Examples
MID("123 Maple Dr", 5, 5)
: Maple
MID("123 Maple Dr", 5, 0)
returns blank.
Fractional Component of Decimal Value
The integer component of a Decimal value in the Result column:
NUMBER(
MID(
TEXT([Result]),
(FIND(".", TEXT([Result])) + 1),
LEN(TEXT([Result]))
)
)

TEXT([Result])
converts the Decimal value to a Text value. The textual functions used in this example interpret nontextual values differently. Using TEXT() ensures the Result column value is interpreted the same by each function. 
(FIND(".", ...) + 1)
locates the beginning of the fractional component as the position immediately after the decimal point in the value. 
MID(..., ..., LEN(...))
extracts the fractional part using a howmany value guaranteed to cover the entire fractional component. 
NUMBER(...)
converts the extracted text to a Number.
See also: FIND(), LEN(), NUMBER(), TEXT()
Syntax
MID( sometext , beginat , howmany )
Arguments
 sometext (any textual type)
 beginat (Number) : The position, equal to or greater than 1, of the first character in sometext to return. A nonNumber value may be accepted but may produce unexpected results.
 howmany (Number) : The nonnegative number of characters from sometext to return. A nonNumber value may be accepted but may produce unexpected results.
Return Value
Text: The howmany characters beginning at position beginat from sometext. If howmany is greater than the remaining length of sometext, the remainder of sometext is returned.