Wise Owl Training - SQL blogs (page 1 of 4)

Using MERGE and MATCHED in SQL

Posted by Sam Lowrie on 21 June 2018

Learn how to MERGE rows from two tables into one combined table, and how to remove unwanted data from both tables.

Did you know there was an IIF function in SQL to test conditions? We didn't!

Posted by Andy Brown on 16 February 2018

You can use the IIF function in SQL as an alternative to the CASE WHEN statement. We thought we would share this new (for us) discovery with the world!

Create your own snippets of SQL code, and insert them into your queries

Posted by Andy Brown on 23 November 2017

With SQL Server 2012 came the power not just to use pre-defined code snippets, but also to create your own - this blog explains how.

Speed comparison of temporary tables against table variables

Posted by Andy Brown on 02 March 2017

When you are programming in SQL, you often have the choice of using table variables or temporary tables. This blog considers whether one method is substantially quicker than the other (spoiler alert: not really).

A list of one owl's 5 favourite system stored procedures in SQL!

Posted by Andy Brown on 03 February 2017

Everyone has a favourite system stored procedure (you do, don't you?). But five? That's the subject of this blog, anyway.

Wise Owl coding standards for T-SQL (the SQL dialect used in SQL Server)

Posted by Andy Brown on 01 February 2017

A blog setting out an approach to coding in SQL to ensure consistently high standards across your organisation.

Is the new(ish) FORMAT function in SQL Server slow?

Posted by Andy Brown on 16 January 2017

SQL Server 2012 saw the introduction of the T-SQL FORMAT function, making it easier to present dates nicely (no more remembering CONVERT arguments such as 103!). But is it too slow to be really useful? This blog aims to test this scientifically.

How to use the FOR XML keywords in SQL to concatenate ids

Posted by Andy Brown on 27 September 2016

If you want to group items in a SQL query, showing a comma-delimited list of ids for each, generating an XML file is not the obvious place to start - but it should be.

In SSMS, how to add multiple aliases to tables using the ALT key

Posted by Andy Brown on 23 March 2016

It's only a small thing, but … this blog shows how you can click and drag with the ALT key held down, then type to apply a table alias to lots of tables simultaneously.

Common Table Expressions are even better than I'd realised, as this blog shows

Posted by Andy Brown on 01 February 2016

CTEs (or Common Table Expressions) allow you to divide complicated queries up into two or more simple discrete tasks, as this blog explains.

A short blog listing many ways to create aliases for columns in SQL

Posted by Andy Brown on 01 February 2016

It's not often that this owl learns new things about SQL when giving a course, but when I do, I like to share my new knowledge! This blog shows a new way to create aliases for columns in SQL.

Pivoting Data in SQL Server

Posted by Andrew Gould on 09 June 2014

Using the Pivot operator in SQL Server allows you to create basic pivot tables from your query results. This blog teaches you how to create simple, static pivots, crosstab-style tables and exciting, dynamic pivot tables.

Triggers in SQL Server

Posted by Andrew Gould on 27 November 2013

Triggers are special stored procedures that execute automatically in response to certain events in a database. This blog explains how to create three types of trigger in SQL Server: DML, DDL and Logon triggers.

Transactions in SQL Server

Posted by Andrew Gould on 11 October 2013

This blog examines how to use Transactions in Microsoft SQL Server to allow you to control when data changes are committed to the database. You'll also discover how you can rollback transactions, effectively giving you the chance to undo changes to your data.

How to use the LAG and LEAD functions included in SQL Server 2012

Posted by Andy Brown on 20 September 2013

SQL Server 2012 introduces new functions to find the previous or subsequent value for a row, without using a complicated self-join. This blog explains how to use LAG and LEAD, including partitioning row sets.

Wise Owl suggestions for new features for SQL Server Management Studio

Posted by Andy Brown on 09 September 2013

Writing SQL in Management Studio could, Wise Owl feel, be made a little easier: here are 10 practical suggestions for how!

How to debug T-SQL queries and stored procedures

Posted by Andy Brown on 06 June 2013

This blog gives the low-down on how to start and use the debugger included in SQL Server Management Studio 2008 R2 and SSMS 2012.

Deleting and Updating Records in SQL

Posted by Andrew Gould on 08 May 2013

This blog teaches you how to modify existing data in your database by either deleting records or updating them.

How error messages work in SQL (including TRY, CATCH, RAISERROR and THROW)

Posted by Andy Brown on 03 May 2013

You can use BEGIN TRY to trap errors from SQL Server 2005 onwards, and also raise your own errors using RAISERROR or THROW - this blog explains all!

Using OUTER and CROSS APPLY joins to link to table-valued functions

Posted by Andy Brown on 03 May 2013

For the sake of completeness, this blog explains how to join to the results of table-valued functions (like a correlated subquery on steroids).