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To count number of columns in a table with jQuery, use the each() function with attr(). You can try to run the following code to learn how to count column in a table:EaxmpleLive Demo jQuery Example $(document).ready(function(){ var num = 0; $('tr:nth-child(1) td').each(function () { if ($(this).attr('colspan')) { num += +$(this).attr('colspan'); } else { num++; } }); alert("Total Columns= "+num); }); -1st column- -2nd column- -3rd column-
To check if table row exists or not, use the is() method, with the :visible selector −if($(".row").is(":visible")) { alert("Visible!"); }You can try to run the following code to learn how to chck if a row exists or not. It even notifies when a new row is created −ExampleLive Demo jQuery - Add Table Rows table{ width: 100%; margin: 25px 0; border-collapse: collapse; } table, th, td{ border: 1px solid #6C220B; } table th, table td{ padding: 8px; text-align: left; } ... Read More
To call a jQuery function after a certain delay, use the siteTimeout() method. Here, jQuery fadeOut() function is called after some seconds.You can try to run the following code to learn how to work with setTimeout() method in jQuery to call a jQuery function after a delay −ExampleLive Demo $(document).ready(function(){ $("#button1").bind("click",function() { setTimeout(function() { $('#list').fadeOut();}, 2000); }); }); Voice Speak Write The above content will fade out after 2 seconds
There may be times when the SQL query was expecting some data type but it got another. In that case type conversion is done by SQL. This is implicit type conversion. However, sometimes the programmer explicitly converts one data type into another in a query. This is known as explicit type conversion. Both of these in detail are given as follows:Implicit Data Type ConversionIn implicit data type conversion, the SQL programmer does not specify anything. Rather the system converts one type of data to another as per its requirements. For example - a numeric data type can be converted to ... Read More
Mathematical functions are very important in SQL to implement different mathematical concepts in queries.Some of the the major mathematical functions in SQL are as follows −ABS(X)This function returns the absolute value of X. For example −Select abs(-6);This returns 6.MOD(X, Y)The variable X is divided by Y and their remainder is returned. For example −Select mod(9, 5);This returns 4.SIGN(X)This method returns 1 if X is positive, -1 if it is negative and 0 if the value of X is 0. For example −Select sign(10);This returns 1.FLOOR(X)This returns the largest integer value that is either less than X or equal to it. ... Read More
As we know that MySQL will produce an error if overflow occurs during the assessment of numeric expressions. For example, the largest signed BIGNT is 9223372036854775807, so the following expression will produce an error −mysql> Select 9223372036854775807 + 1; ERROR 1690 (22003): BIGINT value is out of range in '(9223372036854775807+1)'MySQL can handle such kind of overflows in following ways:BY CONVERTING VALUE TO UNSIGNEDMySQL enables such kind of operations by converting the values to unsigned as follows −mysql> Select CAST(9223372036854775807 AS UNSIGNED) +1; +------------------------------------------+ | CAST(9223372036854775807 AS UNSIGNED) +1 | +------------------------------------------+ | ... Read More
When we insert NULL value to AUTO_INCREMENT column, MySQL will return sequence number.Examplemysql> Create table employee(id INT NOT NULL PRIMARY KEY AUTO_INCREMENT, Name Varchar(10)); Query OK, 0 rows affected (0.16 sec) mysql> Insert into employee(id, Name) values(NULL, 'Gaurav'); Query OK, 1 row affected (0.07 sec) mysql> Select * from employee; +----+---------+ | id | Name | +----+---------+ | 1 | Gaurav | +----+---------+ 1 row in set (0.00 sec)
When we use AUTO_INCREMENT on a MySQL column, the sequence number always increases in ascending order starting from the default value 1 or from the value we specify.That is the reason, MySQL does not allow changing the AUTO_INCREMENT value to a value which is less than the current sequence number. It can be understood with the help of the following example −ExampleIn this example suppose we have a table named ‘emp1’ and while creating the table we specify the AUTO_INCREMENT VALUE to 100. Hence after inserting the values in table, the sequence would start from 100 onwards as can be ... Read More
MySQL AUTO_INCREMENT value starts from 1 but we can change it with the help of following two ways −With the help of ALTER TABLE query We can use ALTER TABLE query to change the staring value of AUTO_INCREMENT as follows −ALTER TABLE table_name AUTO_INCREMENT = value;ExampleSuppose we have created a table having column ‘id’ as AUTO_INCREMENT. Now if we will insert the values in it then the sequence number would start from 1 as you can see this in following queries −mysql> Create Table EMP(id int NOT NULL PRIMARY KEY AUTO_INCREMENT, NAME VARCHAR(10)); Query OK, 0 rows affected (0.07 sec) ... Read More
To know which key was pressed in a form input using jQuery, use the jQuery keydown event. You can try to run the following code to learn how to detect key pressed in a form input −ExampleLive Demo $(document).ready(function(){ $('#myinput').keydown(function(e) { var newkey = 'Key code = ' + e.which + ' ' + (e.ctrlKey ? 'Ctrl' : '') + ' ' + (e.shiftKey ? 'Shift' : '') + ' ' + (e.altKey ? 'Alt' : ''); $('#mykey').text(newkey); return false; }); }); Press any key: The key you press is visible here with keycode.