[sql] cast or convert a float to nvarchar?

I need to select from one column of datatype float and insert it in another column as nvarchar.

I tried to cast it: cast([Column_Name] as nvarchar(50))

The result was 9.07235e+009 instead of a 10 digit number (phone number).

Does any one know how to cast or convert this data properly?

Check STR. You need something like SELECT STR([Column_Name],10,0) ** This is SQL Server solution, for other servers check their docs.

DECLARE @MyFloat [float]

SET @MyFloat = 1000109360.050

SELECT REPLACE (RTRIM (REPLACE (REPLACE (RTRIM ((REPLACE (CAST (CAST (@MyFloat AS DECIMAL (38 ,18 )) AS VARCHAR( max)), '0' , ' '))), ' ' , '0'), '.', ' ')), ' ','.')

If you're storing phone numbers in a float typed column (which is a bad idea) then they are presumably all integers and could be cast to int before casting to nvarchar.

So instead of:

select cast(cast(1234567890 as float) as nvarchar(50))
1.23457e+009

You would use:

select cast(cast(cast(1234567890 as float) as int) as nvarchar(50))
1234567890

In these examples the innermost cast(1234567890 as float) is used in place of selecting a value from the appropriate column.

I really recommend that you not store phone numbers in floats though!
What if the phone number starts with a zero?

select cast(0100884555 as float)
100884555

Whoops! We just stored an incorrect phone number...

Float won't convert into NVARCHAR directly, first we need to convert float into money datatype and then convert into NVARCHAR, see the examples below.

Example1

SELECT CAST(CAST(1234567890.1234  AS FLOAT) AS NVARCHAR(100))

output

1.23457e+009

Example2

SELECT CAST(CAST(CAST(1234567890.1234  AS FLOAT) AS MONEY) AS NVARCHAR(100))

output

1234567890.12

In Example2 value is converted into float to NVARCHAR

For anyone willing to try a different method, they can use this:

select FORMAT([Column_Name], '') from YourTable

This will easily change any float value to nvarchar.

Do not use floats to store fixed-point, accuracy-required data. This example shows how to convert a float to NVARCHAR(50) properly, while also showing why it is a bad idea to use floats for precision data.

create table #f ([Column_Name] float)
insert #f select 9072351234
insert #f select 907235123400000000000

select
    cast([Column_Name] as nvarchar(50)),
    --cast([Column_Name] as int), Arithmetic overflow
    --cast([Column_Name] as bigint), Arithmetic overflow
    CAST(LTRIM(STR([Column_Name],50)) AS NVARCHAR(50))
from #f

Output

9.07235e+009    9072351234
9.07235e+020    907235123400000010000

You may notice that the 2nd output ends with '10000' even though the data we tried to store in the table ends with '00000'. It is because float datatype has a fixed number of significant figures supported, which doesn't extend that far.

You can also do something:

SELECT CAST(CAST(34512367.392 AS decimal(30,9)) AS NVARCHAR(100))

Output: 34512367.392000000