PHP array

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  An array stores multiple values in one single variable. In PHP, the array() function is used to create an array. Example: <?php $pets = array ( "dog" , "cat" , "rabbit" ); echo $pets [ 0 ] . "," . $pets [ 1 ] . "," . $pets [ 2 ]; ?> Output: dog,cat,rabbit An array is a special variable, which can hold more than one value at a time. If you have a list of student names, storing the names in single variables could like this, $name1 = "Peter" $name2 = "Mickle" $name2 = "Bravo" However, what if you want to loop through the names and find a specific one? And what if you had 3 names, but 1000? The solution is to create an array . An array can hold many values under a single name, and you can access the values by referring to an index number. There are three different kind of arrays. Numeric array – Arrays with a numeric index Associative array – Arrays with named keys
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Find Duplicate Records in MySQL Table

Find Duplicate Records in MySQL Table


In this post, you will learn how to find duplicate values of one or more columns in MySQL table.

Find duplicate values in one column

The find duplicate values in on one column of a table, you use follow these steps:-

  1. First, use the GROUP BY clause to group all rows by the target column, which is the column that you want to check duplicate.
  2. Then, use the COUNT() function in the HAVING clause to check if any group have more than 1 element. These groups are duplicate.
Syntax:
 SELECT
   col,
   COUNT(col)
 FROM
   table_name
 GROUP BY col
 HAVING COUNT(col) > 1;

Find duplicate values in multiple columns

Sometimes, you want to find duplicate rows based on multiple columns instead of one. In this case, you can use the following query:-

Syntax:
 SELECT
   col1, COUNT(col1),
   col2, COUNT(col2),
   .....
 FROM
   table_name
 GROUP BY
   col1,
   col2,
   .....
 HAVING
   (COUNT(col1) > 1) AND
   (COUNT(col1) > 2) AND
   .....

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