Databases Reference
In-Depth Information
TABLE 5.2
Properties of
DataItem
Name (DDL)
Description
Defines the rules for comparing strings of text data. Collation
determines whether two text values are equal or different from
each other, and how they should be ordered. For example,
Collation
could specify whether to ignore case in determining
if two strings of text are the same or different.
Collation
Defines the rules for processing
NULL
data.
NullProcessing
can be set to one of five values:
NullProcessing
If you set it to
Preserv
e, Analysis Services preserves the
NULL
value.
Preserve
takes additional resources to store and
process
NULL
data. (We look at the question of the resources
required for
Preserve
in more detail when we discuss the physi-
cal data model in Chapter 20, “The Physical Data Model.”)
If you set it to
ZeroOrBlank
, Analysis Services converts the
NULL
value to 0 if the data type is not a string, and to a blank if
the data type is a string.
If you set it to
Unknown Member
, the
NULL
value is associated
with an unknown member.
If you set it to
Error
, the
NULL
value is not allowed and the
server will show an error message.
If you set it to
Automatic
, the server will choose the best value,
depending on the context.
Defines the rules for deleting trailing spaces at the beginning
and end of text. You can use
Trimming
to avoid the repetition of
two strings of text that differ only by leading or trailing spaces.
Trimming
Defines the rules of processing invalid XML characters. This
property is useful if you think your users will receive data in XML
format. In those cases, you can use
InvalidXmlCharacters
,
with one of three possible values:
Preserve
, which doesn't
change the character;
Remove
, which removes the characters
from the text; or
Replace
, which replaces each invalid character
with a question mark.
InvalidXmlCharacters
Listing 5.4 shows the DDL definition of a composite key, which uses
DataItem
s.
LISTING 5.4
DDL Definition of a Composite Key
<KeyColumns>
<KeyColumn>
<DataType>WChar</DataType>
<DataSize>50</DataSize>
<Source>
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