Skip to main content

USING CASE IN SELECT STATEMENT


USING CASE IN SELECT STATEMENT/ IMPLEMENT IF-THEN-ELSE LOGIC IN SELECT STATEMENT


With Example let us understand, How to use CASE Condition in SQL SELECT Statement.

I have table EMP having column EMPLOYEEID, MARITALSTATUS, GENDER.

Click on pic to enlarge view




































Say if we want to Display under following condition

  •  If MaritalStatus is M, Then display it as Married, If MaritalStatus is S, then display it as Single and Other than M or S, then Display it as Unknown.
  •  If Gender is M, Then display it as Male, If Gender is F, then display as Female and Other than M or F, then Display it as Unknown.


This can be achieved in many ways, for example using REPLACE Function etc, but since my intention is on CASE Statement, I will Continue to demonstrate it using CASE.

Let’s do it for Condition 1 first:

As per Condition 1, we can use CASE STATEMENT as Shown:

SELECT EMPLOYEEID
                    ,MARITALSTATUS
                    ,MARITALSTATUS_EXPN = CASE MARITALSTATUS
                                         WHEN 'M'
                                                             THEN 'MARRIED'
                                         WHEN 'S'
                                                             THEN 'SINGLE'
                                         ELSE 'UNKNOWN'
                                         END
FROM EMP

I’m using MARITALSTATUS_EXPN to display condition met column.

When MaritalStatus is M, then ‘Married’ is displayed and When MaritalStatus is S, ‘Single’ is displayed and anything other than this will be considered as UNKNOWN.

The result is of query is shown in below snippet:

Click on pic to enlarge view
































Similarly, we can write CASE statement for Second condition as shown below:


SELECT EMPLOYEEID
      ,GENDER
      ,GENDER_EXPN = CASE GENDER
            WHEN 'M'
                  THEN 'MALE'
            WHEN 'F'
                  THEN 'FEMALE'
            ELSE 'UNKNOWN'
            END
FROM EMP



Click on pic to enlarge view































Combining both the expression above to get result in single Query,

 
SELECT EMPLOYEEID
        ,GENDER
        ,GENDER_EXPN = CASE GENDER
               WHEN 'M'
                       THEN 'MALE'
               WHEN 'F'
                       THEN 'FEMALE'
               ELSE 'UNKNOWN'
               END
        ,MARITALSTATUS_EXPN = CASE MARITALSTATUS
               WHEN 'M'
                       THEN 'MARRIED'
               WHEN 'S'
                       THEN 'SINGLE'
               ELSE 'UNKNOWN'
               END
FROM EMP


Click on pic to enlarge view





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.

BIG Data, Hadoop – Chapter 1 - Understanding Big Data & Hadoop

Understanding Big Data We all in recent time, came across the word ‘Big Data’. So the question is what exactly is Big Data? How much TB or GB or data is called a Big Data? Well, there is no standard size definition for Big Data. If current system when not able to handle the data, then, we call such data as Big Data. (Big Data is just a terminology used in IT) As an example, if I take a text file of 50 GB, Processing a text file of 50 GB size on our Laptop or computer is not a huge task but if we take a smart phone, processing 10 GB of data is huge task. That means, for mobile phone, that 50 GB of data is Big Data. Understanding Hadoop Our current systems such as ETL tools, reporting tools, programming environment all have capability of handling few petabyte of Data. And the growth of data annually is shown below in chart And also the growth of unstructured, Semi structured data are increasingly every day. So there is a need of more adv...