SQL interview questions and answers for SQL database servers and operators

Below are the interview questions for SQL basic and intermediate level SQL Developers, Administrators, and Testers. These questions are about SQL Database servers, different types of Databases and different types of operators.

1) What is Database Server?
Database Management Systems provide Database server functionality, database server provides database services to other computer programs or computers.

2) What is MS Access?
  • MS Access was launched in 1992 by Microsoft Corporation as part of MS Office. Microsoft Access is entry-level database management software. It is not only an inexpensive but also powerful database for small-scale projects.
  • MS Access uses the Jet database engine which utilizes a specific SQL language dialect (sometimes referred to as Jet SQL).
  • MS Access comes with the professional edition of MS Office package. MS Access is user friendly database management system.

3) What is Oracle?
Oracle is a relational database management system developed by 'Oracle Corporation and launched in 1977. Oracle supports all major Operating systems includes, MS Windows. NetWare, UnixWare, OS/2 and most UNIX flavors.

4) What is MS SQL Server?
MS SQL Server is a Relational Database Management System developed by Microsoft Inc. Its primary query languages are T-SQL and ANSI SQL.

5) What is Sybase?
Sybase is a computer software company , their primary product is Sybase DBMS, which is a relational database management system based upon structured query language.

6) What is MySQL?
  • MySQL is open source Database Management System, developed by Swedish company MySQL AB.
  • MySQL Supports many different platforms including Microsoft Windows, the major Linux distributions, UNIX, and Mac OS X.
  • MySQL has free and paid versions, depending on its usage (non-commercial/commercial) and features. MySQL comes with a very fast, multi-threaded, multi-user, and robust SQL database server.

7) What is DB2?
DB2 is the short name used for DATABASE 2. It is relational database product developed by IBM. in 1983

8) What is DB/400?
It is one of the flavors of IBM DB2

9) What are the categories of operators available in SQL?
  • Arithmetic operators
  • Comparison operators
  • Logical operators

10) What are Arithmetic operators in SQL?
+ (Addition ) Adds values
- (Subtraction) Subtracts Right side value from Left side value
* (Multiplication) Multiplies values on either side of the operator
/ (Division) Divides left hand operand by right hand operand
% (Modulus) Divides left hand operand by right hand operand and returns remainder

11) What are Comparison operators in SQL?
For example x = 1, y= 2
Operator    Example
=             (x = y) is False
!=            (x != y) is True.
<>           (x <> y) is true.
>             (x > y) is False
<             (x < y) is True       
>=           (x >= y) is False
<=           (x <= y) is True
!<            (x !< y) is False
!>            (x !> y) is True.

Note: Comparison Operators return Logical Results

12) What are Logical operators in SQL? 
Operator    Description
--------        -----------
NOT           Returns TRUE if the following condition is FALSE. Returns FALSE if  it is TRUE. 
AND           Returns TRUE if both component conditions are TRUE. Returns FALSE if either is FALSE
OR            Returns TRUE if either component condition is TRUE. Returns FALSE if both are FALSE.

13) What is a Data Relationship and What are they?
Database Relationship is the connection between the tables in a database. There are 4 types of relationships, and they are:
  • One to One Relationship
  • One to Many Relationship
  • Many to One Relationship
  • Many to Many Relationship

14) What are Important Data Types in SQL?
DataType                Syntax
character                   char(x)
integer                        integer
numeric                      numeric(p,s)
decimal                       decimal(p,s)
float                             float(p)
date                             date
time                             time
character varying       varchar2(x)
bit                                bit(x)
real                             real
smallint                       smallint

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