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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.
Object Oriented model :An object has values stored in instance variables within the object. An object also has bodies of code that execute on the object. These bodies of code are
What Count function return in SQL? Count function within SQL returns the number of values. (Count function counts all the not null values in the exact column. If we need to cou
List the string operations supported by SQL? 1) Pattern matching Operation 2) Concatenation 3) Extracting character strings 4) Converting among uppercase and lower cas
What is System R? What are its two major subsystems? System R was intended and developed over a period of 1974-79 at IBM San Jose Research Center. It is a prototype and its pur
#questiontypes of keys examples..
An instance of relational schema R (A, B, C) has distinct values of A including NULL values. then A is a candidate key or not? If relational schema R (A, B, C) has distinct val
What is Trigger? A trigger is a SQL procedure that initiates an action when an event (INSERT, DELETE or UPDATE) occurs. Triggers are kept in and managed by the DBMS. Triggers a
Multi-Key File Organisation In this part, we will introduce two basic file Organisation schemes that permit records to be accessed by more than one key field, therefore, allowi
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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
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