A Database Management System (DBMS) is a program that controls creation, maintenance and use of a
database. DBMS can be termed as File Manager that manages data in a database rather than saving it in file
systems.

RDBMS stands for Relational Database Management System. RDBMS store the data into the collection of
tables, which is related by common fields between the columns of the table. It also provides relational
operators to manipulate the data stored into the tables.

SQL stands for Structured Query Language , and it is used to communicate with the Database. This is a
standard language used to perform tasks such as retrieval, updating, insertion and deletion of data from a
database. Standard SQL Commands are Select.

Database is nothing but an organized form of data for easy access, storing, retrieval and managing of data.
This is also known as structured form of data which can be accessed in many ways.

A table is a set of data that are organized in a model with Columns and Rows. Columns can be categorized as
vertical, and Rows are horizontal. A table has specified number of column called fields but can have any
number of rows which is called record.

Example:.

Table: Employee.

Field: ID, Emp Name, Date of Birth.

Data: 201456, David, 11/15/1960.

A primary key is a combination of fields which uniquely specify a row. This is a special kind of unique
key, and it has implicit NOT NULL constraint. It means, Primary key values cannot be NULL.

A Unique key constraint uniquely identified each record in the database. This provides uniqueness for the
column or set of columns. A Primary key constraint has automatic unique constraint defined on it. But not,
in the case of Unique Key. There can be many unique constraint defined per table, but only one Primary
key constraint defined per table.

A foreign key is one table which can be related to the primary key of another table. Relationship needs to
be created between two tables by referencing foreign key with the primary key of another table.

This is a keyword used to query data from more tables based on the relationship between the fields of the
tables. Keys play a major role when JOINs are used.

There are various types of join which can be used to retrieve data and it depends on the relationship
between tables.

Inner join.

Inner join return rows when there is at least one match of rows between the tables.

Right Join.

Right join return rows which are common between the tables and al rows of Right hand side table. Simply,
it returns al the rows from the right hand side table even though there are no matches in the left hand side
table.

Left Join.

Left join return rows which are common between the tables and al rows of Left hand side table. Simply, it
returns al the rows from Left hand side table even though there are no matches in the Right hand side table.

Full Join.

Full join return rows when there are matching rows in any one of the tables. This means, it returns all the
rows from the left hand side table and al the rows from the right hand side table.

Normalization is the process of minimizing redundancy and dependency by organizing fields and table of
a database. The main aim of Normalization is to add, delete or modify field that can be made in a single
table.

DeNormalization is a technique used to access the data from higher to lower normal forms of database. It
is also process of introducing redundancy into a table by incorporating data from the related tables.

The normal forms can be divided into 5 forms, and they are explained below -.

First Normal Form (1NF):.

This should remove al the duplicate columns from the table. Creation of tables for the related data and
identification of unique columns.

Second Normal Form (2NF):.

Meeting all requirements of the first normal form. Placing the subsets of data in separate tables and
Creation of relationships between the tables using primary keys.

Third Normal Form (3NF):.

This should meet al requirements of 2NF. Removing the columns which are not dependent on primary key
constraints.

Fourth Normal Form (3NF):.

Meeting all the requirements of third normal form and it should not have multi valued dependencies.

A view is a virtual table which consists of a subset of data contained in a table. Views are not virtually
present, and it takes less space to store. View can have data of one or more tables combined, and it is
depending on the relationship.

An index is performance tuning method of al owing faster retrieval of records from the table. An index
creates an entry for each value and it will be faster to retrieve data.

There are three types of indexes -.

Unique Index.

This indexing does not allow the field to have duplicate values if the column is unique indexed. Unique
index can be applied automatically when primary key is defined.

Clustered Index.

This type of index reorders the physical order of the table and search based on the key values. Each table
can have only one clustered index.

NonClustered Index.

NonClustered Index does not alter the physical order of the table and maintains logical order of data.
Each table can have 999 nonclustered indexes.

A database Cursor is a control which enables traversal over the rows or records in the table. This can be
viewed as a pointer to one row in a set of rows. Cursor is very much useful for traversing such as retrieval,
addition and removal of database records.

Database Relationship is defined as the connection between the tables in a database. There are various data
basing relationships, and they are as follows:.

One to One Relationship, One to Many Relationship, Many to One Relationship and Self-Referencing
Relationship.

A DB query is a code writ en in order to get the information back from the database. Query can be
designed in such a way that it matched with our expectation of the result set. Simply, a question to the
Database.

A sub query is a query within another query. The outer query is called as main query, and inner query is
called sub query. Sub Query is always executed first, and the result of sub query is passed on to the main
query.

There are two types of sub query – Correlated and Non-Correlated. A correlated sub query cannot be
considered as independent query, but it can refer the column in a table listed in the FROM the list of the
main query. A Non-Correlated sub query can be considered as independent query and the output of sub
query are substituted in the main query.

