How To Create A Database & MySQL DataTypes

Creation of a Database is the first step of practicing Database operations.

You can create database in two ways

1)    By executing a simple SQL query

2)    By using forward engineering in MySQL Workbench

As SQL beginner , let's look into the query method first.

 

 

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CREATE DATABASE is the SQL command for creating a database. 

 

Imagine you need to create a database with name "movies". You can do it by executing following SQL command.

 

CREATE DATABASE movies; 

Note: you can also use the command CREATE SCHEMA instead of CREATE DATABASE

Now let's improve our SQL query adding more parameters and specifications.

IF NOT EXISTS

 A single MySQL server could have multiple databases. If you are not the only one accessing the same MySQL server or if you have to deal with multiple databases there is a probability of attempting to create a new database with name of an existing database .  IF NOT EXISTS let you to instruct MySQL server to check the existence of a database with a similar name prior to creating database.

When IF NOT EXISTS is used database is created only if given name does not conflict with an existing database's name. Without the use of IF NOT EXISTS MySQL throws an error.

CREATE DATABASEIF NOT EXISTS movies;

Collation and Character Set

Collationis set of rules used in comparison. Many people use MySQL to store data other than English. Data is stored in MySQL using a specific character set. The character set can be defined at different levels viz, server , database , table and columns.

You need to select the rules of collation which in turn depend on the character set chosen.

For instance, the Latine1 character set uses the latin1_swedish_ci collation which is the Swedish case insensitive order.

CREATE DATABASE IF NOT EXISTS movies CHARACTER SET latin1 COLLATE latin1_swedish_ci

The best practice while using local languages like Arabic , Chinese etc is to select Unicode (utf-8) character set which has several collations or just stick to default collation utf8-general-ci.

You can find the list of all collations and character sets here here

You can see list of existing databases by running following SQL command.

SHOW DATABASES

Creating Tables in MySQL


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Tables can be created using CREATE TABLE statement and it actually has the following syntax.

CREATE  TABLE [IF NOT EXISTS] `TableName` (`fieldname` dataType [optional parameters]) ENGINE = storage Engine; 

HERE

  • "CREATE TABLE" is the one responsible for the creation of the table in the database.
  • "[IF NOT EXISTS]" is optional and only create the table if no matching table name is found.
  • "`fieldName`" is the name of the field and "data Type" defines the nature of the data to be stored in the field.
  • "[optional parameters]" additional information about a field such as "  AUTO_INCREMENT" , NOT NULL etc

    Example:-


    CREATE  TABLE IF NOT EXISTS `MyFlixDB`.`Members` (
      `membership_number` INT  AUTOINCREMENT ,
      `full_names` VARCHAR(150) NOT NULL ,
      `gender` VARCHAR(6) ,
      `date_of_birth` DATE ,
      `physical_address` VARCHAR(255) ,
      `postal_address` VARCHAR(255) ,
      `contact_number` VARCHAR(75) ,
      `email` VARCHAR(255) ,
      PRIMARY KEY (`membership_number`) )
    ENGINE = InnoDB;

Now let's see what the MySQL's data types are. You can use any of them depending on your need. You should always try to not to underestimate or overestimate potential range of data when creating a database.

Data types define the nature of the data that can be stored in a particular column of a table

MySQL has 3 main categories of data types namely

  1.   Numeric,
  2.   Text
  3.   Date/time.

Numeric Data types

Numeric data types are used to store numeric values. It is very important to make sure range of your data is between lower and upper boundaries of numeric data types.

TINYINT( )

-128 to 127 normal
0 to 255 UNSIGNED.

SMALLINT( )

-32768 to 32767 normal
0 to 65535 UNSIGNED.

MEDIUMINT( )

-8388608 to 8388607 normal
0 to 16777215 UNSIGNED.

INT( )

-2147483648 to 2147483647 normal
0 to 4294967295 UNSIGNED.

BIGINT( )

-9223372036854775808 to 9223372036854775807 normal
0 to 18446744073709551615 UNSIGNED.

FLOAT

A small approximate number with a floating decimal point.

DOUBLE( , )

A large number with a floating decimal point.

DECIMAL( , )

A DOUBLE stored as a string , allowing for a fixed decimal point. Choice for storing currency values.

Text Data Types

As data type category name implies these are used to store text values. Always make sure you length of your textual data do not exceed maximum lengths.

CHAR( )

A fixed section from 0 to 255 characters long.

