Re: "Macro" statement

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From: --CELKO-- (jcelko212_at_earthlink.net)
Date: 01/26/05 

Date: 25 Jan 2005 16:42:22 -0800

>> Imagine that we have a table named tblA and fields [sic] with the
almost same name, for example Field01, Field02,...Field20. (I have
named fields [sic] on that way for the better explanation). <<

A column is not a field -- nothing like it at all. Since each column
is a separate attribute of the entity in your data model, it would be
VERY unusual to have such a table if you had a proper data model.

However, if I were writing a 1950's file system (files are made of
records which do have fields), then they would probably be a repeating
group -- and a violation of First Normal Form (1NF).

>> Now, suppose that we want to do almost the same update on all of the
fields [sic]: <<

In SQL an UPDATE works on entire rows (rows are not records), changing
all the columns at the same time.

UPDATE Foobar
SET x = <value1>,
y = <value2>,
z = <value3>,
etc.

If you want to pass the values as parameters, then you can skip some of
them by passing a NULL and having this SET clause in your UPDATE
statement.

SET x = COALESCE (<value1>, x)

Dynamic SQL generation is considered very poor design; it says you have
no data model and no idea what to do until run time.

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