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 12 Functions and Operators
 **************************
 

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* non-typed-operators          Operators
* control-flow-functions       Control Flow Functions
* string-functions             String Functions
* numeric-functions            Numeric Functions
* date-and-time-functions      Date and Time Functions
* mysql-calendar               What Calendar Is Used By MySQL?
* fulltext-search              Full-Text Search Functions
* cast-functions               Cast Functions and Operators
* other-functions              Other Functions
* group-by-functions-and-modifiers  Functions and Modifiers for Use with `GROUP BY' Clauses
 
 Expressions can be used at several points in SQL statements, such as in
 the `ORDER BY' or `HAVING' clauses of `SELECT' statements, in the
 `WHERE' clause of a `SELECT', `DELETE', or `UPDATE' statement, or in
 `SET' statements. Expressions can be written using literal values,
 column values, `NULL', built-in functions, stored functions,
 user-defined functions, and operators. This chapter describes the
 functions and operators that are allowed for writing expressions in
 MySQL. Instructions for writing stored functions and user-defined
 functions are given in  stored-procedures, and 
 adding-functions.
 
 An expression that contains `NULL' always produces a `NULL' value
 unless otherwise indicated in the documentation for a particular
 function or operator.
 
 * By default, there must be no whitespace between a function name
 and the parenthesis following it.  This helps the MySQL parser
 distinguish between function calls and references to tables or columns
 that happen to have the same name as a function. However, spaces around
 function arguments are permitted.
 
 You can tell the MySQL server to accept spaces after function names by
 starting it with the -sql-mode=IGNORE_SPACE option. (See 
 server-sql-mode.) Individual client programs can request this
 behavior by using the `CLIENT_IGNORE_SPACE' option for
 `mysql_real_connect()'. In either case, all function names become
 reserved words.
 
 For the sake of brevity, most examples in this chapter display the
 output from the `mysql' program in abbreviated form. Rather than
 showing examples in this format:
 
      mysql> SELECT MOD(29,9);
      +-----------+
      | mod(29,9) |
      +-----------+
      |         2 |
      +-----------+
      1 rows in set (0.00 sec)
 
 This format is used instead:
 
      mysql> SELECT MOD(29,9);
              -> 2
 

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