The SELECT reserved word is part of the Data Manipulation Language (DML) defined by Codd and is used to query data from the database. Because of its popularity, there are many clauses and functions that can be used to construct a query to retrieve data. I am continuing our exploration by reviewing SELECT queries that aggregate data. Data aggregation is the process of converting many records into a few records with special meaning. I will be using the Adventure Works 2012 sample database supplied by Microsoft during this talk. Today,…
Month: December 2012
Summarizing Data – Part 1
The SELECT reserved word is part of the Data Manipulation Language (DML) defined by Codd and is used to query data from the database. Because of its popularity, there are many clauses and functions that can be used to construct a query to retrieve data. Today, I am continuing our exploration by reviewing SELECT queries that aggregate data. Data aggregation is the process of converting many records into a few records with special meaning. Many of the functions used in aggregation have statistical meaning such as minimum value, maximum value,…
Basic Training – Default Constraint
Today, I continuing my series of talks on fundamental SQL Server database topics. I am a proud United States Army Reservist (USAR) Veteran. Just like boot camp I went to so long ago, I am going nick name the series BASIC TRAINING. In my last article, I was talking about how to ADD, ALTER and DROP columns using the ALTER TABLE statement. One problem that we faced was how to add a column with a NOT NULL clause to an existing table that contained data. I will be introducing the…
Basic Training – Columns
Today, I continuing my series of talks on fundamental SQL Server database topics. I am a proud United States Army Reservist (USAR) Veteran. Just like boot camp I went to so long ago, I am going nick name the series BASIC TRAINING. The most basic part of a database is a TABLE which consists of COLUMNS. Many databases are works in progress that never ends since business requirements change as the company ages. With that said, changing the structure of a table is not an uncommon DBA task. We are…
Basic Training – All About NULL
Today, I continuing my series of talks on fundamental SQL Server database topics. I am a proud United States Army Reservist (USAR) Veteran. Just like boot camp I went to so long ago, I am going nick name the series BASIC TRAINING. The most basic part of a database is a TABLE which consists of COLUMNS. After choosing the data type for the COLUMN, we need to decide if the value is optional for some of the data rows. If it is, we need to define the column as NULL,…
Basic Training – Tables
Today, I continuing my series of talks on fundamental SQL Server database topics. I am a proud United States Army Reservist (USAR) Veteran. Just like boot camp I went to so long ago, I am going nick name the series BASIC TRAINING. The most basic part of a database is a TABLE which consists of COLUMNS. A important decision during the initial design is to choose the data types that will capture the information you want in the least amount of space. I did a good job covering the various…
Monitoring Database File Size
A Microsoft SQL Server database is composed of at least two operating system files: a primary data file (*.mdf) and a transaction log file (*.ldf). There might even be several secondary data files (*.ndf) if you have a Crafty database administrator (DBA) on staff. Today, we are going to talk about how these files grow and how they can be monitored. The strength of Microsoft SQL Server is the ease in which an accidental DBA can setup a database system in mere minutes. This same feature can be it’s downfall…
Monitoring Database VLF’s
The transaction log file records all transactions and the database modifications made by each connection. Heavy application processing against the database can make the transaction log grow quickly. Each physical log file is divided into smaller logical units called virtual log files (VLFs). If there is no auto-growth setting on the log file, the database will stop working, be marked as suspect, when you run out of space. Therefore, it is important to monitor database file space, both data and log, so this does not happen. I will present a…
Check Database Integrity Task
Today, I will be continuing the series of articles on the control flow tasks available in SQL Server Integration Services (SSIS) to perform Database Administration (DBA) tasks. We will be designing a SSIS package that checks the database integrity of all the user databases. I am going to start up SQL Server Data Tools (SSDT) which leverages the Visual Studio 2010 shell. This development environment replace the older Business Intelligence Development Studio (BIDS) which was released with SQL Server 2005. I will create a project named “check-database-integrity” under the “c:\ssis-depot\”…
Identity Column Insert
Today, I want to talk about how to insert a value into a identity column. Most of the time, the auto increment or IDENTITY column will just be happy by being left alone. Very seldom, a power user does something stupid like turn off the foreign key constraint and remove a key from a reference table. How do we add back the key? I will be dusting off the [WILDLIFE] database from a prior article. This database has one table named [ANIMALS]. It has 445 unique animal names each with…