Counting Records

It is also very easy to count the number of records that meet a certain criteria. This function is performed with the COUNT operator and follows the syntax:

    SELECT COUNT (column_name)
    FROM table_name
    WHERE where_clause [optional];

In other words, to count the number of employees in the EMPLOYEES table, you would use:

    SELECT COUNT (EMP_NAME)
    FROM EMPLOYEES;

which would return the following:

    COUNT (EMP_NAME)
    -----------------
    3
    -----------------

Note that sometimes, it is preferable to use SELECT COUNT(*) instead of specifying a column_name. This is because the COUNT operator does not consider columns with null values. Thus, if you specified a column_name and one of the rows in that table had a null value for column_name, your count would be off. Using "*" assures that all rows are counted even if they include null values. And by the way, most implementations of SQL will also require you to use the DISTINCT operator if you specify a column_name.

Maximums and Minimums
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Distinct