Creating the Date Dimension Using SQL and SAS to process dates.

Base E-R Diagram

Create DateSurrogates Index CREATE TABLE DateSurrogates (OrderDate Date CONSTRAINT pk PRIMARY KEY, Surrogate AUTOINCREMENT, DateKey Integer);

Create Date Key INSERT INTO DateSurrogates (OrderDate) SELECT DISTINCT OrderDate FROM OrdersCopy WHERE OrderDate NOT IN (SELECT OrderDate FROM DateSurrogates);

Update DateKey UPDATE DateSurrogates SET DateKey = Surrogate WHERE DateKey IS Null;

DateSurrogatesTable DateSurrogates: OrderDate Date/Time Surrogate Autoincrement DateKey Integer

Importing Into SAS PROC IMPORT OUT= WORK.CUSTOMER DATATABLE= "DateSurrogates“ DBMS=ACCESS2000 REPLACE; DATABASE="C:\DataWarehousing04s\ETL\PremiereExtractExample.mdb"; RUN;

Results of Proc Contents ----Alphabetic List of Variables and Attributes----- # Variable Type Len Pos Format Informat Label 3 DateKey Num 8 16 11. 11. DateKey 1 OrderDate Num 8 0 DATETIME20. DATETIME20. OrderDate 2 Surrogate Num 8 8 11. 11. Surrogate

SAS Date and Time Functions and Formats SAS has a number of useful functions for working with dates and times. Their options depend on the data type of the variable. DATETIME stores both the date and time DATE stores date information (in days from January 1, 1960) TIME stores time information (in seconds.fraction)

Functions Functions take values and convert the way the data is stored Function Use Datapart Takes a datetime attribute, extracts the date part and stores it as a date attribute Timepart Takes a datetime attribute, extracts the time part and stores it as a Time attribute

Functions Function Use Use Put(attribute, format) Input(attribute, informat) Use Returns a (character) value using a specified format. Returns the value produced when a SAS expression is read using a specified informat.

Formats and Informats Formats determine how a variable is displayed; informats determine how a variable id read. The tend to be similar. FORMATNAMEw.d Formats and Informats always contain a period (.) SAS makes assumptions about the best display for a given w.d specification

Some Useful Formats YEARw. MONNAMEw. DOWNAMEw. QTRw. JULDAYw. Writes date values as the year Writes date values as the quarter of the year Writes data values as the the name of the day of the week writes dates as the Julian day of the year (yyddd). For w=3 the output is ddd.