Database Reference
In-Depth Information
OEQ3. Evolution of a dimension
table name and an attribute name could change in
some DW versions. In this case, equivalent tables
and attributes are taken into consideration. Since
the VERSION FROM clause was omitted, the
query will address all existing DW versions.
The general syntax of the query is shown below.
For a specified dimension that follows keyword
DIMENSION, the evolution of a specified hier-
archy is retrieved. The name of hierarchy whose
evolution history is to be retrieved follows key-
word HIERARCHY.
SHOW EVOLUTION OF
ATTRIBUTE amount
FROM FACT TABLE Sales
IN VERSION 'R_February'
SHOW EVOLUTION OF
DIMENSION dimension_name
HIERARCHY hierarchy_name
IN VERSION version_name
[VERSION FROM start_date
[TO end_date]]
OEQ2. Evolution of a fact or dimension
level table
The general syntax of the query is shown below.
The name of a fact or a level table whose evolution
is to be retrieved follows the FACT TABLE and
LEVEL TABLE keywords, respectively.
For example, the below query retrieves the
evolution of hierarchy H_product belonging to
dimension Product in base version R_March .
The evolution history is retrieved in all DW ver-
sions since the VERSION FROM clause was
not specified. Dimensions and hierarchies that
changed their names in some DW versions and
that are equivalent to H_product and Product are
also considered by the query.
SHOW EVOLUTION OF
{LEVEL|FACT} TABLE table_name
IN VERSION version_name
[VERSION FROM start_date
[TO end_date]]
For example, the below query retrieves the
evolution of a level table whose name is Shops
in base version R_April . The history of evolution
is retrieved from DW versions whose valid-
ity times are within the specified range in the
VERSION FROM ... TO ... clause. Similarly as
in the above queries, level tables (in other DW
versions) equivalent to Shops are also considered
by the query.
SHOW EVOLUTION OF
DIMENSION Product
HIERARCHY H_product
IN VERSION 'R_March'
OEQ4. Evolution of a
dimension instance
The general syntax of the query is shown below.
Similarly as in the query of type VQ5 , a dimen-
sion instance is specified by means of attribute
values belonging to levels. A dimension name
follows keyword DIMENSION. A dimension
instance is specified in clause INSTANCE OF
STRUCTURE.
SHOW EVOLUTION OF
LEVEL TABLE Shops
IN VERSION 'R_April'
VERSION FROM '01-01-2004'
TO '30-05-2004'
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