Aggregate function

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In computer science, an aggregate function is a function that returns a single value from a collection of input values such as a set, a bag or a list.

Common aggregate functions include:

• Average()
• Count()
• Maximum()
• Mean()
• Minimum()
• Mode()
• Sum()

Aggregate functions are common in numerous programming languages such as Ruby, in spreadsheets, and in relational algebra.

SQL Aggregate Functions

SQL aggregate functions return a single value, calculated from values in a column.

Useful aggregate functions:

   * AVG() - Returns the average value
   * COUNT() - Returns the number of rows
   * FIRST() - Returns the first value
   * LAST() - Returns the last value
   * MAX() - Returns the largest value
   * MIN() - Returns the smallest value
   * SUM() - Returns the sum

SQL Scalar functions

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SQL scalar functions return a single value, based on the input value.

Useful scalar functions:

   * UCASE() - Converts a field to upper case
   * LCASE() - Converts a field to lower case
   * MID() - Extract characters from a text field
   * LEN() - Returns the length of a text field
   * ROUND() - Rounds a numeric field to the number of decimals specified
   * NOW() - Returns the current system date and time
   * FORMAT() - Formats how a field is to be displayed

See also

• Group by (SQL), SQL implementation

References

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