How Can I Filter SQL Results Using an Alias in the WHERE Clause?

Using an Alias in a Where Statement

In SQL, using an alias in a WHERE statement is not directly possible. However, there is an alternative approach that can achieve a similar effect: using the HAVING clause.

The HAVING clause is used to filter the results of a query after they have been grouped. It is similar to the WHERE clause, but it is applied after the grouping has been performed.

To use HAVING to filter by an alias, you can follow these steps:

1. Create an alias for the expression you want to filter by using the AS keyword.
2. Use the HAVING clause to filter the results by the alias.

For example, the following query uses an alias to filter the results of the MyTable table by the Col1 column:

SELECT
    SUBSTRING(Column1, 1, 4) + SUBSTRING(Column1, 4, 3)  AS Col1
FROM
    MyTable
HAVING
    Col1 = 'MySearch'

This query will return all rows from the MyTable table where the Col1 column is equal to 'MySearch'.

It's important to note that the HAVING clause is applied after the grouping has been performed. This means that if you are using the HAVING clause to filter the results of a grouped query, you must first group the results using the GROUP BY clause.

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