Group Functions - 2 |
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Sheila has looked up how to use the group functions. To specify a group function, you write the name of the function followed by an argument in parentheses. The argument can be a column name, an expression, or a constant. The COUNT function returns the number of non null values in a column. If you count the values of a primary key column, you will find the number of rows in a table because a primary key column cannot contain nulls.
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