title: SQL - find if a column has more than one distinct value
body: <p>I'm going through columns in a large table, and I want to find out if the column has more than one distinct value. I don't care what the values are or how many distinct values there are, I just need to return true if we have more than one distinct value (i.e. two rows with different values for that column) and false otherwise. Performance is my main concern. What's the best way to implement this in SQL? </p>
  
  <p>EDIT: Table has 1M+ rows on MSSQL. The columns have multiple data types; some are nullable and some are not. </p>