DBMS - Quick reference - 3

11. What is a join in the SQL?
A SQL Join is a form of generating a meaningful data by combining multiple tables relate to each other using a 'Key'. A JOIN is a means for combining fields from two tables by using values common to each.

12. What integrity rules exist in the DBMS?
The two types of  integrity rules are referential integrity rules and entity integrity rules. Referential integrity rules dictate that a database does not contain orphan foreign key values. A primary key value cannot be modified if the value is used as a foreign key in a child table. Entity integrity dictates that the primary key value cannot be Null.

13. Explain the concept of ACID properties in DBMS?
In DBMS, ACID (atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee validity even in the event of errors, power failures, etc. In the context of databases, a sequence of database operations that satisfies the ACID properties is called a transaction.

14. Explain the purpose of normalization in DBMS ?
Database normalization is a process used to organize a database into tables and columns.  The main idea with this is that a table should be about a specific topic. This will prevent the same data from being stored in many places. Prevent updates made to some data and not others.This will ensure queries are more efficient.

15. How is the pattern matching done in the SQL?
You can use two wildcards often used in conjunction with the LIKE operator:
% : The percent sign represents zero, one, or multiple characters.
_ : The underscore represents a single character.
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