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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 must always be true for every row in the table. It can't refer to values within other rows.Syntax:ALTER TABLE ADD CONSTRAINT CHECK();
FOREIGN KEY constraint - A foreign key is a combination of columns along with values based on the primary key values from another table. A foreign key constraint, also called as referential integrity constraint, specifies in which the values of the foreign key correspond to actual values of the primary or unique key in other table. One can refer to a primary or unique key in the similar table also.
Syntax: ALTER TABLE ADD CONSTRAINT FOREIGN KEY()REFERENCES () ON {DELETE | UPDATE}CASCADE;
Two Phase Locking (2PL) The two-phase locking protocol having of two phases: Phase 1 : The lock acquisition phase : If a transaction T needs to read an object, it wants to
With the help of an example display how records can be deleted and updated in QBE. (i) Increase Pay_Rate of employees along with the skill of ‘cook' by 10%. (ii) Delete employee
domain
what is union compatable?
Explain the systems development life cycle. This is the traditional method to develop, maintain, and replace information systems that contains the project identification and se
Normalize the following table upto and including the 3NF. Submit a 1 page printout of only the final set of normalized tables in Data Architect. Just use Data Architect to do the t
Explain data independence ? Data independence is the capacity to modify the schema at one stage of a database system without having to change the schema at the further level.
1) Information about a bank is about customers and their account. Customer has a name, address which consists of house number, area and city, and one or more phone numbers. Ac
Is it mandatory to declare all the tables in Report by the key word tables for all the tables that exist in the structure of LDB, and are being explained in the Database part of LD
differences between a classified catalog and a dictionary catalog
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