Posts by

Phil Factor

Phil Factor (real name withheld to protect the guilty), aka Database Mole, has 30 years of experience with database-intensive applications.

Despite having once been shouted at by a furious Bill Gates at an exhibition in the early 1980s, he has remained resolutely anonymous throughout his career.

He is a regular contributor to Simple Talk and SQLServerCentral.

Phil Factor

25 May 2018

5 Comments

Phil Factor

25 May 2018

5 Comments

Building reusable table build scripts using SQL Prompt

You’ve been working on a query, function or procedure and you want to store the results of executing it in a table; maybe a table variable, or a temporary table. These all require column definitions, and such things can be tiresome to do. Consider the following AdventureWorks query. Listing 1 You need to store... Read more

Phil Factor

18 May 2018

Phil Factor

18 May 2018

Finding code smells using SQL Prompt: TOP without ORDER BY in a SELECT statement

Using TOP in a SELECT statement without a subsequent ORDER BY clause is legal in SQL Server, but meaningless because asking for the TOP 10 rows implies that the data is guaranteed to be in a certain order, and tables have no implicit logical order. You must specify the order. In a SELECT statement,... Read more

Phil Factor

11 May 2018

1 Comment

Phil Factor

11 May 2018

1 Comment

Choosing Between Table Variables and Temporary Tables

People can, and do, argue a great deal about the relative merits of table variables and temporary tables. Sometimes, as when writing functions, you have no choice; but when you do you’ll find that both have their uses, and it’s easy to find examples where either one is quicker. In this article, I’ll explain... Read more

Phil Factor

2 May 2018

Phil Factor

2 May 2018

Pseudonymizing your data with SQL Data Generator

Imagine that you are the CIO of AdventureWorks. Out of a blue sky comes an order from Taxman that you supply details of all your sales, along with the tax charged to your customers. They want to be able to check that the total tax you pass on to them is correct, and is... Read more

Phil Factor

25 April 2018

Phil Factor

25 April 2018

Masking Data in Practice

Even small extracts of data need to be created with caution, if they are for public consumption. Sensitive data can 'hide' in unexpected places, and apparently innocuous data can be combined with other information to expose information about identifiable individuals. If we need to deliver an entire database in obfuscated form, the problems can... Read more

Phil Factor

18 April 2018

4 Comments

Phil Factor

18 April 2018

4 Comments

Avoid use of the MONEY and SMALLMONEY datatypes

The MONEY data type confuses the storage of data values with their display, though its name clearly suggests the sort of data it holds. It is proprietary to SQL Server and allows you to specify monetary values preceded by a currency symbol, but SQL Server doesn’t store any currency information at all with the... Read more

Phil Factor

12 April 2018

Phil Factor

12 April 2018

Custom Metrics for Detecting Problems with Ad-hoc Queries

Whatever development methodology you use, you must check on the quality of the code before releasing a version of a database. This isn’t just a general check for ‘technical debt’ or code smells; you must also make sure that queries are not hogging resources on the server. A common crime is the unnecessary overuse... Read more

Phil Factor

19 March 2018

3 Comments

Phil Factor

19 March 2018

3 Comments

When to use the SELECT…INTO statement

We can use SELECT…INTO in SQL Server to create a new table from a table source. SQL Server uses the attributes of the expressions in the SELECT list to define the structure of the new table. Prior to SQL Server 2005, use of SELECT…INTO in production code was a performance ‘code smell’ because it... Read more

Phil Factor

8 March 2018

1 Comment

Phil Factor

8 March 2018

1 Comment

Investigating problems with ad-hoc queries using SQL Monitor

There is nothing wrong with the principle of using ad-hoc queries; one can use them occasionally and perfectly legitimately. However, when ad-hoc queries run as part of a processes that does database operations iteratively, row-by-agonizing-row, they can be one of the most unremitting ways of sapping the performance of a SQL Server instance. You... Read more

Phil Factor

1 March 2018

6 Comments

Phil Factor

1 March 2018

6 Comments

Consider using [NOT] EXISTS instead of [NOT] IN (subquery)

It used to be that the EXISTS logical operator was faster than IN, when comparing data sets using a subquery. For example, in cases where the query had to perform a certain task, but only if the subquery returned any rows, then when evaluating WHERE EXISTS (subquery), the database engine could quit searching... Read more

Posts by Phil Factor

Posts by

Phil Factor