How to compare scientific notation and decimal numbers in mysql MIN() aggregate function?

问题

How can i apply mysql MIN() over mixed decimal value and scientific notation values. I need to get minimum distance using latitude longitude equation in a mysql query with MIN(). It is working if the distance are decimal. But it is not working properly, if some distance are too small like "5.89872212195226e-05"

The problem is MIN(4,5.89872212195226e-05) in a mysql query will always return '4'.

Here is the part of query

 MIN (
         (acos(sin((".$searchLat."*pi()/180)) * 
         sin((b_loc.locLatitude*pi()/180))+cos((".$searchLat."*pi()/180)) * 
         cos((b_loc.locLatitude*pi()/180))
         * cos(((".$searchlng."- b_loc.locLongitude)*pi()/180))))*180/pi())*60*1.1515
        ) as mindistance

Any solution? Thank You

回答1:

Cast to decimal should help :-

mysql> select cast( "5.89872212195226e-05"  as decimal(65,30));
+--------------------------------------------------+
| cast( "5.89872212195226e-05"  as decimal(65,30)) |
+--------------------------------------------------+
|                 0.000058987221219522600000000000 |
+--------------------------------------------------+

Example of comparison :-

mysql> select least( 4, cast("5.89872212195226e-05" as decimal(65,30)) );
+------------------------------------------------------------+
| least( 4, cast("5.89872212195226e-05" as decimal(65,30)) ) |
+------------------------------------------------------------+
|                           0.000058987221219522600000000000 |
+------------------------------------------------------------+

Example usage :-

MIN(cast( ...  as decimal(65,30)))

来源：https://stackoverflow.com/questions/8356104/how-to-compare-scientific-notation-and-decimal-numbers-in-mysql-min-aggregate

标签

mysql

aggregate-functions

scientific-notation