declare @i int

select @i = 0

select datalength(@i)

quote:

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int, bigint, smallint, and tinyint
Exact number data types that use integer data.

bigint

Integer (whole number) data from -2^63 (-9223372036854775808) through 2^63-1 (9223372036854775807). Storage size is 8 bytes.

int

Integer (whole number) data from -2^31 (-2,147,483,648) through 2^31 - 1 (2,147,483,647). Storage size is 4 bytes. The SQL-92 synonym for int is integer.

smallint

Integer data from -2^15 (-32,768) through 2^15 - 1 (32,767). Storage size is 2 bytes.

tinyint

Integer data from 0 through 255. Storage size is 1 byte.

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decimal and numeric
Numeric data types with fixed precision and scale.

decimal[(p[, s])] and numeric[(p[, s])]

Fixed precision and scale numbers. When maximum precision is used, valid values are from - 10^38 +1 through 10^38 - 1. The SQL-92 synonyms for decimal are dec and dec(p, s).

p (precision)

Specifies the maximum total number of decimal digits that can be stored, both to the left and to the right of the decimal point. The precision must be a value from 1 through the maximum precision. The maximum precision is 38.

s (scale)

Specifies the maximum number of decimal digits that can be stored to the right of the decimal point. Scale must be a value from 0 through p. The default scale is 0; therefore, 0 <= s <= p. Maximum storage sizes vary, based on the precision.

Precision Storage bytes
1 - 9 5
10-19 9
20-28 13
29-38 17

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bit
Integer data type 1, 0, or NULL.

Remarks
Columns of type bit cannot have indexes on them.

Microsoft® SQL Server™ optimizes the storage used for bit columns. If there are 8 or fewer bit columns in a table, the columns are stored as 1 byte. If there are from 9 through 16 bit columns, they are stored as 2 bytes, and so on.

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money and smallmoney
Monetary data types for representing monetary or currency values.

money

Monetary data values from -2^63 (-922,337,203,685,477.5808) through
2^63 - 1 (+922,337,203,685,477.5807), with accuracy to a ten-thousandth of a monetary unit. Storage size is 8 bytes.

smallmoney

Monetary data values from - 214,748.3648 through +214,748.3647, with accuracy to a ten-thousandth of a monetary unit. Storage size is 4 bytes.

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float and real
Approximate number data types for use with floating point numeric data. Floating point data is approximate; not all values in the data type range can be precisely represented.

Syntax
float [ ( n ) ]

Is a floating point number data from - 1.79E + 308 through 1.79E + 308. n is the number of bits used to store the mantissa of the float number in scientific notation and thus dictates the precision and storage size. n must be a value from 1 through 53.

n is Precision Storage size
1-24 7 digits 4 bytes
25-53 15 digits 8 bytes


The Microsoft® SQL Server™ float[(n)] data type conforms to the SQL-92 standard for all values of n from 1 to 53. The synonym for double precision is float(53).

real

Floating point number data from –3.40E + 38 through 3.40E + 38. Storage size is 4 bytes. In SQL Server, the synonym for real is float(24).

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datetime and smalldatetime
Date and time data types for representing date and time of day.

datetime

Date and time data from January 1, 1753 through December 31, 9999, to an accuracy of one three-hundredth of a second (equivalent to 3.33 milliseconds or 0.00333 seconds). Values are rounded to increments of .000, .003, or .007 seconds, as shown in the table.

Example Rounded example
01/01/98 23:59:59.999 1998-01-02 00:00:00.000
01/01/98 23:59:59.995,
01/01/98 23:59:59.996,
01/01/98 23:59:59.997, or
01/01/98 23:59:59.998 1998-01-01 23:59:59.997
01/01/98 23:59:59.992,
01/01/98 23:59:59.993,
01/01/98 23:59:59.994 1998-01-01 23:59:59.993
01/01/98 23:59:59.990 or
01/01/98 23:59:59.991 1998-01-01 23:59:59.990


Microsoft® SQL Server™ rejects all values it cannot recognize as dates between 1753 and 9999.

smalldatetime

Date and time data from January 1, 1900, through June 6, 2079, with accuracy to the minute. smalldatetime values with 29.998 seconds or lower are rounded down to the nearest minute; values with 29.999 seconds or higher are rounded up to the nearest minute.

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