How does SQL Server know what precision to use for money - sql-server

Question

How does SQL Server know to retrieve these values this way?
Key someMoney
----------- ---------------------
1 5.00
2 5.002
3 5.0001
Basically, I'm wondering how to know how many decimal places there are without much of a performance hit.
I want to get
Key someMoney places
----------- --------------------- ----------
1 5.00 2
2 5.002 3
3 5.0001 4

Answer 1

Money has 4 decimal places....it's a fixed-point data type.
http://msdn.microsoft.com/en-us/library/ms179882.aspx
Is SQL Server 'MONEY' data type a decimal floating point or binary floating point?

Answer 2

So this is a huge ugly hack, but it will give you the value you're looking for...
DECLARE #TestValue MONEY
SET #TestValue = 1.001
DECLARE #TestString VARCHAR(50)
SET #TestString = REPLACE(RTRIM(REPLACE(CONVERT(VARCHAR, CONVERT(DECIMAL(10,4), #TestValue)), '0', ' ')), ' ', '0')
SELECT LEN(#TestString) - CHARINDEX('.', #TestString) AS Places

Answer 3

This produces the correct results, but I'm not sure if it performs well enough for you and I haven't tried it with data other than the examples you listed:
;
with money_cte ([Key], [someMoney])
as
(
select 1, cast(5.00 as money)
union
select 2, cast(5.002 as money)
union
select 3, cast(5.0001 as money)
)
select [Key], [someMoney], abs(floor(log10([someMoney] - round([someMoney], 0, 1)))) as places
from money_cte
where [someMoney] - round([someMoney], 0, 1) <> 0
union
select [Key], [someMoney], 2 as places
from money_cte
where [someMoney] - round([someMoney], 0, 1) = 0

Answer 4

The client is formatting that. SQL Server SSMS or whatever. SQL Server is returning a full money value in the data stream and it takes a full 8 bytes. (http://msdn.microsoft.com/en-us/library/cc448435.aspx). If you have SQL Server convert to varchar, it defaults to 2 decimal places
Notice that the Stack Overflow data browser doesn't even show the same results you have:
https://data.stackexchange.com/stackoverflow/q/111288/
;
with money_cte ([Key], [someMoney])
as
(
select 1, cast(5.00 as money)
union
select 2, cast(5.002 as money)
union
select 3, cast(5.0001 as money)
)
select *
, CONVERT(varchar, someMoney) AS varchar_version
, CONVERT(varchar, someMoney, 2) AS varchar_version2
FROM money_cte​