Select the alpha prefix from a column of values

Symptoms

You have been given a list of values in a SQL table and wish to extract the alpha prefix, e.g. "INV123, CASE001, TICKET99" -> "INV, CASE, TICKET"

Cause

n/a

Resolution

SELECT col, CASE WHEN col LIKE '[A-Z]%' THEN LEFT(col, PATINDEX('%[^A-Za-z]%', col) - 1) ELSE '' END AS alpha_prefix FROM table