SQL stands for Structured Query Language. It is used in databases to manipulate and retrieve data from database. It mainly used in relational databases.
When you attending any software
interview, you will get the questions from SQL. Because it is the basic language
and easy one too.
Let us discuss the interview
questions....
Before starting the SQL, you
must know about database and RDBMS.
A database is a collection of
data stored in a system in an organized way. Using SQL, you can retrieve
the data.
RDBMS (Relational Database
Management system)is a software which is used to create, retrieve ,update and
manage the database. The data is stored in the form of tables.
Next, SQL interview questions
are given below….
1.What is
SQL?
SQL is Structured Query Language which is
used to define ,retrieve and manipulate
data from databases.
2.Name some
SQL servers.
Some examples are
MySQL,PostgreSQL,Oracle,Microsoft SQL server, SQLite.
3.What is a
tuple?
A tuple is a set of values of an individual
record. For example, In Class A table, a
record of a student is called a tuple.
Class A
|
Student
name |
Roll no |
Rank |
|
Ajay |
1 |
5 |
|
Baby |
2 |
10 |
|
Charlie |
3 |
6 |
4.What is
DDL?
DDL stands for Data Definition Language.
It is used to define things in SQL.
Eg:
CREATE,ALTER,DROP,TRUNCATE,COMMENT,RENAME
5.What is DML?
DML is Data Manipulation Language which
is used to manipulate data. it is
used to store,
modify, retrieve, delete and update data in a database. It has
following SQL commands
SELECT,INSERT,UPDATE,DELETE,MERGE,CALL,EXPLAIN
PLAN,
LOCK TABLE.
6.What is DCL?
DCL is Data Control Language which is used
to grant permissions and controls the
database. It includes GRANT ,REVOKE commands.
7.What is
TCL?
TCL is Transaction Control Language. It is used in transactions of a database. It includes
COMMIT,ROLLBACK,SAVEPOINT and SET TRANSACTION commands.
8. How to create table in SQL?
To create table in SQL, follow the given syntax.
Create table table_name(column1 datatype, column2 datatype,.....,column n datatype);
Eg: Create table student(stu_name varchar(20), stu_id INT PRIMARY KEY,stu_class
varchar(10));
9.How to
insert data in to a table in SQL?
To insert a data, the syntax is given below. INSERT INTO
table_name(column1,column2,...) VALUES(VALUE1,VALUE2,....)
Eg: INSERT INTO student(stu_name,stu_id,stu_class) values(‘ajay’,1,’commerce’);
This command is used to display the
records in the database. It has the following
syntax
SELECT * FROM table_name;
SELECT Column_name(s) FROM table_name;
Eg: SELECT * FROM student;
It displays the entire records from table student.
These are some basic interview questions of SQL. Part 2 contains the advance concepts of SQL.
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