How Can I Count Character Occurrences in SQL Columns?

Count the number of occurrences of characters in SQL columns

In SQL, sometimes it is necessary to determine the frequency of occurrence of a specific character in a text column. For example, given a column containing a string consisting of 'Y' and 'N' characters, the task might be to count the number of instances of 'Y'.

Solution

To solve this problem, you can use the following methods:

Method 1: Use string replacement

This method uses the REPLACE() function to temporarily modify the string and replace the required characters with an empty string. The length difference between the original string and the modified string provides the number of character occurrences:

SELECT LEN(REPLACE(col, 'N', ''))

Method 2: Use characters to exclude

If the goal is not only to count non-'N' characters, but specifically to count the occurrences of 'Y', you need to modify the method slightly:

SELECT LEN(col) - LEN(REPLACE(col, 'Y', ''))

In this case, the length of the original string is reduced by the length of the modified string (in which all 'Y' characters are excluded), effectively providing a count of the number of occurrences of 'Y'.

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