DERIVED FIELDS

[critzos]

How does one create a derived field (column) in a table? I.E. The table has 4 columns (for example) and the 4th column should be the sum of the other 3. Also, can one make a field's (columns) property such that nothing can be entered into the field? Thanks in advance.

 

[tlbroadbent]

If you are using SQL 2000, read in SQL Books Online about "Computed Columns." Earlier versions did not have computed columns. You can always return a computed or derived value in a query in any version of SQL Server.

Select Col1, Col2, Col3, Col4=Col1+Col2+Col3
From YourTable Terry L. Broadbent - DBA
Computing Links:

http://tlbroadbent.home.attbi.com/prog.htm

faq183-874 contains "Suggestions for Getting Quick and Appropriate Answers" to your questions.

 

[Gundapaneni]

Hi,
While creating a table itself you can create the computed field. Suppose you want to create a column as sum of two already delcared columns, you can create as follows

create table test
(a int,
b int,
c as a+b)

Here the column C is stored the date vartually in the table , it cannot appear physically in the table.
For more details read BOL, topic is CREATE TABLE <computed_cloumn>

Madhu.