In this tutorial you can learn how to work with NULL in MySQL tables: Insert, Update, and Select columns with NULL value.

Add column with NULL value

To insert into a MySQL table rows with columns having NULL, add the NULL value without quotes.
$sql = "INSERT INTO `table_name`
 (`column1`, `column2`, `column3`)
 ('val1', NULL, 'val3')";

Or, if the NULL value is stored into a variable, add "NULL" as a string to that variable, then write the variable into the SQL query, without quotes.
$nul = 'NULL';
$sql = "INSERT INTO `table_name`
 (`column1`, `column2`, `column3`)
 ('val1', $nul, 'val3')";

- If you create the $nul value like this:   $nul = NULL; , the SQL query will contain nothing in the place where this variable is added. Will result:
INSERT INTO `table_name` (`column1`, `column2`, `column3`) VALUES ('val1', , 'val3')

- If you want to insert the string "NULL", add it within quotes:
$sql = "INSERT INTO `table_name`
 (`column1`, `column2`, `column3`)
 ('val1', 'NULL', 'val3')";

UPDATE with NULL value

The same works with UPDATE.
$sql = "UPDATE `table_name` SET `column1`='val1', `column2`=NULL, WHERE `column3`='val3'";
$nul = 'NULL';
$sql = "UPDATE `table_name` SET `column1`='val1', `column2`=$nul, WHERE `column3`='val3'";

SELECT fields with NULL value

To select rows in a MySQL table according to columns with NULL value, use IS NULL.
$sql = "SELECT * FROM `table_name` WHERE `column` IS NULL";

If you want to Not return the rows with a specific NULL field, use IS NOT NULL.
$sql = "SELECT * FROM `table_name` WHERE `column` IS NOT NULL";

Daily Test with Code Example

Which type of <input> creates a color well control for selecting a color value?
type="text" type="color" type="date"
<input type="color" name="get_color" />
Which CSS method rotates the HTML element at a given degree?
scale() translate() rotate()
#some_id:hover {
  transform: rotate(60deg);
  -ms-transform: rotate(60deg);    /* IE 9 */
  -moz-transform: rotate(60deg);   /* Firefox */
Click on the function that returns the number with the highest value.
pow() min() max()
var maxn = Math.max(8, 4, 88, 56);
alert(maxn);      // 88
Which function prevent the same file from being included more than once in a page?
include() include_once() require()
Insert, Select and Update NULL value in MySQL

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