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Explain several types of constraints that can be specified using CREATE TABLE command. Explain CASCADE and RESTRICT clauses of DROP SCHEMA command?Constraint DescriptionPRIMARY KEY Determines that column(s) uniquely identifies each record. The primary key cannot be NULL, and the data value(s) must be unique.
FOREIGN KEY In a one-to-many relationship, the constraint is added to the "many" table. The constraint ensures which if a value is entered into a specified column, it must already exist in the "one" table, or the record is not added.
UNIQUE Ensures that all data values stored in a specified column are unique.The UNIQUE constraint differs from the PRIMARY KEY constraint in which it permits NULL values.CHECK Ensures in which a specified condition is true before the data value is added to a table. For example, an order's ship date cannot be previous than its order date.
NOT NULL Ensures in which a specified column cannon contain a NULL value. The NOT NULL constraint can just be created along with the column-level approach to table creation.
Prevents the DROP from taking place if any dependent objects exists (RESTRICT) or causes all dependent objects do also be dropped (CASCADE).
You are required to implement integrity constraints within the database to enforce the following requirements: For Projects: Start date must be supplied. Start date cannot be i
Suppose an instruction takes 1 nanosecond to execute (on average), a page fault takes 20 microseconds of processor time, and it takes 300 microseconds of disk time to read or write
Explain nested relations? Nested relations The assumption of INF is a natural one in the bank examples we have considered. However, not all applications are best modelled
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Describe different steps of the object-oriented design process. The broad steps of the object-oriented design process are: a. Define context and modes of use of the system
File Organisation And Its Types Just as arrays, trees, lists and other data structures are used to execute data Organisation in main memory, a number of planning's are used to
For every multivalued attribute 'A', we make a new relation R that contains an attribute corresponding to plus the primary key attribute k of the relation that shows the entity typ
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What is the difference between a HAVING CLAUSE and a WHERE CLAUSE? HAVING CLAUSE - HAVING CLAUSE is used only with SELECT statement. - It is normally used in a GROUP BY
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