Database design

Kimberly Killian

How to Split a Comma Separated Value (CSV) file into SQL Server Columns

December 29, 2016 by

Receiving a comma delimited file is not new technology nor is it difficult to deal with in SQL Server. As a matter of fact, it is extremely easy. There are many cases as to why you would want to do this. For example, you have an external data source that needs to be imported into your database/table. There a couple ways to do this, however the quickest and easiest way is to use the native “import” feature within SQL Server Management Studio and you can even save it to an SSIS Package at the end of the process. The end result of using this method is that the external CSV file is loaded into a SQL Server table where columns are created and rows are populated.

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Gerald Britton

Why is my CTE so slow?

December 22, 2016 by

Introduction

Have you ever written up a complex query using Common Table Expressions (CTEs) only to be disappointed by the performance? Have you been blaming the CTE? This article looks at that problem to show that it is a little deeper than a particular syntax choice and offers some tips on how to improve performance.

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Sifiso Ndlovu

Top 5 New SQL Server 2016 DMVs for DBAs

December 20, 2016 by

Since its initial release that was part of SQL Server 2005, Dynamic Management Views (DMV) changed – mostly for the better – the role of database administration (DBA) within SQL Server-based environments. They improved the efficiency of DBAs regarding database server monitoring, issue diagnoses, and subsequent performance optimisation. As a result of this positive reception, it has become customary that some of the highly anticipated items in every release of SQL Server includes discovering what new DMVs will be added. In this article I take you through my favourite top 5 DMVs to come out of SQL Server 2016.

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Ahmad Yaseen

Understanding the SQL Server Proportional fill algorithm

November 22, 2016 by

When creating a database, SQL Server maps this database with minimum two operating system files; the database data file MDF and the database log file LDF. Logically, the database data files are created under a collection set of files that simplifies the database administration, this logical file container is called the Filegroup. Database data files can come in two types, the Primary data files that contains metadata information for the database and pointers to the other database files in addition to the data, where each database should have only one Primary data file and the optional Secondary files to store data only. The basic storage unit in SQL Server is the Page, with each page size equal to 8KB. And each 8 pages with 64KB size called Extent.

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Ahmad Yaseen

SQL Server Partitioned Views

November 18, 2016 by

SQL Server table partitioning is a great feature that can be used to split large tables into multiple smaller tables, transparently. It allows you to store your data in many filegroups and keep the database files in different disk drives, with the ability to move the data in and out the partitioned tables easily. A common example for tables partitioning is archiving old data to slow disk drives and use the fast ones to store the frequently accessed data. Table partitioning improves query performance by excluding the partitions that are not needed in the result set. But table partitioning is available only in the Enterprise SQL Server Edition, which is not easy to upgrade to for most of small and medium companies due to its expensive license cost.

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Ahmad Yaseen

How to track the history of data changes using SQL Server 2016 System-Versioned Temporal Tables

September 23, 2016 by

SQL Server 2016 introduces a new type of table that is designed to keep the full history of data changes, where row validity is managed by the system. This new table type is called a System-Versioned Temporal Table. In earlier SQL Server versions, user tables would enable you to hold only the most recent copy of the row, without being able to query the value before the UPDATE or DELETE operations. Using a Temporal Table, you will be able to query the recent state of the row as usual, in addition to the ability to query the full history of that row, which is fully managed by the SQL Server Engine, as you can’t define the rows validity period explicitly.

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Ahmad Yaseen

Database checkpoints – Enhancements in SQL Server 2016

September 21, 2016 by

When a new row is inserted or an existing one is updated in your database, the SQL Server Database Engine will keep that change in the buffer pool in the memory first, without applying each change directly to the database files for IO performance reasons. These data pages located in the buffer pool and not reflected yet to the database files are called Dirty Pages. The SQL Server Database Engine uses a special kind of processes to write these dirty pages to the data and log database files periodically. These processes are called Checkpoints. The Checkpoint creates a mark that is used by the SQL Server Database Engine to redo any transaction that is committed, written to the database transaction log file without reflecting the data changes to the data files due to an unexpected shutdown or crash. Also, this recovery point that is created by the Checkpoint will be used to roll back any data changes associated with uncommitted transaction, by reversing the operation written in the transaction log file. In this way the SQL Server Engine will guarantee the database consistency. The time that is taken by the SQL Server Database Engine to redo and undo the transactions is called the Recovery Time. All information about the Checkpoints will be written to the database boot page to identify till which point the database files are synchronized with the buffer pool when the system wakes up after crash or shutdown.

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Ahmad Yaseen

Optimize NULL values storage consumption using SQL Server Sparse Columns

August 29, 2016 by

SQL Server 2008 introduces a new column attribute that is used to reduce the storage consumed by NULL values in the database tables. This feature is known as Sparse Columns. Sparse Columns work effectively in the case of the columns with high proportion of NULL values, as SQL Server will not consume any space storing the NULL values at all, which helps in optimizing the SQL storage usage.

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Brian Bønk Rueløkke

Ready, SET, go – How does SQL Server handle recursive CTE’s

August 19, 2016 by

First of all, a quick recap on what a recursive query is.

Recursive queries are useful when building hierarchies, traverse datasets and generate arbitrary rowsets etc. The recursive part (simply) means joining a rowset with itself an arbitrary number of times.

A recursive query is defined by an anchor set (the base rowset of the recursion) and a recursive part (the operation that should be done over the previous rowset).

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Jean-Pierre Voogt

The new SQL Server 2016 sample database

July 22, 2016 by

Background

We have all learned to love and hate the trusty Bike shop database. Almost every demo or presentation pertaining to SQL Server we do, we use the AdventureWorks sample database. Almost every code sample on books online references AdventureWorks for illustrations and practical explanations of a feature. When SQL Server 2005 was released Microsoft replaced the old Pubs & Northwind Sample databases with a more complete and more feature rich database called AdventureWorks. Ever since we have been using this new sample database for almost everything we want to test. Microsoft has now given us an even better sample database called WorldWideImporters, which utilises almost every SQL Server feature I can think of from Temporal Tables to In-Memory table.

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Ahmad Yaseen

SQL Server 2014 contained databases

June 1, 2016 by

SQL Server provides two ways to authenticate users; SQL Server Authentication, which requires a predefined username and password to connect to the SQL Server, and Windows Authentication, in which SQL Server trusts the windows integrated user. The server level user that is authenticated to connect to the SQL Server is called a Server Login. This login should be mapped to a database user and granted permissions at the database level in order to access the database and be able to perform the authorized tasks. The relationship between the Server login and the database user in addition to the database metadata stored in the master system database draw up the dependencies between the SQL Server databases the server-level resources.

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