The CASE statement is popularly known as CASE Expression, allows the user to execute a part of SQL statement conditionally. In SQL, CASE statement is used for storing the procedure or formula of a particular column. The CASE expression can be classified into two types namely: Simple CASE Statement Searched CASE Statement Basic Syntax for […]
Concurrent Update Problem
Concurrent update problem in a database can be defined as the occur when multiple sessions are allowed to update their data present in a single database. Concurrent update problem may lead to data integrity loss and data corruption. Read: More Interview Questions Example for Concurrent Update Problem Imagine that we have an application which manages […]
What is Natural Key?
Natural key can be defined as an identifier of row which is composed of data. The data present in the database will describe according to its attributes. The row identifier in a database is the focal point of clustered and nonclustered indexes. What is Cost Based Optimizer? Why it is called as Natural key? Consider […]
What is Meant by Inner and Outer Joins?
Joins in SQL are used to return rows by combining and comparing different tables present in a database. Joins are classified into two types: Inner Join Outer Join Inner Join Inner Join is used to find the similarities between two tables present in a database. Inner Join searches for overlapping data in a table. If […]
What is Meant by Database Index?
Database indexes in SQL, allows the developer to quickly retrieve the data from a database. The searching process in a database can be accelerated using database indexes. A database index is a copy of key values stored in a table. If database index is not used, then every query will scan the entire table to […]
What is Lock Escalation?
Lock escalation is the process of increasing the levels of database locks. Lock escalation is supported by popular databases like SQL Server, SyBase and DB2. In DB2, the parameters like ALTER TABLESPACE and LOCKMAX of CREATE TABLESPACE are used to control lock escalation. Read: SQL Database Deadlock What is the purpose of lock escalation? The […]
What is Database Transaction?
Database transaction can be defined as the separate actions which are in either processed or yet to be processed state. All or Nothing is the defining feature of a database transaction. Each and every database transaction will contain several SQL statements. The common database transaction scenario can be noted using the acronym ACID. How to […]