Added randomGaussian function

Author: bstjean

Functions_and_procedures/randomGaussian.sql

@@ -0,0 +1,56 @@
+SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='STRICT_TRANS_TABLES';
+
+DROP FUNCTION IF EXISTS randomGaussian;
+
+DELIMITER //
+
+CREATE FUNCTION randomGaussian (mu DOUBLE, sigma DOUBLE) 
+RETURNS DOUBLE
+NOT DETERMINISTIC
+NO SQL
+SQL SECURITY DEFINER
+COMMENT 'Returns a random number based on a normal (gaussian) distribution. (v1.00)'
+
+/*****************************************************************************
+*
+* DESCRIPTION:	Returns a random number based on a normal (gaussian) distribution.
+* 
+* AUTHOR:		Benoît St-Jean <bstjean@yahoo.com>
+* URL:		 	http://www.endormitoire.wordpress.com
+* VERSION: 		1.00
+*
+* USAGE:		SELECT randomGaussian(12.5, 3.2216);
+* RESULT: 		10.284951047046617 (this function is NOT deterministic!)
+*
+* PARAMETERS:	mu 		mean of the gaussian distribution
+*				sigma	standard deviation of the gaussian distribution
+*
+* RETURN:		DOUBLE
+*
+* NOTES:		n/a
+*		
+******************************************************************************/
+BEGIN 
+	DECLARE x DOUBLE;
+	DECLARE v1 DOUBLE;
+	DECLARE v2 DOUBLE;
+  
+	IF (mu IS NULL) THEN
+		SIGNAL SQLSTATE '45000'
+        SET MESSAGE_TEXT = 'Mean must not be NULL';
+	ELSEIF (sigma IS NULL) THEN
+        SIGNAL SQLSTATE '45000'
+        SET MESSAGE_TEXT = 'Standard deviation must not be NULL';
+    END IF;
+  
+	SET v1 := RAND();
+	SET v2 := RAND();
+
+	SET x := SQRT(-2.0 * LOG(v1)) * COS(2.0 * PI() * v2);
+	RETURN (mu + (sigma * x));
+	
+END//
+
+DELIMITER ;
+
+SET SQL_MODE=@OLD_SQL_MODE;

README.md

@@ -12,7 +12,8 @@ A collection of useful (I hope!) functions, stored procedures and SQL scripts to
 **isState** : Returns 1 if argument is an American 2-letter state code, 0 otherwise.  
 **isStrictlyAlpha** : Returns 1 if the string only contains [A-Za-z] characters, 0 otherwise  
 **lastindexof** : Returns the position of the last occurrence of a substring in a source string.  
-**occurrences** : Returns the number of occurrences of a search string inside a source string.   
+**occurrences** : Returns the number of occurrences of a search string inside a source string.  
+**randomGaussian** : Returns a random number based on a normal (gaussian) distribution.     
 **randomInt** : Returns a random positive integer between 2 unsigned integers *inclusively*     
 **removeAllChars** : Removes all characters in a string from a source string.  
 **replaceAllChars** : Replaces all characters in a string by a single replacement character from  source string.