Skip to main content

SQL Server 70-461 Exams fundamental - Part 1 (Tips from Querying from Microsoft SQL Server Training kit by Itzik-Ben-Gan)

Hello Everybody!!! This time, it is about Microsoft Exam.
When I decided to take up Microsoft certification (MCSA) on Business Intelligence 2012 (I was planning from 3 years but was never that serious to write, Lol!! But now I am ready), I came up with training kit by Itzik-Ben-Gan. This book was very helpful for understanding the fundamentals of T-SQL and its architectures.

However, for my preparation standpoint view, I am summarizing the tips and points from the book which I believe, going through main points, will help lot of them to get small tips instead of reading entire book before day of exam. So let’s start with SQL….!!!

Standard SQL is based on the relational model, which is a mathematical model for data management and manipulations.
The word relational is not about 2 tables related but it is from mathematical concept of Set Relation from “Set theory”.

Relation in the relational model is called a “Table”. (T-SQL is based on multiset theory than on set theory).
For a table to be in Relational format, set of rules are applicable but if not followed, those tables are not really called relational or in other words, the so called relational table deviates from mathematical Set theory. The examples of such deviations are below.

For a table to be in Relational format, set of rules are applicable but if not followed, those tables are not really called relational or in other words, the so called relational table deviates from mathematical Set theory. The examples of such deviations are below.

Ø  Set theory say, A Set cannot have duplicates. This is not true when it comes to Table. T-SQL on querying a set of records, by default will not remove duplicates.
Ø  Adding DISTINCT which remove duplicates will make the table relational.
Ø  Set theory doesn’t believe in order of tuples (sets like a,b,c,z,y) arranged. T-SQL on enforcing the rules like ORDER BY clause, will make the table not relational or deviates from relational model.
(Note: SQL Server doesn’t track the order of records been saved into its memory. It randomly picks the location and no guarantee that SQL Server would save the data on particular address. The SQL Server stores the rows in a volatile fashion).
Ø  According to Relational theory, all the attributes should have names. It deviates in T-SQL where we still can write queries like,
Select EmpID, Firstname+ ‘  ‘ +LastName From Emp.
Where 2nd column resulting is derived column from Firstname and LastName but have no doesn’t have any name.
This can be overcome by;
 Select EmpID, Firstname+ ‘  ‘ +LastName as Name From Emp.
Ø  Same name of column cannot be a output if it is relational. Example ;
Select E1.ID  , E2.ID from … can result in column ID from 2 tables but this is not going to form relational table under relational model. Each column should be identify distinctly.
Ø  Set theory stands for 2 valued- logic (True or a False) but T-SQL is a three valued-logic system. It follows or predicates TRUE or FALSE OR UNKNOWN (NULL- Meaning missing value).
Ex: Select * From EMP Where Ename IS NULL.

Comments

Popular posts from this blog

BIG Data, Hadoop – Chapter 2 - Data Life Cycle

Data Life Cycle The data life cycle is pictorial defined as show below:     As we see, in our current system, we capture/ Extract our data, then we store it and later we process for reporting and analytics. But in case of big data, the problem lies in storing and then processing it faster. Hence Hadoop takes this portion, where it stores the data in effective format (Hadoop distributed File System) and also process using its engine (Map Reduce Engine). Since Map Reduce engine or Hadoop engine need data on HDFS format to process, We have favorable tools available in market to do this operation. As an example, Scoop is a tool which converts RDBMS to HDFS. Likewise we have SAP BOD to convert sap system data to HDFS.

OLE DB provider "Microsoft.ACE.OLEDB.12.0" for linked server "(null)" returned message "The Microsoft Access database engine cannot open or write to the file ''. It is already opened exclusively by another user, or you need permission to view and write its data.". Msg 7303, Level 16, State 1, Line 1 Cannot initialize the data source object of OLE DB provider "Microsoft.ACE.OLEDB.12.0" for linked server "(null)".

OLE DB provider "Microsoft.ACE.OLEDB.12.0" for linked server "(null)" returned message "The Microsoft Access database engine cannot open or write to the file ''. It is already opened exclusively by another user, or you need permission to view and write its data.". Msg 7303, Level 16, State 1, Line 1 Cannot initialize the data source object of OLE DB provider "Microsoft.ACE.OLEDB.12.0" for linked server "(null)". If you get this error while Loading Data From Excel to SQL Server, then, close the Excel sheet opened and try to run queries again.

Talend ETL Part 1: SQL Server Database to Excel Sheet

Hello All, Of many ETL tools available in Market, One of the strong tool is Talend. Difference between other ETL tools and tools like Pentaho, Talend, Clover ETL, Adeptia Integration etc, is that they support NO SQL Cross domains, BIG Data, Hadoop etc. Other ETL tools like, SSIS, Informatica are now coming with their higher versions, which consists of Hadoop Integration. Basically We can say, there are two databases types. 1) RDBMS (Example: SQL Server, MySQL, Oracle etc) 2) Non RDBMS (Example: MongoDB, InfiniDB etc) Talend Supports Non RDBMS databases. Here I would like to share my hands on experience on Talend and how to use it and explain basic components of Talend. Approx there are 500 components we can find in Talend. So lets Kick Start from Basics. First lets try to load Data from Microsoft SQL Server to Excel. Steps: Step1: Open Talend Studio. Step 2: Right click on Job Design and Create a new Job by giving some job name. Step 3: Give the name o...