Data blog — data comparison RSS



Assisted data comparison

Data comparison is an often overlooked problem that many IT professionals have to approach in their daily work. Without even realizing it, they spend a significant portion of their time comparing the data. In many cases the data comparisons are implemented ad-hoc: developers, QA testers or DBAs write SQL queries that return rows with differences between data sets. Often the data to compare do not reside in the same data store - they have to be pulled in to a location where it is possible to execute a query. This takes time. This takes mental effort. This creates opportunity for mistakes. It turns out that there are many data comparison tools, varying with their capabilities and price. These tools can...

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Data migration projects - why and how

Data migration reasons Sooner or later, if you are a database developer or a data architect, you will be faced with a data migration project. Data migrations are executed by organizations due to many different factors. The organizations try to avoid the data migrations, if they can, because in many cases it is a costly and complicated process. Optimally, a data driven application should work for many years without major changes, aside from only patching and updating their data store. Indeed, even upgrading a database version to a newer one can become quite a complicated project, well exceeding the backup-restore approach, so desired by the management and the development teams. Here is a few of many reasons why the migrations take place....

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Write Select Statements for Excel Spreadsheets

SelectCompare allows for data comparison of Excel spreadsheets, as well as other data sources with simple, unified interface. You may be initially anxious about writing an SQL statement to pull data from your Excel, but it is actually pretty easy! This post will show you a few examples of writing queries against your spreadsheet that you will be able to use right away for your Excel data comparison. If you want to find out how to connect to an Excel workbook, please read another post on this blog - Compare Excel Spreadsheets You will see below how to query Excel spreadsheets, specify ranges of columns and rows, and write simple filters that make SQL so powerful. In a general sense,...

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How to compare database schema with baseline

It is easy to create a comparison project to compare the schema of tables in a database and a saved baseline stored in Excel. After all, the database schema is stored in system views, and contains full information about your columns, data types, stored procedures and other elements of a typical database. For this post, I limited the schema information to the list of columns returned by the query  select * from information_schema.columns Note: This post uses SQL Server databases AdventureWorks2014 and AdventureWorks2008 databases as example environment, but you can connect any other database technology - MySQL, Oracle, MariaDB, PostgreSQL, and more! Create your data baseline I selected the columns information from AdventureWorks2008 and exported it to an Excel workbook using SelectCompare....

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SQL Data Comparison - User Manual

You visit this page because you know how to write a SQL query. Learn how you can use your expertise to do your work better and save your time! The Idea The SelectCompare idea is very simple: write an SQL query to extract data to compare on each data source. With SelectCompare, you create comparison projects that define data connections to each of the data sources and you write SQL queries for these data connections. You can create data connections separately from comparison projects, and reuse data connections in multiple projects. This is a quick manual that will show you how to compare data using SelectCompare. Step by step When you launch the program, you are presented with the page containing all defined comparison projects. Initially...

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