HANA Beginner - some points that can help you for HA300 course/certification - Part 1
I have compiled herewith a few points that might help a person who is doing a HA300 - HANA Modelling course.
Personally when I did the training it took me a while to understand these concepts.
So try reading these points while you are at the course or just before attending one.
(Referring to Coll. 2014 SP8 release. The figure numbers referred here might change, but most likely the description of the figure will not, so you will be able to place it in revised collection materials)
Understanding the SQL/Table Joins:
1. While doing the course I found it slightly easier to understand the concepts namely - Left Join, Inner Join, Outer Join, Referential Join etc. with 1 dimension table and 1 fact table only.
I also later found this link on SCN All about Joins using SQL in HANA that simplifies the concept by using only 1 dimension and 1 fact table.
Note - the course uses 2 dimension table and 1 fact table.
The reason 1 and 1 helps is because it easily helps us to visualize a Left and Right join much faster this way.
Ofcourse after understanding the concept you should move to the example on the course.
2. Why is fact table considered to be on the left of a Join? - If you are creating an Attribute view, analytic or calculation view, the fact table is considered to be the left table by default.
Explicitly the reason for this is not mentioned in the book. However with a little bit of thinking it becomes very clear.
a. There should be a standard. Like the moving traffic drives on the right or left of the road always. This standard helps us to take it for granted that a vehicle will only approach through the right or left as is the rule in the country.
b. Most scenarios want to put a business sense to the measures and key figures. Hence you need to combine the fact with the Characteristics or Dimension table to put more intelligence in the report. So, whenever we do a join we need to have a measure available in the fact table. If we do a join we are intending to get only result whenever there is a measure available in the fact table.
Flipside - Imagine if you had a customer on the Customer dimension table and on the left of the join and he never made any business transaction with the company. If we do a join we will get the customer on the table with a Null value for the transaction field. We do not need this information.
Hope this explains why the fact table is considered on the left.
Do the Exercises for Sure:
The exercises are brilliant in the course material. Take your time and do the exercises. Your instructor should be able to import the folder content from WTS local to the "Resources Perspective". Go step by step on every exercise. Do not skip the exercise as the initial ones build the tables and views that need to be further consumed in the coming exercises. I have experienced personally and received feedback from a participant who attended the course a second time that the one differentiating factor in understanding the concept clearly in the second training is because he spent time in doing all the exercises.
Come back later sessions:
Unit 1 - Fig: 5 General Modeling Principles, Fig 6: Choose the Right Information Model.
When you first study the course do not break your head to undestand these figures. Skip it completely and go to the rest of the course. Once you are finished with the Calculation Views chapter, come back and read this and it will be like a breeze.
Unit 2 - Star Join, Union - Connecting Tables. Skip it and come back later.
a. Remember that the analytic views will put the fact table on the left though it appears to be in the center of a star or other joins.
b. Make note that "Derived Views" will have a difference in the HANA studio Modeller perspective as in - they cannot be edited. You will also see a message on the view.
c. Copy is similar to Derived only in the sense that the content of a copy immediately at the time of copying will be same but Copy remains mutually exclusive to the parent view from which the copy is made whereas the Derived one remains just a reflection of the parent view. You cannot edit anything in the Derived view, but Copy you will be able to rename or make changes.
_SYS_REPO is related to privileges and _SYS_BIC is related to Procedures:
You should get this one by yourself. But helps to know because you will have questions on this one for your certification exam.
When you do this chapter, do not miss the beautiful integration of excel with the HANA studio through the MDX. You have to create the hierarchy and then use MS Excel and import the data into it. Then put it on a pivot table and view the hierarchy. That gives you a very good understanding of the whole purpose of Modelling in HANA in addition to seeing the integration between the two. Outside of the WTS you may get a HANA studio and do most of the things in the exercises but this integration is hard to get. So do not miss this exercise.
When you do the exercise in the course you may not fully understand this.
1. You need to mandatory create a Schema with title "TCUR" under the Catalog folder.
2. Include the following tables as it is by title. If there is change in the title Currency Conversion will not work.
TCURC, TCURF, TCURN, TCURR, TCURT, TCURV, TCURW, TCURX.
3. Clearly check with the customer to give you the inputs of each of these tables as is used by them in their Organization and import them into HANA.
4. Once you have done the exercise with the "Input Parameters" to select the specific currency on which your output data needs to come, do try to define a new parameter like "Date". So you will have 2 input parameters.
When you try to get the output, you will first be prompted to enter the currency you want and then prompted to enter the date for which the conversion rate has to be picked. This step will help you to reinforce your idea regarding the "Input Parameters"
SAP HANA Academy for Sure!!!!:
Always remember that SAP HANA Academy channel on youtube is one of the most awesome resources you will ever get after finishing the session. Do not spend time on this channel before the course if you intend to do the course. Strictly go by the contents of the course and later go to the youtube to see some good sessions there.
P. S :
I will continuously update this document in case I found more points that can be helpful. If you think you can contribute to enrich this document, ask for a change or rephrase anywhere, please do leave a comment.