Stored Procedure is a function consists of many SQL statement to access the database system. Several
SQL statements are consolidated into a stored procedure and execute them whenever and wherever
required.

A DB trigger is a code or programs that automatically execute with response to some event on a table or
view in a database. Mainly, trigger helps to maintain the integrity of the database.

Example: When a new student is added to the student database, new records should be created in the
related tables like Exam, Score and Attendance tables.

DELETE command is used to remove rows from the table, and WHERE clause can be used for conditional
set of parameters. Commit and Roll back can be performed after delete statement. TRUNCATE removes al
rows from the table. Truncate operation cannot be rolled back.

Local variables are the variables which can be used or exist inside the function. They are not known to the
other functions and those variables cannot be referred or used. Variables can be created whenever that
function is called.

Global variables are the variables which can be used or exist throughout the program. Same variable
declared in global cannot be used in functions. Global variables cannot be created whenever that function
is called.

Constraint can be used to specify the limit on the data type of table. Constraint can be specified while
creating or altering the table statement. Sample of constraint are.

NOT NULL, CHECK, DEFAULT, UNIQUE, PRIMARY KEY and FOREIGN KEY.

Data Integrity defines the accuracy and consistency of data stored in a database. It can also define integrity
constraints to enforce business rules on the data when it is entered into the application or database.

Auto increment keyword allows the user to create a unique number to be generated when a new record is
inserted into the table. AUTO INCREMENT keyword can be used in Oracle and IDENTITY keyword can
be used in SQL SERVER. Mostly this keyword can be used whenever PRIMARY KEY is used.

Clustered index is used for easy retrieval of data from the database by altering the way that the records are
stored. Database sorts out rows by the column which is set to be clustered index.

A nonclustered index does not alter the way it was stored but creates a complete separate object within the
table. It point back to the original table rows after searching.

Data warehouse is a central repository of data from multiple sources of information. Those data are
consolidated, transformed and made available for the mining and online processing. Warehouse data have
a subset of data called Data Marts.

Self-join is set to be query used to compare to itself. This is used to compare values in a column with other
values in the same column in the same table. ALIAS ES can be used for the same table comparison.

Cross join defines as Cartesian product where number of rows in the first table multiplied by number of
rows in the second table. If suppose, WHERE clause is used in cross join then the query will work like an
INNER JOIN.

User defined functions are the functions writ en to use that logic whenever required. It is not necessary to
write the same logic several times. Instead, function can be called or executed whenever needed.

Following are different types of collation sensitivity -.

Case Sensitivity – A and a and B and b.

Accent Sensitivity.

Kana Sensitivity – Japanese Kana characters.

Width Sensitivity – Single byte character and double byte character.

Stored procedure can be used as a modular programming – means create once, store and cal for several
times whenever required. This supports faster execution instead of executing multiple queries. This
reduces network traffic and provides better security to the data.

Disadvantage is that it can be executed only in the Database and utilizes more memory in the database
server.

Online Transaction Processing or OLTP manages transaction based applications which can be used for
data entry and easy retrieval processing of data. This processing makes like easier on simplicity and
efficiency. It is faster, more accurate results and expenses with respect to OTLP.

SQL clause is defined to limit the result set by providing condition to the query. This usual y filters some
rows from the whole set of records.

Example – Query that has WHERE condition

Query that has HAVING condition.

A stored procedure which cal s by itself until it reaches some boundary condition. This recursive function
or procedure helps programmers to use the same set of code any number of times.

UNION operator is used to combine the results of two tables, and it eliminates duplicate rows from the
tables.

MINUS operator is used to return rows from the first query but not from the second query. Matching
records of first and second query and other rows from the first query will be displayed as a result set.

INTERSECT operator is used to return rows returned by both the queries.

ALIAS name can be given to a table or column. This alias name can be referred in WHERE clause to
identify the table or column.

Example-.

1 Select st.StudentID, Ex. Result from student st, Exam as Ex where

Here, st refers to alias name for student table and Ex refers to alias name for exam table.

TRUNCATE removes al the rows from the table, and it cannot be rolled back. DROP command removes a
table from the database and operation cannot be rolled back.

Aggregate functions are used to evaluate mathematical calculation and return single values. This can be
calculated from the columns in a table. Scalar functions return a single value based on the input value.

Example -.

Aggregate – max(), count – Calculated with respect to numeric.

Scalar – UCASE(), NOW() – Calculated with respect to strings.

Example will be -.

1 Select * into student copy from student where 1=2;

Here, we are copying student table to another table with the same structure with no rows copied.

Common records result set can be achieved by -.

1 Select studentID from student. <strong>INTERSECT </strong>

Records can be fetched for both Odd and Even row numbers -.

