set of functional dependencies {cf?bg, g?d, cdg?f, b?de, d?c} defined on R(b,c,d,e,f,g) a.Find a non-redundant cover. b.Find a canonical cover.
What is Relational calculus? Relational calculus is a Non- Procedural language.
Write short notes on domain relational calculus The domain relational calculus uses domain variables that take on values from an attribute domain rather than values for whole t
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