In this article, we will discover some best practices of T-SQL queries. Badly written queries can cause performance and I/O problems. For this reason, we should pay attention to keep some rules in our mind when writing T-SQL queries.
The OVER and PARTITION BY functions are both functions used to portion a results set according to specified criteria.
This article explains how these two functions can be used in conjunction to retrieve partitioned data in very specific ways.
In this post, I am going to talk about an issue I found while restoring a backup of CDC enabled database to a different SQL instance. You may receive a warning message that includes some information about the cause of the warning, which can help you to resolve the issue. (more…)
This article is an effort to dissect the output of the sp_spaceused stored procedure.
Understanding the database usage internals and the growth trends play a vital role in the defining the right sizing of the database. sp_spaceused is probably an administrator’s most widely-executed system stored procedure to find the disk space used by a database. This helps get a quick glimpse of the database usage. statistics. sp_spaceused is used to display the number of rows, the data size, index size, amount of used space, unused space by each object, and the unallocated size of the database. Although looking at the values given by sp_spaceused, one shouldn’t think of shrinking the database or data file or log file. Many a time, we are unaware of what we are doing. Many a time, we don’t know what would be the aftereffects of doing such resource intrinsic operations. The output of sp_spaceused tells us a lot about the current performance of the database. The unallocated column and the unused column tell us the free space left at the database and the table levels. (more…)
In this article, we will focus on real time operational analytics and how to apply this approach to an OLTP database. When we look at the traditional analytical model, we can see OLTP and analytic environments are separate structures. First of all, the traditional analytic model environments need to create ETL (Extract, Transform and Load) tasks. Because we need to transfer transactional data to the data warehouse. These types of architecture have some disadvantages. They are cost, complexity and data latency. In order to eliminate these disadvantages, we need a different approach. (more…)
The SQL Server trigger is a special type of stored procedures that is automatically executed when an event occurs in a specific database server. SQL Server provides us with two main types of triggers: the DML Triggers and the DDL triggers. The DDL triggers will be fired in response to different Data Definition Language (DDL) events, such as executing CREATE, ALTER, DROP, GRANT, DENY, and REVOKE T-SQL statements. The DDL trigger can respond to the DDL actions by preventing these changes from affecting the database, perform another action in response to these DDL actions or recording these changes that are executed against the database. (more…)
This article will be interesting to those who often have to deal with data integration.
Assume that there is a database where users always modify data (update or remove). Perhaps, this database is used by a large application that does not allow modifying the table structure. The task is to load data from this database to another database on a different server from time to time. The simplest way to tackle the problem is to load the new data from a source database to a target database with preliminary cleaning up the target database. You can use this method as long as the time to load data is acceptable and does not exceed preset deadlines. What if it takes several days to load data? In addition, unstable communication channels lead to the situation when data load stops and restarts. If you face these obstacles, I suggest considering one of the ‘data reloading’ algorithms. It means that only data modifications occurred since the latest load are loaded.
Dynamic SQL and stored procedures are two of the most important components of SQL Server. In this article, we will look at the advantages and disadvantages of each of them and when to use them. (more…)
In this article, we will discuss how different types of indexes in SQL Server memory-optimized tables affect performance. We will examine examples of how different index types can affect the performance of memory-optimized tables.
To make the topic discussion easier, we will make use of a rather large example. For the purposes of simplicity, this example will feature different replicas of a single table, against which we will run different queries. These replicas will use different indexes, or no indexes at all (except, of course, the primary keys – PKs).
Note, that the actual purpose of this article is not to compare performance between disk-based and memory-optimized tables in SQL Server per se. Its purpose is to examine how indexes affect performance in memory-optimized tables. However, in order to have a full picture of the experiments, timings are also provided for the corresponding disk-based table queries and the speedups are calculated using the most optimal configuration of disk-based tables as baselines.
There is often a need to create a performance indicator that would show database activity related to the previous period or specific day. In the article titled “Implementing SQL Server Performance Indicator for Queries, Stored Procedures, and Triggers”, we provided an example of implementing this indicator.
In this article, we are going to describe another simple way to track how and how long the query execution takes, as well as how to retrieve execution plans for each time point.
This method is especially useful in the cases when you need to generate daily reports, so you can not only automate the method but also add it to the report with minimum technical details.
In this article, we will explore an example of implementing this common performance indicator where Total Elapsed Time will serve as a metric.