To display even numbers-.

1 Select studentId from (Select row no, studentId fromstudent)

To display odd numbers-.

1 Select studentId from (Select row no, studentId from student)

from (Select row no, studentId from student) where mod(rowno,2)=1.[/sql]

Select unique records from a table by using DISTINCT keyword.

1 Select DISTINCT StudentID,Student Name from Student.

There are many ways to fetch first 5 characters of the string -.

1 Select SUBSTRING(StudentName,1,5) as student name from student;

1 Select RIGHT(Studentname,5) as student name from student;

LIKE operator is used for pattern matching, and it can be used as -.

1. Matches zero or more characters.

2._(Underscore) – Matching exactly one character.

Example -.

1 Select * from Student where student name like  ‘a%’ ;

1 Select * from Student where student name like ‘ami_’;

MySQL is an open source DBMS which is built, supported and distributed by MySQL AB (now acquired
by Oracle)

MySQL database software is a client or server system which includes

Multithreaded SQL server supporting various client programs and libraries

Different backend

Wide range of application programming interfaces and

Administrative tools.

MySQL database server is reliable, fast and very easy to use. This software can be downloaded as
freeware and can be downloaded from the internet.

HEAP tables are present in memory and they are used for high speed storage on temporary basis.

• BLOB or TEXT fields are not al owed

• Only comparison operators can be used =, <,>, = >,=<

• AUTO_INCREMENT is not supported by HEAP tables

• Indexes should be NOT NULL

The default port for MySQL server is 3306.

• MySQL is open source software which is available at any time and has no cost involved.
• MySQL is portable
• GUI with command prompt.
• Administration is supported using MySQL Query Browser

Following are differences for FLOAT and DOUBLE:

• Floating point numbers are stored in FLOAT with eight place accuracy and it has four bytes.

• Floating point numbers are stored in DOUBLE with accuracy of 18 places and it has eight bytes.

CHAR_LENGTH is character count whereas the LENGTH is byte count. The numbers are same for Latin
characters but they are different for Unicode and other encodings.

ENUMs and SETs are used to represent powers of two because of storage optimizations.

ENUM is a string object used to specify set of predefined values and that can be used during table
creation.

REGEXP is a pattern match in which matches pattern anywhere in the search value.

Following are the differences between CHAR and VARCHAR:

CHAR and VARCHAR types differ in storage and retrieval

CHAR column length is fixed to the length that is declared while creating table. The length value ranges
from 1 and 255

When CHAR values are stored then they are right padded using spaces to specific length.

The string types are:

• SET
• BLOB
• ENUM
• CHAR
• TEXT
• VARCHAR

1SELECT VERSION ()?

is used to get the current version of MySQL.

Storage engines are called table types and data is stored in files using various techniques.

Technique involves:

• Storage mechanism
• Locking levels
• Indexing
• Capabilities and functions.

Following are the drivers available in MySQL:

• PHP Driver
• JDBC Driver
• JOBSMATE.COM
• ODBC Driver
• C WRAPPER
• PYTHON Driver
• PERL Driver
• RUBY Driver
• CAP11PHP Driver
• Ado.net5.mxj

TIMESTAMP column is updated with Zero when the table is created. UPDATE
CURRENT_TIMESTAMP modifier updates the timestamp field to current time whenever there is a
change in other fields of the table.

Every row of a table is identified uniquely by primary key. There is only one primary key for a table.
Primary Key is also a candidate key. By common convention, candidate key can be designated as primary
and which can be used for any foreign key references.

We can login through this command

# [mysql dir]/bin/mysql -h hostname -u <UserName> -p <password>

It compress the MyISAM tables, which reduces their disk or memory usage.

Maximum size of Heal table can be controlled by MySQL config variable cal end

max_heap_table_size.

In MyISAM static al the fields will have fixed width. The Dynamic MyISAM table will have fields like
TEXT, BLOB, etc. to accommodate the data types with various lengths. MyISAM Static would be easier
to restore in case of corruption.

Federated tables which allow access to the tables located on other databases on other servers.

Timestamp field gets the current timestamp whenever the row gets altered.

It stops incrementing. Any further inserts are going to produce an error, since the key has been used
already.

LAST_INSERT_IDCareerarm.com return the last value assigned by Auto_increment and it is not required
to specify the table name

Indexes are defined for the table by:
SHOW INDEX FROM <tablename>?

% corresponds to 0 or more characters, _ is exactly one character in the LIKE statement.

UNIX_TIMESTAMP is the command which converts from MySQL timestamp to Unix timestamp

FROM_UNIXTIME is the command which converts from Unix timestamp to MySQL timestamp.

The = , <>, <=, <, >=, >,<<,>>, <=>, AND, OR, or LIKE operators are used in column comparisons in
SELECT statements.

