Author : Gopal Krishna Ranjan


Gopal Krishna Ranjan

About Gopal Krishna Ranjan

Gopal has 8 years of industry experience in Software development. He has a head down experience in Data Science, Database, Data Warehouse, Big Data and cloud technologies and has implemented end to end solutions. He has extensively worked on SQL Server, Python, Hadoop, Hive, Spark, Azure, Machine Learning, and MSBI (SSAS, SSIS, and SSRS). He also has good experience in windows and web application development using ASP.Net and C#.

Python use case – Resampling time series data (Upsampling and downsampling) – SQL Server 2017

Resampling time series data in SQL Server using Python’s pandas library

In this post, we are going to learn how we can use the power of Python in SQL Server 2017 to resample time series data using Python’s pandas library. Sometimes, we get the sample data (observations) at a different frequency (higher or lower) than the required frequency level. In such kind of scenarios, we need to modify the frequency of the given samples as per the frequency of the required outcome. Modifying the frequency of time series data using T-SQL query becomes a tedious task especially when we need to perform upsampling as we need to generate more rows than what we have in the sample dataset. The Python’s pandas module has in-built capabilities for frequency conversion. With the help of pandas resample method, we can increase or decrease the time series observation frequencies with only few lines of … More


Tidy Data in Python – First Step in Data Science and Machine Learning

Most of the Data Science / Machine Learning projects follow the Pareto principle where we spend almost 80% of the time in data preparation and remaining 20% in choosing and training the appropriate ML model. Mostly, the datasets we get to create Machine Learning models are messy datasets and cannot be fitted into the model directly. We need to perform some data cleaning steps in order to get a dataset which then can be fitted into the model. We need to make sure that the data we are inputting into the model is a tidy data. Indeed, it is the first step in a Machine Learning / Data Science project. We may need to repeat the data cleaning process many times as we face new challenges and problems while cleaning the data. Data cleaning is one of the most important and time taking process a Data Scientist performs before … More


Conditional group by in SQL Server

In this post, we are going to learn how we can apply a conditional GROUP BY clause on a column, based on the values of another column. Assume that we have a table named tbl_EmpSaleDetail which contains the sales records for each employee. Let’s have a look at the table data.

In the above table, we have these columns:

EmpName – Stores the name of the employee

SaleDate – Date of sale

SaleAmount – Amount of the sale

IsActive – Indicates whether the employee is active or not.

Now, we need this output.

In this output, we can see that all the data of inactive employees have been aggregated to a single row labeled as “–Inactive Employees Sales–” (Highlighted in red). However, the sum of the sales of the active employees are aggregated individually. Before writing the conditional group by query, lets create the sample table … More


Python use case – Import data from excel to sql server table – SQL Server 2017

If we need to import data from an excel file into SQL Server, we can use these methods:

  1. SQL Server Import Export Wizard
  2. Create an SSIS package to read excel file and load data into a SQL Server table
  3. Use T-SQL OPENROWSET query
  4. Use the read_excel method of Python’s pandas library (Only available in SQL Server 2017 onwards)

In this post “Python use case – Import data from excel to sql server table – SQL Server 2017”, we are going to learn that how we can use the power of Python in SQL Server 2017 to read a given excel file in a SQL table directly. With the integration of Python in SQL Server 2017, we can use the pandas read_excel method to read a given excel file with lots of customizations in SQL Server.

Assume that we have an excel file named EmployeeList.xlsx as this. Click here to More


Python use case – Import zipped file without unzipping it in SSIS and SQL Server – SQL Server 2017

Import zipped CSV file without unzipping it in SSIS using SQL Server 2017

SQL Server Integration Services (SSIS) is one of the most popular ETL tools. It has many built-in components which can be used in order to automate the enterprise ETL(Extract, Transform, and Load). Also, if we need a customized component which is not available in SSIS, we can simply create it by writing our own piece of code in C# using Script Task or Script Component.

In this post, we are going to explore that how we can read and load a zipped CSV file in SQL Server without unzipping it using SSIS along with SQL Server 2017. Reading a zipped file directly (without unzipping it) will save some time required in order to write the text file on the physical disk and then reading it from there. As of now, we don’t have any built-in component in … More


Find and Delete all duplicate rows but keep one

In this post “Find and Delete all duplicate rows but keep one”, we are going to discuss that how we can find and delete all the duplicate rows of a table except one row. Assume that we have a table named tbl_sample which has four columns – EmpId, EmpName, Age, and City. This table has some duplicate data (in all the four columns) which needs to be deleted except the original one row. To demonstrate this, let’s create the dummy table with some sample data.

Here is the code to create the dummy table with sample data:

Let’s have a look at the table data now.

In above table, we can see that we have multiple duplicate rows for EmpId 1, 2, 3 and 4. To find the duplicate records from the above table, we can use this query. This query will output all the duplicate rows from the … More


Import CSV file into SQL Server using T-SQL query 3

Sometimes, we need to read an external CSV file using T-SQL query in SQL Server. Due to some functional limitations, we cannot use the import-export wizard functionality in such kinds of scenarios as we need the result set in the middle of the execution of the other queries. There, we can use the BULK INSERT SQL command which helps us to import a data file into SQL Server table directly.

Let’s have a look at the sample CSV file which we want to import into a SQL table. The CSV file is this.

To download the sample CSV file, click here. The above CSV file uses comma as a column delimiter and contains 6 columns which are:

PersonID – Stores the Id of the person.

FullName – Stores the full name of the person.

PreferredName – Stores the preferred name of the person.

SearchName – Stores the search name … More


Python use case – Dynamic UNPIVOT using pandas – SQL Server 2017 1

In this post, we are going to learn how we can leverage the power of Python’s pandas module in SQL Server 2017. pandas is an open source Python library providing data frame as data structure similar to the SQL table with the vectorized operation support for high performance. To know more about pandas, you can click here.

Let’s discuss the problem we face while using the SQL UNPIVOT clause especially when we have a large number of columns. We can use UNPIVOT clause in SQL Server to convert the columns as row values and normalize the output result set. To use the UNPIVOT command, we need to specify each column name as a fixed value while writing the T-SQL query. However, this becomes annoying if we need to specify a large number of columns in the UNPIVOT clause. Also, if the column names are not fixed (dynamic in nature), … More


Handling special characters in Hive (using encoding properties) 1

In case we are reading a text file in a Hive table which contains non-English characters and we are not using the appropriate text encoding, these non-English characters might be loaded as junk symbols (like boxes – �). To get these characters in their original form, we need to use the correct character encoding. In this post “Handling special characters in Hive (using encoding properties)“, we are going to learn that how we can read special characters in Hive using encoding properties available with TBLPROPERTIES clause.

To demonstrate it, we will be using a dummy text file which is in ANSI text encoding format and contains Spanish characters. Also, we will be using Microsoft Azure cloud platform to instantiate an on-demand HDInsight cluster that makes it easy to write Hive queries. We will upload the dummy text file to an Azure Data Lake Storage and then we will … More


Skip header and footer rows in Hive 1

In this post “Skip header and footer rows in Hive“, we are going to learn that how we can ignore few header and footer records in Hive without loading or reading these records in another table or in a view temporarily. If you want to read more about Hive, visit my post “Preserve Hive metastore in Azure HDInsight” which explains Hive QL in detail.

Skip header and footer records in Hive

We can ignore N number of rows from top and bottom from a text file without loading that file in Hive using TBLPROPERTIES clause. The TBLPROPERTIES clause provides various features which can be set as per our need. It can be used in this scenario to handle the files which are being generated with additional header and footer records. Let’s have a look at the below sample file:

Now assume that we are dealing with … More