SQL Set Functions

Sometimes, the information that you want to extract from an SQL table doesn't relate to individual rows but rather to sets of rows. SQL provides five set (or aggregate) functions to deal with such situations — COUNT, MAX, MIN, SUM, and AVG. Each function performs an action that draws data from a set of rows rather than from a single row:

COUNT	Returns the number of rows in the specified table
MAX	Returns the maximum value that occurs in the specified table
MIN	Returns the minimum value that occurs in the specified table
SUM	Adds up the values in a specified column
AVG	Returns the average of all the values in the specified column

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