SQL SERVER – Difference and Explanation among DECIMAL, FLOAT and NUMERIC

The basic difference between Decimal and Numeric :
They are the exactly same. Same thing different name.

The basic difference between Decimal/Numeric and Float :
Float is Approximate-number data type, which means that not all values in the data type range can be represented exactly.
Decimal/Numeric is Fixed-Precision data type, which means that all the values in the data type reane can be represented exactly with precision and scale.

Converting from Decimal or Numeric to float can cause some loss of precision. For the Decimal or Numeric data types, SQL Server considers each specific combination of precision and scale as a different data type. DECIMAL(2,2) and DECIMAL(2,4) are different data types. This means that 11.22 and 11.2222 are different types though this is not the case for float. For FLOAT(6) 11.22 and 11.2222 are same data types.

Reference : Pinal Dave (https://blog.sqlauthority.com), BOL DataTypes

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93 Comments. Leave new

  • What do you mean by data-type reane?

    Reply
  • Nice blog.very interesting topic, decimal float and numeric.

    Reply
  • DECLARE @num float , @num1 Dec(19,2)
    SET @num=950000.64
    SET @num1=@num
    SELECT CAST(@num1 as VARCHAR(18)),CAST(@num as VARCHAR(18)),@num

    ideally all 3 should have same value. But I am getting different values..

    Reply
  • Even without using @num1 = @num, same reult is coming….

    DECLARE @num float , @num1 Dec(19,2)
    SET @num=950000.64
    SET @num1=950000.64
    SELECT CAST(@num1 as VARCHAR(18)),CAST(@num as VARCHAR(18)),@num

    Reply
  • I also observed that LEN() function is behaving differently for float & decimal data types..
    Example:
    declare @a float, @b float, @c decimal(19,2)
    select @a = 350470.88, @b = 35070.88, @c = 350470.88
    select @a A, @b B, @c C, LEN(@a) len_A, LEN(@b) len_B, LEN(@c) len_C

    Ideally len_A & len_C should have same value…

    Reply
  • In T-SQL, I have a table with Lat/Long stored in real data types. However they only show up at scale of 4 such as -110.8130 / 31.3580. When I convert the column data types to Decimal (18,8), all of Lat/Long become -110.81304932 / 31.35803986. Is there any way I can control the “display” precision/scale when looking at real data type?

    Reply
  • I thinks we can’t create a column with data type decimal(2,4) as precision will not be less than scale.

    Reply

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