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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).
What is a shadow copy scheme? It is simple, but efficient, scheme known as the shadow copy schemes. It is based on making copies of the database called shadow copies that singl
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Create role named role_table that allows a user to create tables. Using role_table allow users kripa and reena to create tables. CREATE ROLE role_table; GRANT CREATE ANY TABLE
What is schema
Show a centralised schema to support the operation of the system you have chosen, including in particular: the product catalogue; the outlets and respective stocks; customer record
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List any two significant differences between a file processing system and a DBMS. File Processing System vs. DBMS Data Independence - Data independence is the capacity t
Explain group By clause in SQL? Group By clause in SQL: The GROUP BY clause can be used in a SELECT statement to collect data across multiple records and group the results thro
definition and its work
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