Number of rows can be obtained by

1 SELECT COUNT (user_id) FROM users?

No.

1) SELECT VERSION(), CURRENT_DATE?

2 )Select version(), current_date?

3 )select version(), current DATE?

All these examples are same. It is not case sensitive.

LIKE and REGEXP operators are used to express with ^ and %.

1) SELECT * FROM employee WHERE emp_name REGEXP "^b"?

2) SELECT * FROM employee WHERE emp_name LIKE "%b"?

A BLOB is a binary large object that can hold a variable amount of data. There are four types of BLOB –

• TINYBLOB
• BLOB
• MEDIUMBLOB and
• LONGBLOB

They all differ only in the maximum length of the values they can hold.

The = , <>, <=, <, >=, >,<<,>>, <=>, AND, OR, or LIKE operators are used in column comparisons in
SELECT statements.

Number of rows can be obtained by

1 SELECT COUNT (user_id) FROM users?

No.

1) SELECT VERSION(), CURRENT_DATE?

2 )Select version(), current_date?

3 )select version(), current_DATE?

All these examples are same. It is not case sensitive.

A TEXT is a case-insensitive BLOB. The four TEXT types

TINYTEXT

TEXT

MEDIUMTEXT and

LONGTEXT

They all correspond to the four BLOB types and have the same maximum lengths and storage requirements.

The only difference between BLOB and TEXT types is that sorting and comparison is performed
incase-sensitive for BLOB values and case-insensitive for TEXT values.

Following are the differences between mysql_fetch_array and mysql_fetch_object:

mysql_fetch_array() -Returns a result row as an associated array or a regular array from database.

mysql_fetch_object - Returns a result row as object from database.

Following commands are used to run in batch mode:

1) mysql?

2) mysql mysql.out.

Each MyISAM table is stored on disk in three formats:

• The ‘.frm’ file stores the table definition
• The data file has a ‘.MYD’ (MYData) extension
• The index file has a ‘.MYI’ (MYIndex) extension.

Total 5 types of tables are present:

• MyISAM
• Heap
• Merge
• INNO DB
• ISAM

MyISAM is the default storage engine as of MySQL

ISAM is abbreviated as Indexed Sequential Access Method. It was developed by IBM to store and retrieve
data on secondary storage systems like tapes.

lnnoDB is a transaction safe storage engine developed by Innobase Oy which is a Oracle Corporation now.

DISTINCT is converted to a GROUP BY on al columns and it wil be combined with ORDER BY clause.

1 SELECT DISTINCT t1.a FROM t1,t2 where t1.a=t2.a?

If you want to enter characters as HEX numbers, you can enter HEX numbers with single quotes and a
prefix of (X), or just prefix HEX numbers with (Ox).

A HEX number string will be automatically converted into a character string, if the expression context is a
string.

In MySql, top 50 rows are displayed by using this following query:

1 ) SELECT * FROM

2 ) LIMIT 0,50?

Maximum of 16 indexed columns can be created for any standard table.

NOW () command is used to show current year,month,date with hours, minutes and seconds.
CURRENT_DATE() shows current year, month and date only.

Following objects are created using CREATE statement:

• DATABASE
• EVENT
• FUNCTION
• INDEX
• PROCEDURE
• TABLE
• TRIGGER
• USER
• VIEW

SIX triggers are al owed in MySql table. They are as follows:

• BEFORE INSERT
• AFTER INSERT
• BEFORE UPDATE
• AFTER UPDATE
• BEFORE DELETE and
• AFTER DELETE.

Following are Non-Standard string types:

• TINYTEXT
• TEXT
• MEDIUMTEXT
• LONGTEXT.

CONCAT(A, B) – Concatenates two string values to create a single string output. Often used to combine
two or more fields into one single field.
FORMAT(X, D) – Formats the number X to D significant digits.

CURRDATE(), CURRTIME() – Returns the current date or time.

NOW() – Returns the current date and time as one value.

MONTH(), DAY(), YEAR(), WEEK(), WEEKDAY() – Extracts the given data from a date value.

HOUR(), MINUTE(), SECOND() – Extracts the given data from a time value.

DATEDIFF(A, B) – Determines the difference between two dates and it is commonly used to calculate
age

SUBTIMES(A, B) – Determines the difference between two times.

FROMDAYS(INT) – Converts an integer number of days into a date value.

An ACL (Access Control List) is a list of permissions that is associated with an object. This list is the basis
for MySQL server’s security model and it helps in troubleshooting problems like users not being able to
connect.

MySQL keeps the ACLs (also called grant tables) cached in memory. When a user tries to authenticate or
run a command, MySQL checks the authentication information and permissions against the ACLs, in a
predetermined order.