Naming Convention including Hungarian Prefixes for use with SQL and C#
Rodes Design

Created: 2010-02-13 15:46
Updated: 2010-02-14 03:27


SQL Data Types

Pre	Size	SQL Data Types	Description  

bt 	1	bit			Integer data with either a 1 or 0 value  

bf	1-510	binary		Fixed-length binary data with a max length of 8,000 bytes  
bv	1-510	varbinary		Variable-length binary data with a max length of 8,000 bytes  

in 	4	int         	Integer data from -2^31 to 2^31 - 1  
ib 	8	bigint      	Integer data from -2^63 to 2^63-1  
id	1-8   identity          Integer data used as primary key
is 	2	smallint    	Integer data from -2^15 to 2^15 - 1  
it 	1	tinyint		Integer data from 0 to 255  

nm	5-17	numeric		Fixed precision and scale numeric data from -10^38 +1 to 10^38 -1  
nd	5-17	decimal		Fixed precision and scale numeric data from -10^38 +1 to 10^38 -1  

my 	8	money			Monetary data values from -2^63 to 2^63 - 1  
ms 	4	smallmoney		Monetary data values from -214,748.3648 to +214,748.3647  

rl	4	real			Floating precision number data from -3.40E + 38 to 3.40E + 38  
rb	8	float			Floating precision number data from -1.79E + 308 to 1.79E + 308  

dt 	8	datetime		Date-time data from 1/1/1753 to 12/31/9999, 3.33 milliseconds  
ds 	4	smalldatetime	Date-time data from 1/1/1900 to 6/6/2079, one minute  

cf 	1x	char			Fixed-length character data with a max length of 8,000 chars  
cv 	1x	varchar		Variable-length data with a max of 8,000 chars  
ct 	**	text			Variable-length data with a max length of 2^31 - 1 chars  

uf 	2x	nchar			Fixed-length Unicode data with a max length of 4,000 chars  
uv 	2x	nvarchar		Variable-length Unicode data with a max length of 4,000 chars  
ut 	**	ntext			Variable-length Unicode data with a max length of 2^30 - 1 chars  

mg 	**	image			Variable-length binary data with a max length of 2^31 - 1 bytes  

cr	**	cursor		A reference to a cursor  

sv	**	sql_variant		A data type that stores values of various data types

xm	**	xml

tb	**	table			A special data type used to store a result set for later processing  

gt	8  	timestamp		A database-wide unique number updated every time a row gets updated  
gu	16	uniqueidentifier	A globally unique identifier  

	**    Very large size limit

Notes:

* Keywords should be all lower case.

* Use camel case where the first letter is lowercase for variables, parameters, fields, and properties. Note that this varies from some conventions because it includes public variables.

* Use Pascal case where the first letter is uppercase for all other identifiers such as class names, method names, event names, namespaces, enums, etc. Examples: Main, MyClass, ConvertCurrency, Console.Writeline.

* Do not use underscore characters in identifiers but see exception below.

* Use two-character lower-case 'Hungarian' prefixes for all SQL columns as listed above. This is what MS used to call 'System Hungarian' and Joel Spolsky calls 'light Hungarian'. Changes to SQL column data types should be rare. When that must happen, it is worth considering every reference.

* Most common meaning of letter in the first position : 'b' binary or bit, 'i' integer, 'n' number, 'm' money, 'r' real number, 'd' date-time, 'c' character, 'u' unicode character, 'g' global. Exceptions: mg (image), cr (cursor). Use 'u' instead of 'n' to identify Unicode fields. The 'n' in nchar and nvarchar means 'national' but looks like 'n' for numeric.

* Most common meaning of letter in the second position : 's' small, 'b' big, 't' tiny, 'f' fixed, 'v' variable. Exceptions: dt (datetime), tb (table), gt (global timestamp)

* There is no difference between 'numeric' and 'decimal' but use nm for fields that contain natural numbers, nd for fields with decimal values.

* Use one-character lower-case prefixes for local working variables: b (bool), i (int), l(long), f (float), d (double), m (decimal), c (char), s (string). These letters follow the C# 'numeric suffix' letters. Examples: bOK, i1, i2, iPtr, fX, dBig, mCalc, c1, cFlag, sVowels.

* Use lower-case prefixes of three characters or more for public variables, parameters, fields, properties, etc. in C# code. These should reflect the usage of the data and would not directly correspond with SQL or internal data types. This is what MS used to call 'Apps Hungarian'. For instance 'dol' for dollar amounts and 'cent' for cents. A property such as 'dolPrice' or 'euroPrice' could have a C# data type of decimal. A property such as 'centBalance' which has no fractional part could be stored in a decimal or integer data type. More examples: heightWindow, widthWindow, heightForm, strLastName, rowPosition, colPosition, unsafeUserName, strFile, intFile, rstFile. When picking a prefix, go for the most important aspect of the variable. Do not combine aspects.

* TABLE names have no prefix but are typed in all upper-case. The primary key of table TABLE is idTABLE. When a table name appears as part of an identifier name, separate it with an underscore. Examples: CUSTOMER_Browse, ADDRESS_Lookup.

* Note that there is no letter to indicate scope as sometimes seen: m_ClassMember, g_nWheels. Instead the scope is roughly indicated by the length of the prefix: 1 letter = local variable, 2 letters = table column, 3+ letters = class member, etc.