Blogs from Wise Owl on SQL Tutorial in T-SQL (page 1 of 3)

Showing blogs 1-20 (out of 41)

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.

Tags:   SQL | Triggers    |    T-SQL | SQL Tutorial

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.

Tags:   SQL | Transactions    |    T-SQL | SQL Tutorial

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.

Tags:   SQL | Errors, debugging    |    T-SQL | SQL Tutorial

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.

Tags:   SQL | Transactions    |    T-SQL | SQL Tutorial

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!

Tags:   SQL | Errors, debugging    |    T-SQL | SQL Tutorial

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).

Tags:   SQL | Joins    |    SQL | Functions    |    T-SQL | SQL Tutorial

Output Parameters and Return Codes in SQL Server

Posted by Andrew Gould on 26 April 2013

This blog teaches you how to return values from your SQL stored procedures using two different techniques: return codes, and output parameters.

Tags:   SQL | Stored procedures    |    T-SQL | SQL Tutorial

Dynamic SQL

Posted by Andrew Gould on 22 April 2013

Dynamic SQL is a technique for building valid SQL statements from separate pieces of text. You can use this technique to create remarkably flexible and useful queries, as long as you're aware of the potential danger of SQL injection attacks.

Tags:   SQL | Dynamic SQL    |    T-SQL | SQL Tutorial

Derived Tables in SQL

Posted by Andrew Gould on 08 April 2013

A derived table is a technique for creating a temporary set of records which can be used within another query in SQL. You can use derived tables to shorten long queries, or even just to break a complex process into logical steps.

Tags:   SQL | CTEs, subqueries    |    T-SQL | SQL Tutorial

Using Cursors in SQL Server

Posted by Andrew Gould on 26 March 2013

Cursors allow you to step through a set of data one record at a time. They’re not the quickest tool in SQL Server’s box, but they have their uses and this blog explains how they work.

Tags:   SQL | Cursors    |    T-SQL | SQL Tutorial

Loops in SQL

Posted by Andrew Gould on 18 February 2013

Many programming languages feature a variety of types of loop which allow your programs to repeat a set of instructions multiple times. In SQL there is only one type of loop, and this blog explains how it works!

Tags:   SQL | SQL programming    |    T-SQL | SQL Tutorial

Inline and multi-statement table-valued functions

Posted by Andy Brown on 08 February 2013

This blog shows you how to create table-valued functions in SQL (ie functions which return a table of data!).

Tags:   SQL | Programming tables    |    T-SQL | SQL Tutorial

How to create and use table variables in T-SQL

Posted by Andy Brown on 08 February 2013

Table variables allow you to hold rows of data in temporary storage, without any processing overhead. Read this blog to add this technique to your SQL armoury!

Tags:   SQL | Programming tables    |    T-SQL | SQL Tutorial

Exporting data from SQL Server Management Studio

Posted by Andrew Gould on 04 February 2013

While SQL Server Management Studio is a powerful tool for writing queries, it has absolutely no concessions towards making the results of those queries remotely presentable! This blog describes several techniques for getting the results of a query into another application so that you can format them to your heart’s content.

Tags:   SQL | General    |    T-SQL | SQL Tutorial

Scalar User Defined Functions in SQL Server - UDFs

Posted by Andrew Gould on 01 February 2013

If you have a calculation that you frequently use in SQL queries you're probably bored of writing out the same code time after time. Why not try creating a user-defined function to save you the hassle? This blog teaches you how to define your own custom functions, including how to use input parameters, how to alter a function after you've created it, and even how to use fancy programming techniques such as variables and IF statements to help structure complex sequences of calculations.

Tags:   SQL | Functions    |    T-SQL | SQL Tutorial

Writing IF and ELSE conditions in SQL

Posted by Andy Brown on 29 January 2013

You can use the IF statement to test conditions in SQL - this blog explains how, and also explains why you might prefer to use CASE WHEN instead.

Tags:   SQL | SQL programming    |    T-SQL | SQL Tutorial

SQL subqueries (including correlated subqueries)

Posted by Andrew Gould on 28 January 2013

If you’ve been writing SQL queries for a while you’re probably fairly confident with writing single SELECT statements to return a set of records. If you’re ready for a bit more of a challenge, this blog will teach you how to nest one SELECT statement inside another in order to create a subquery. If you’re thinking “that sounds simple enough” then you might want to read to the end of this series, where we’ll attempt to melt your brain by explaining correlated subqueries!

Tags:   SQL | CTEs, subqueries    |    T-SQL | SQL Tutorial

Using @@rowcount and other global variables

Posted by Andy Brown on 28 January 2013

SQL comes complete with a few useful global variables, giving you information such as the row number of the record just inserted, or the number of rows affected by a query. Here's how to use them!

Tags:   SQL | SQL programming    |    T-SQL | SQL Tutorial

Using Criteria in SQL Queries

Posted by Andrew Gould on 16 January 2013

When you write queries in SQL it's immensely useful to be able to show records matching criteria that you've set. You can do this using the WHERE clause and this blog teaches you how to use it!

Tags:   SQL | WHERE criteria    |    T-SQL | SQL Tutorial

Declaring and using SQL variables

Posted by Andy Brown on 03 January 2013

Variables in SQL always begin with @, and allow you to program more efficiently. Learn the tips and tricks in this short series of blogs!

Tags:   SQL | SQL programming    |    T-SQL | SQL Tutorial
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