How Can I Efficiently Count Character Occurrences in an SQL Column?

Efficient way to count characters in SQL column

In data analysis, it is often necessary to count the number of occurrences of the 'Y' character in columns containing 'Y' and 'N' character sequences.

For Boolean values, an efficient method is to use the REPLACE() function:

<code class="language-sql">SELECT LEN(REPLACE(col, 'N', ''))</code>

This query replaces all 'N' values ​​with empty strings. Therefore, the number of non-'N' characters (effectively counting the occurrences of 'Y') is calculated by the LEN() function.

More generally, if the goal is to count the occurrences of any given character (e.g. 'Y') in a string column, you can use the following query:

<code class="language-sql">SELECT LEN(col) - LEN(REPLACE(col, 'Y', ''))</code>

This variation uses the same REPLACE() function but replaces the target character ('Y') with an empty string. The resulting length difference represents the count of the required characters ('Y') in the original string.

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