Skip to main content

MySQL Data Types and Properties

MySQL Data Types and Properties

Have a look at the following line of code from the post Storing and Retrieving Data from MySQL Database.

CREATE TABLE phno(
name varchar( 50 ) ,
phnum varchar( 20 )
)

As I told you we have to declare the column data types while creating tables depending on the values we want to store. MySQL has wide variety of data types, out of which I’m stating some of the important ones below:

  1. CHAR: For storing character and string data, faster than VARCHAR.

  2. VARCHAR: For storing character and string data. Slower but efficient in storing variable length string as only the needed memory is used no matter how much we allocate.

  3. INT: For storing regular integers. Same as INTEGER, other related data types are TINYINT, SMALLINT, MEDIUMINT, BIGINT.

  4. FLOAT: For storing floating point values, it is 4 bytes long. There is also a DOUBLE which is 8 bytes long.

  5. DATE: For storing YYYY-MM-DD date values.

Besides data types we can also assign column fields some properties to change the way they store data. These are some of the useful ones:

  1. NOT NULL: This specifies that a particular field cannot be empty. When inserting data you must provide data for this field or else MySQL generates error. It is used to make sure value for certain column is always provided.

  2. AUTO_INCREMENT: This property can be used with integer field to automatically make MySQL insert serial numbers to each row inserted.

  3. PRIMARY KEY: primary key is very important property of a table. It helps MySQL speed up query processing. Usually, serial number column field is defined as a primary key but it can be any field which is unique for each row.

The following SQL code illustrates how the above properties are used:

CREATE TABLE temp(
id integer AUTO_INCREMENT PRIMARY KEY ,
name varchar( 20 ) NOT NULL
)

It is a good idea to always have an extra column for each table. This column should be defined as both AUTO_INCREMENT and PRIMARY KEY.

Previous Articles:

Popular posts from this blog

Fix For Toshiba Satellite "RTC Battery is Low" Error (with Pictures)

RTC Battery is Low Error on a Toshiba Satellite laptop "RTC Battery is Low..." An error message flashing while you try to boot your laptop is enough to panic many people. But worry not! "RTC Battery" stands for Real-Time Clock battery which almost all laptops and PCs have on their motherboard to power the clock and sometimes to also keep the CMOS settings from getting erased while the system is switched off.  It is not uncommon for these batteries to last for years before requiring a replacement as the clock consumes very less power. And contrary to what some people tell you - they are not rechargeable or getting charged while your computer or laptop is running. In this article, we'll learn everything about RTC batteries and how to fix the error on your Toshiba Satellite laptop. What is an RTC Battery? RTC or CMOS batteries are small coin-shaped lithium batteries with a 3-volts output. Most laptops use

The Best Way(s) to Comment out PHP/HTML Code

PHP supports various styles of comments. Please check the following example: <?php // Single line comment code (); # Single line Comment code2 (); /* Multi Line comment code(); The code inside doesn't run */ // /* This doesn NOT start a multi-line comment block /* Multi line comment block The following line still ends the multi-line comment block //*/ The " # " comment style, though, is rarely used. Do note, in the example, that anything (even a multi-block comment /* ) after a " // " or " # " is a comment, and /* */ around any single-line comment overrides it. This information will come in handy when we learn about some neat tricks next. Comment out PHP Code Blocks Check the following code <?php //* Toggle line if ( 1 ) {      // } else {      // } //*/ //* Toggle line if ( 2 ) {      // } else {      // } //*/ Now see how easy it is to toggle a part of PHP code by just removing or adding a single " / " from th

Designing a Simple Order Form Application in PHP

Ok guys, for this post we’re going to create a simple yet complete order form page. Order forms are used on many sites to take customers order online. Order forms should have the capability to take orders from visitors regarding what items they want to purchase and store the information for further processing. For this post’s example, we are going to create an order form for a Book Seller. The form will be designed to take order of five different items (books). Our order form application should be able to take order of five different items in any separate quantities tht user wants, it should also ask for shipping address and name of the customer. It should then store the information provided in a file along with the date and time order was placed. The application should also be able to take any number of orders and store them all linearly for further human processing. For this, we need a front end of a HTML form to which the user would interact a