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Update Operations and Dealing with Constraint Violations
There are three basic operations to be executes on relations:
The INSERT Operation:
The insert operation permits us to insert a new tuple in a relation. When we try to insert a new record, then any of the following four types of constraints can be violated:
• Entity Integrity constraint: If the primary key attribute value of new tuple t is given as null.
Mappings between Levels and Data Independence The 3 levels of abstraction in the database do not exist separately of each other. There must be some correspondence, or mapping
let us consider a table having 2200 records and the fixed size of the table to be considered as 25.then how many numbers of table is requredto perform horizontal fragmentation
Define check point and its impact on data base recovery. Ans: There could be hundreds of transactions handled per minute, in a large on-line database system.
Define cardinality and participation constraints on a relationship type, completeness constraint on generalization. Ans: Cardinality defines the number of entities to wh
Define single valued and multivalued attributes. Single valued attributes: attributes with a single value for a particular entity are known as single valued attributes. M
What is the difference between WHERE and HAVING clauses?. Predicates in the WHERE clause applies to every tuple while the predicate in the HAVING clause applies to groups.
Consider the relation schemas as follows. works (person name, company name, salary); lives (person name, street, city); located in(company name, city); managers (person name
i am not clear with the climetic condition of the north indian plain. can u plz explain it for me
3NF Normal Form A relation schema R is in 3NF if it is in 2NF and for each FD X A either of the following is true X is a Super-key of R. A is a prime attribute of R
What are called index-sequential files? The files that are ordered sequentially with a primary index on the search key are known as index-sequential files
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