PPT Slide
ALL and DISTINCT are keywords used to select either ALL (default) or the "distinct" or unique records in your query results. If you would like to retrieve just the unique records in specified columns, you can use the "DISTINCT" keyword. DISTNCT will discard the duplicate records for the columns you specified after the "SELECT" statement: For example:
SELECT DISTINCT city FROM snv_Class;
This statement will return all of the unique cities in the snv_Class table.