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 21.4 Rounding Behavior
 ======================
 
 This section discusses precision math rounding for the `ROUND()'
 function and for inserts into `DECIMAL' columns.
 
 The `ROUND()' function rounds differently depending on whether its
 argument is exact or approximate:
 
    * For exact-value numbers, `ROUND()' uses the `round half up' rule:
      A value with a fractional part of .5 or greater is rounded up to
      the next integer if positive or down to the next integer if
      negative. (In other words, it is rounded away from zero.) A value
      with a fractional part less than .5 is rounded down to the next
      integer if positive or up to the next integer if negative.
 
    * For approximate-value numbers, the result depends on the C
      library. On many systems, this means that `ROUND()' uses the
      `round to nearest even' rule: A value with any fractional part is
      rounded to the nearest even integer.
 
 The following example shows how rounding differs for exact and
 approximate values:
 
      mysql> SELECT ROUND(2.5), ROUND(25E-1);
      +------------+--------------+
      | ROUND(2.5) | ROUND(25E-1) |
      +------------+--------------+
      | 3          |            2 |
      +------------+--------------+
 
 For inserts into a `DECIMAL' column, the target is an exact data type,
 so rounding uses "round half up," regardless of whether the value to be
 inserted is exact or approximate:
 
      mysql> CREATE TABLE t (d DECIMAL(10,0));
      Query OK, 0 rows affected (0.00 sec)
 
      mysql> INSERT INTO t VALUES(2.5),(2.5E0);
      Query OK, 2 rows affected, 2 warnings (0.00 sec)
      Records: 2  Duplicates: 0  Warnings: 2
 
      mysql> SELECT d FROM t;
      +------+
      | d    |
      +------+
      | 3    |
      | 3    |
      +------+
 

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