SQL Functions

Just like any other computer language, SQL supports the use of functions to manipulate with data. Function is a simple operations that are usually performed on data.

SQL has two categories of functions: set (aggregate) functions and scalar functions.

SQL Aggregate Functions

These functions take information from multiple table rows, process that information in some way, and deliver a single row answer.

Useful aggregate functions:

  • AVG() – Returns a column’s average value
  • COUNT() – Returns the number of rows in a table column
  • FIRST() – Returns the first value
  • LAST() – Returns the last value
  • MAX() – Returns the column’s largest value
  • MIN() – Returns the column’s smallest value
  • SUM() – Returns the sum of column’s values

The use of these functions is explained in the following sections.

SQL Scalar functions

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

Useful scalar functions:

  • UCASE() – Converts a table field to upper case
  • LCASE() – Converts a table 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
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