VARCHAR( )

A variable section from 0 to 255 characters long.

TINYTEXT

A string with a maximum length of 255 characters.

TEXT

A string with a maximum length of 65535 characters.

BLOB

A string with a maximum length of 65535 characters.

MEDIUMTEXT

A string with a maximum length of 16777215 characters.

MEDIUMBLOB

A string with a maximum length of 16777215 characters.

LONGTEXT

A string with a maximum length of 4294967295 characters.

LONGBLOB

A string with a maximum length of 4294967295 characters.

 

Date / Time

 DATE

YYYY-MM-DD

DATETIME

YYYY-MM-DD HH:MM:SS

TIMESTAMP

YYYYMMDDHHMMSS

TIME

HH:MM:SS

 

Apart from above there are some other data types in MySQL.

ENUM

To store text value chosen from a list of predefined text values

SET

This is also used for storing text values chosen from a list of predefined text values. It can have multiple values.

BOOL

Synonym for TINYINT(1), used to store Boolean values

BINARY

Similar to CHAR, difference is texts are stored in binary format.

VARBINARY

Similar to VARCHAR, difference is texts are stored in binary format.

 

Now let's see a sample SQL query for creating a table which has data of all data types. Study it and identify how each data type is defined.

CREATE TABLE`all_data_types` (
    `varchar` VARCHAR( 20 )  ,
    `tinyint` TINYINT  ,
    `text` TEXT  ,
    `date` DATE  ,
    `smallint` SMALLINT  ,
    `mediumint` MEDIUMINT  ,
    `int` INT  ,
    `bigint` BIGINT  ,
    `float` FLOAT( 10, 2 )  ,
    `double` DOUBLE  ,
    `decimal` DECIMAL( 10, 2 )  ,
    `datetime` DATETIME  ,
    `timestamp` TIMESTAMP  ,
    `time` TIME  ,
    `year` YEAR  ,
    `char` CHAR( 10 )  ,
    `tinyblob` TINYBLOB  ,
    `tinytext` TINYTEXT  ,
    `blob` BLOB  ,
    `mediumblob` MEDIUMBLOB  ,
    `mediumtext` MEDIUMTEXT  ,
    `longblob` LONGBLOB  ,
    `longtext` LONGTEXT  ,
    `enum` ENUM( '1', '2', '3' )  ,
    `set` SET( '1', '2', '3' )  ,
    `bool` BOOL  ,
    `binary` BINARY( 20 )  ,
    `varbinary` VARBINARY( 20 )
) ENGINE= MYISAM ;

 

Best practices

  • Use upper case letters for SQL keywords i.e. "DROP SCHEMA IF EXISTS `MyFlixDB`;"
  • End all your SQL commands using semi colons.
  • Avoid using spaces in schema, table and field names. Use underscores instead to separate schema, table or field names.

MySQL workbench ER diagram forward engineering

MySQL workbench has utilities that support forward engineering. Forward engineering is a technical term is to describe the process of translating a logical model into a physical implement automatically.

We created an ER diagram on our ER modeling tutorial. We will now use that ER model to generate the SQL scripts that will create our database.

Creating the MyFlix database from the MyFlix ER model

1.       Open the ER model of MyFlix database that you created in earlier tutorial.

2.       Click on the database menu. Select forward engineer

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3.       Select the options shown below in the wizard that appears. Click next

 

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4.       The next screen shows the summary of objects in our EER diagram. Our MyFlix DB has 5 tables.  Keep the selections default and click Next.

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5.       The window shown below appears. This window allows you to preview the SQL script to create our database. We can save the scripts to a *.sql" file or copy the scripts to the clipboard. Click on next button

 

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6.       The next window,  allows you to connect to an instance of MySQL server. Click on the stored connection drop down list and select local host. Click Execute

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7. The window shown below appears after successfully creating the database on the selected MySQL server instance.


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Summary

  • Creating a database involves translating the logical database design model into the physical database.
  • MySQLsupports a number of data types for numeric, dates and strings values.
  • CREATE DATABSEcommand is used to create a database
  • CREATE TABLEcommand is used to create tables in a database
  • MySQL workbenchsupports forward engineering which involves automatically generating SQL scripts from the logical database model that can be executed to create the physical database

The Database along with Dummy Data is attached. We will be using this DB for all our further tutorials. Simple import the DB in MySQL Workbench to get started

Click Here To Download MyFlixDB

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