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Describe the definition of a transaction in SQL
Ans: The SQL transaction starts implicitly. Transactions are finished by either Commit work that commits the transaction and starts a new one Rollback work that causes the transaction to abort.
If a program ends without either of these statements after that updates are either committed or rolled back and the selection is implementation dependent.
Representing complex relationship among data A database may contain varieties of data interrelated to each other in numerous ways. A DBMS must have the capability to represent
If R1 and R2 are two union compatible relations or functions, then the result of R3 = R1 ∩R2 is the relation that contains all tuples that are in both the relations In other words,
What is Trigger? Trigger: A database trigger is procedural code which is automatically executed in response to specific events on a particular table in a database. Triggers can
Explain the two constraints, check and foreign key in SQL along with an example for each. Give the syntax. CHECK constraint - CHECK constraint specifies an expression which
What is candidate key? Candidate Key - A candidate key of an entity set is a minimal superkey, which uniquely identifies each row in the relation.
Benefits of heap files 1. This is a easy file Organisation method. 2. Insertion is somehow capable. 3. Good for bulk-loading data into a table. 4. Best if file
Column Constraints: NOT NULL, UNIQUE, CHECK, PRIMARY KEY, DEFAULT, REFERENCES, On delete Cascade : Using this key whenever a parent row is removed in a referenced
A video rental company has several branches. The data held on each branch is the branch address made up of street, city, state, and zip code, and the telephone number. Ea
When every condition appears with equality condition (=) only. c) Natural join (denoted by R*S) When two join attributes have the similar name in both relations. (Tha
The insertion of a tuple in the aim of reference does not cause any destruction. Though, insertion of a tuple in the relation in which, we has the foreign key, for instance, in ASS
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