Difference between Identity & Sequence in SQL Server August 15, 2018 by Ben Richardson In SQL Server, both the SEQUENCE object and IDENTITY property are used to generate a sequence of numeric values in an ascending order. However, there are several differences between the IDENTITY property and SEQUENCE object. In this article, we will look at these differences. Read more »
Identifying Object Dependencies in SQL Server Management Studio July 16, 2018 by Ben Richardson In relational database systems, objects have different types of relationships with each other. Apart from table relationships (such as one to one, one to many and many to many), objects such as stored procedures, views, custom functions also have dependencies on other objects. It is important to understand object dependencies, particularly if you want to update an object that depends upon other objects. Read more »
The Difference between CROSS APPLY and OUTER APPLY in SQL Server June 6, 2018 by Ben Richardson SQL Server supports table valued functions, what are functions that return data in the form of tables. JOIN operations in SQL Server are used to join two or more tables. However, JOIN operations cannot be used to join a table with the output of a table valued function. APPLY operators are used for this purpose. Read more »
Understanding SQL Server’s TRY_PARSE and TRY_CONVERT functions May 16, 2018 by Ben Richardson Data conversion is one of the most fundamental tasks of any programming language. Data received from different sources is often not in the right format. For example, if you receive an XML file where age is in the string format and you want to calculate an average age for the people in the file you will need to convert age into an integer. To make the conversion process simple, the TRY_PARSE and TRY_CONVERT functions were introduced in SQL Server 2012. Before TRY_PARSE and TRY_CONVERT, SQL Server only had the PARSE and CONVERT functions. Read more »
Understanding the GUID data type in SQL Server May 3, 2018 by Ben Richardson What is a GUID? GUID is a 16 byte binary SQL Server data type that is globally unique across tables, databases, and servers. The term GUID stands for Globally Unique Identifier and it is used interchangeably with UNIQUEIDENTIFIER. Read more »
Sequence Objects in SQL Server March 22, 2018 by Ben Richardson Sequence objects are used to sequentially generate numeric values. They were introduced in SQL Server 2012. Sequence objects are similar to the IDENTITY column in any SQL table. However, unlike the IDENTITY column, they are independent and are not attached to any table. Sequence objects are used both independently and within the DML statements i.e. INSERT, UPDATE and DELETE. This article will take a detailed look at sequence objects. Read more »
Debugging stored procedures in SQL Server Management Studio (SSMS) February 20, 2018 by Ben Richardson Debugging is one of the most important but painful parts of any software process. To find some errors you have to run the code step by step to see which section of the code is responsible for the error. This is called runtime debugging. Luckily, SQL Server Management Studio (SSMS) comes with automated debugging capabilities to help developers debug their scripts. In this article, we will explain practically how SSMS can be used to debug stored procedures in SQL Server by working through a very simple example. Read more »
Understanding SQL Server query plan cache January 18, 2018 by Ben Richardson Whenever a query is run for the first time in SQL Server, it is compiled and a query plan is generated for the query. Every query requires a query plan before it is actually executed. This query plan is stored in SQL Server query plan cache. This way when that query is run again, SQL Server doesn’t need to create another query plan; rather it uses the cached query plan which improved database performance. The duration that a query plan stays in the plan cache depends upon how often a query is executed. Query plans that are used more often, stay in the query plan cache for longer durations, and vice-versa. Read more »
Understanding cursors and replacing them with JOINs in SQL Server November 24, 2017 by Ben Richardson Relational database management systems including SQL Server are very good at processing data in sets. However, if you want to process data on row-by-row basis rather than in sets, cursors are your only choice. Unfortunately, cursors are extremely slow and so where possible should be replaced with JOINS. Read more »
How SQL Server selects a deadlock victim October 20, 2017 by Ben Richardson In the article on Deadlock Analysis and Prevention, we saw how deadlock occurs. We saw that SQL Server selects one of the processes involved in the deadlock as deadlock victim. In this article, we will look at the criteria on which SQL server selects a deadlock victim. Why one process is selected as deadlock victim and not the other. Read more »
What is the difference between Clustered and Non-Clustered Indexes in SQL Server? August 28, 2017 by Ben Richardson Indexes are used to speed-up query process in SQL Server, resulting in high performance. They are similar to textbook indexes. In textbooks, if you need to go to a particular chapter, you go to the index, find the page number of the chapter and go directly to that page. Without indexes, the process of finding your desired chapter would have been very slow. Read more »
How to use SQL Server built-in functions and create user-defined scalar functions July 7, 2017 by Ben Richardson A function is a set of SQL statements that perform a specific task. Functions foster code reusability. If you have to repeatedly write large SQL scripts to perform the same task, you can create a function that performs that task. Next time instead of rewriting the SQL, you can simply call that function. A function accepts inputs in the form of parameters and returns a value. SQL Server comes with a set of built-in functions that perform a variety of tasks. Read more »
How to use Window functions in SQL Server June 9, 2017 by Ben Richardson All database users know about regular aggregate functions which operate on an entire table and are used with a GROUP BY clause. But very few people use Window functions in SQL. These operate on a set of rows and return a single aggregated value for each row. Read more »
