How to Change the Data Type of a Column in Table by Using Kusto Query | Kusto Query Tutorial (KQL)

Topic: How to Change The Type of a Column in Table by Using Kusto Query Language.

 //Let's create sample table TotalSale and insert some data.  
 //.drop table TotalSale  
 .create table TotalSale (  
   id: int   
   ,SalePersonFName: string  
   ,SalePersonLName : string  
   ,ProductName : string  
   ,ItemsSold : int  
   ,SoldPrice :real  
   ,SoldDate: date  
   ,City : string  
   ,State : string  
   ,Country : string  
   ,Region : string  
   )  

      //Insert data  
       .ingest inline into table TotalSale <|  
 11,Tamara,Tony,Cell Phone,2,1200.50,2015-03-03,Frankfurt,Hesse,Germany,Europe  
 9,Petra,Henry,TV,10,5000.89,2015-04-08,Paris,Île-de-France,France,Europe  
 3,Christy,Ladson,TV,3,1600,2015-04-02,High Point,NC,USA,North America  
 7,Chirag,Patel,Cell Phone,5,1500,2015-06-23,AhmadAbad,Gujrat,India,Asia  


 //select data from table  
 TotalSale  

 // Let's say if we want to change the value of SoldPrice to int instead of real  
 //Syntax: .alter column ['Table'].['ColumnX'] type=string  
 .alter column TotalSale.SoldPrice type=int   

 //select data from table  
 TotalSale  
 // notice that the SoldPrice is blank for any history data.  
 // you can insert new data   
  .ingest inline into table TotalSale <|  
 100,Tamara,Tony,Cell Phone,2,1201,2015-03-03,Frankfurt,Hesse,Germany,Europe  
 900,Petra,Henry,TV,10,5001,2015-04-08,Paris,Île-de-France,France,Europe  
 //check the data  
 TotalSale  

 // How to keep the history data, as if we change the data type of column we are losing the data.  
 // we can make a copy of the table and then use union   

 //clear the table  
 .clear table TotalSale data  

      //Insert data  
       .ingest inline into table TotalSale <|  
 11,Tamara,Tony,Cell Phone,2,1200.50,2015-03-03,Frankfurt,Hesse,Germany,Europe  
 9,Petra,Henry,TV,10,5000.89,2015-04-08,Paris,Île-de-France,France,Europe  
 3,Christy,Ladson,TV,3,1600,2015-04-02,High Point,NC,USA,North America  
 7,Chirag,Patel,Cell Phone,5,1500,2015-06-23,AhmadAbad,Gujrat,India,Asia  

 //check the data in TotalSale  
 TotalSale  

 // let's create History Total Sale table  
 .create table H_TotalSale(  
   id: int   
   ,SalePersonFName: string  
   ,SalePersonLName : string  
   ,ProductName : string  
   ,ItemsSold : int  
   ,SoldPrice :real  
   ,SoldDate: date  
   ,City : string  
   ,State : string  
   ,Country : string  
   ,Region : string  
   )  

 //Check the data for TotalSale and H_TotalSale  
 TotalSale  
 H_TotalSale  
   // swap the TotalSale table to H_TotalSale  
 .rename tables H_TotalSale=TotalSale, TotalSale=H_TotalSale  

 //Check the data for TotalSale and H_TotalSale  
 TotalSale  
 H_TotalSale  

 // Change the data type of column  
 .alter column TotalSale.SoldPrice type=int  
 // let's insert new records in TotalSale  
  .ingest inline into table TotalSale <|  
 100,Tamara,Tony,Cell Phone,2,1201,2015-03-03,Frankfurt,Hesse,Germany,Europe  
 900,Petra,Henry,TV,10,5001,2015-04-08,Paris,Île-de-France,France,Europe  

 // Get History Data and new data  
 //Check the data for TotalSale and H_TotalSale  
 TotalSale  
 H_TotalSale  

 // You will be using Union to get old and new data  
 H_TotalSale  
 | union TotalSale  

Video Demo: How to Change the Data Type of a Column in Table by Using Kusto Query Language