Updating column 1 or column 2 with value of same column value or different column value of same table

Some time we need to change values of columns of same row of a table.

update  table_name set column1 = column2

you can also put some arithmetic calculation and update table as well. the above query will take the value of column2 and will store it in the column1 of the same row of same table.

UNIX Command file lists order by file size

below command will list all files in a folder order by file size.

ls -l | sort +4rn |awk '{print $9, $5}'

json serialization

What is JSON

Json stands for JavaScript Object Notification. it represents data in object format so that javascript and understand it easily and manipulate it easily

it looks like as below:

[{"id":"83","text":"sales crescent"},{"id":"88","text":"sales grey bar"}]

 its just a simple array of two json object

keep in mind that, if you will find [] symbol it means it's a array of object. that means one or more then one json object may be there inside the space

like bellow

var mathTen = 

[{

"name": "Aniruddha Das",

"email": "someemailaddress@gmail.com

"valuepaids": [{"id":"83","text":"sales crescent"},{"id":"88","text":"sales grey bar"}]

}]

you can also iterate this object by using jQuery.each() ot any normal javascript loop.

here variable mathTen contain a array of json. again inside mathTen there valuepaids node which contains a array of json object.

there are ways to manipulate these json object hierarchy inside in side javascript code (i am not mentioning here as we can do that , i think so :) )

Where we need json serialization:

We need json serialization where we want to pass json from one place to another. like from one environment to another. like while sending json data from java/php/asp.net codes to javascript code thorugh ajax call.

Or sending json data as parameter from a dynamically created javascript function

But in some situations we need to create dynamic html codes and pass as json as as parameters if we are creating dynamic javascript functions in that like below

var yuyu = [{"id":"83","text":"sales crescent"},{"id":"88","text":"sales grey bar"}];
indObj=[{"id":"83","text":"sales crescent"}];


$("#divAllIndividuals")
            .append(""+indObj[0].text++indObj[0].id+"','"+JSON.stringify(yuyu)+"','"+JSON.stringify(indObj)+"','"+indObj[0].text+"') title=\"Delete Entry\">\"");

there json variable (yuyu and indObj) will no more will be json in the called function if you will not serialize these function here. here the serialize concept come

what is json serialization:

Json serialization is nothing but it convert json object to string so that you can easily send that string from one environment to another or you can pass that string as parameter from a dynamically created javascript function.

Use of json serialization:

to serialize a json object we can use JSON.stringify() as we did in the above created dynamically created javascript function. this function will convert json object to string.

Again we have to deserialize the json object string in the called function  (if we are calling in as parameter in dynamic javascript function) or if we are receiving it from other language like java/php/asp.net.

to deserilize json object string we need to call JSON.parse(); it will again convert josn object string to json object so that we can use json nodes in your program.

var indObj = $.parseJSON(jsonpassedvariablehere);

that it. now you can send json data from anywhere in your program and can use that anywhere in your program by serialize and deserialize the objects

Thanks 

What is the difference between visibility:hidden and display:none

visibility:hidden and display:none are not synonims.

display:none means that the the tag in question will not appear on the page at all (although you can still interact with it through the dom). There will be no space allocated for it between the other tags. 


Visibility:hidden means that unlike display:none, the tag is not visible, but space is allocated for it on the page. so for example