Author: Ben Richardson

Ben Richardson runs Acuity Training. Acuity is an IT training business offering classroom courses in London and Guildford. It is a leading provider of SQL training the UK and offers a full range of SQL training from introductory training to advanced administration courses.

Applying SQL Transformations and Handling Missing Values in Azure ML

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In this article, we will introduce SQL transformations in action. We will also see how to handle missing values in our dataset.

Consider a scenario of a movie rating dataset containing records of different movies along with the average user ratings associated with each movie. The ratings are in numeric form ranging from 1 to 10 with 1 as the lowest rating and, respectively, 10 as the highest rating (though no movie in the history has achieved 10 rating:). Suppose that we want to convert the numeric ratings into categorical ratings. For instance, we want to replace ratings of 1-3 with the categorical value “poor”, of 4-6 with “average” while ratings of 7-10 will have the value “good”. We can accomplish it with SQL transformation in Azure ML Studio. Read More

Understanding SQL Server Always Encrypted

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Security is one of the most important requirements for a data-driven system. Encryption is one of the ways to secure the data. Wikipedia defines encryption as:

“Encryption is the process of encoding a message or information in such a way that only authorized parties can access it and those who are not authorized cannot.”

In SQL Server 2016, Microsoft introduced an encryption feature called Always Encrypted. In this article, we will see what Always Encrypted is, and how it can be used to encrypt and decrypt data, with the help of simple examples.

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Introduction to Row-Level Security in SQL Server

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Problem

Prior to SQL Server 2016, table-level security was the default lowest level of security for a database. In other words, a user could be restricted to access a table as a whole. However, in some cases we need users to have access to a table, but not to specific rows within the table. Prior to SQL Server 2016, this required custom stored procedures to be written for the provision of such fine-grained security. However, such stored procedures are prone to SQL injection and other security caveats.

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Passing Data Table as Parameter to Stored Procedures

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Real-world database applications need to make multiple requests from the front end to the database in order to carry out all sorts of functions.

If an application is data-intensive, such as the ones used in banks or airports, etc., the number of data trips can be huge. Each request to a database utilizes bandwidth and requires time to execute. Without the table-valued parameters, a front application needs to make multiple data trips in order to manipulate multiple rows of data. However, with table-valued parameters, multiple rows can be inserted, updated, and deleted from a database using a single parameterized command that takes a table-valued parameter. Read More

Implementing Paging Using OFFSET FETCH NEXT in SQL Server

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A database can have hundreds of thousands of records. It is easy to insert and select these records via database management systems like SQL Server or MySQL etc. However, it is not easy to display thousands of records on a single webpage or in a desktop application. Space and memory constraints make it difficult to display a huge number of records all at once.

A common solution to such a problem is to implement paging. (Note, this is not memory paging implemented by operating systems) Paging in programming refers to displaying data via a series of pages. A random Google search may result in thousands of results. Google uses paging to display these results. If you scroll down the Google page with search results you would see the following:

Here you can see the number of pages that the search result is divided into. You can click the Next link to see more pages.

In this article, we will see how OFFSET FETCH NEXT operators can be used to implement paging on front-end applications. We will begin with a simple example using the OFFSET FETCH NEXT operator and will then see how it can be practically used with the help of a stored procedure.

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Similarities and Differences among RANK, DENSE_RANK and ROW_NUMBER Functions

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The RANK, DENSE_RANK, and ROW_NUMBER functions are used to retrieve an increasing integer value. They start with a value based on the condition imposed by the ORDER BY clause. All of these functions require the ORDER BY clause to function properly. In the case of partitioned data, the integer counter is reset to 1 for each partition.

In this article, we will study the RANK, DENSE_RANK, and ROW_NUMBER functions in detail, but before that, let’s create dummy data that these functions can be used on unless your database is fully backed up. Read More

Understanding GROUPING and GROUPING_ID Functions in SQL Server

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The ROLLUP and CUBE operators are used to return results aggregated by the columns in the GROUP BY clause.

The GROUPING and GROUPING_ID functions are used to identify whether the columns in the GROUP BY list are aggregated (using the ROLLUP or CUBE operators) or not.

There are two major differences between the GROUPING and GROUPING_ID Functions.

They are as follows:

  • The GROUPING function is applicable on a single column, whereas the column list for the GROUPING_ID function has to match the column list in the GROUP BY clause.
  • The GROUPING function indicates whether a column in the GROUP BY list is aggregated or not. It returns 1 if the result set is aggregated, and 0 if the result set is not aggregated.

On the other hand, the GROUPING_ID function also returns an integer. However, it performs the binary to decimal conversion after concatenating the outcome of all of the GROUPING functions.

In this article, we will see the GROUPING and GROUPING_ID functions in action with the help of examples. Read More

Logon Triggers in SQL Server

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A logon trigger, as the name suggests, is a trigger that fires in response to a LOGON event in SQL Server.

In simple terms, a logon trigger fires whenever someone tries to establish a new connection to a database server. The trigger fires after the user authentication and the login phase completes but before the user session is actually initiated. Read More