Conditional Joins…I don’t see much about this topic in cyberspace, but I occasionally run into performance problems with them. So this posting is all about them…or more specifically about why you should avoid them. A conditional join is a join (either inner or outer, by the way) that contains an “either-or” condition, easily identified because… Continue reading Should I use an “OR” in a JOIN?
Many developers find this topic to be mysterious or confusing. Let’s try to shed some light on this subject. What is a transaction and how is it managed in the database? Why is my connection blocking others (my T-SQL statements completed hours ago)? Simply put, from Microsoft’s .NET website: “A transaction consists of a single… Continue reading SQL Server Transaction Management
What is a SQL Server execution plan? Big topic: I suggest grabbing Grant Fritchey’s book SQL Server Execution Plans (A free eBook at the time of this post); 332 pages of good stuff on execution plans. You can get it here: Redgate link to Fritchey’s eBook So you don’t want to read a whole book… Continue reading Execution Plan Basics
This is the story of my saga to get DTC working in a clustered environment. It’s a bit different from other postings that I read and tried so I thought it was worth posting… We have a “test” SQL Server instance and it was noted that DTC (Distributed Transaction Coordinator) was throwing errors. The users… Continue reading DTC – Why Doesn’t it work?
Tracking your backups…one of the most basic/mundane/important functions for which a DBA is usually responsible. How do you know that your databases are being successfully backed up? What about your transaction logs? If you don’t have a current backup (even for a development database!), you and your users could be “up the creek without a… Continue reading Tracking your Backups
The JOIN clause seems to frequently be a source of mystery/frustration/wonderment for developers, so today I decided provide some information that may demystify it for you. First, a quick definition: a JOIN allows you to retrieve data from 2 (or more) tables based on logical relationships between the tables. A JOIN allows you to retrieve… Continue reading Notes about JOIN
Generally speaking, most T-SQL queries contain WHERE clauses to filter out data and WHERE clauses almost always contain a reference to a column…after all, that’s why the WHERE clause exists (to filter out the data). However, occasionally there is a need to use a condition in a WHERE clause that has no reference to any… Continue reading WHERE Clauses Without Column References