Window function

Bollinger Bands in T-SQL

Bollinger Bands® is a technical analysis tool trademarked by its inventor, John Bollinger. The basis for the bands is a simple moving average (SMA). Standard deviation lines are calculated above and under this moving average. Those lines are the Bollinger Bands.

The bands illustrate volatility, since they move apart when there are large movments (volatility) in a stock price, and they move together when there are small movements. The stock price movements within these bands are then used as indicators in trading.

This blog post will show how to calculate Bollinger Bands in T-SQL. This calculation will only work on SQL Server 2012 and later.

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Weighted moving average in T-SQL

In an earlier post I demonstrated the calculation of moving averages in T-SQL. However, the there is one major drawback with simple moving averages. Price changes in the beginning of the period have the same importance as more recent price changes. Somehow you’d like to assign different weights to the price changes, so that the most recent changes gets the most weight.

For this purpose, a Weighted Moving Average (WMA) can be calculated. In this blog post I will show two different methods to calculate WMA, one that can be used on SQL Server 2005 and later, and the other version is for SQL Server versions earlier than 2005.

Weights WMA9
Weights WMA9

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Moving average in T-SQL

A common calculation in trend analysis is the moving (or rolling) average. A moving average is the average of the, for instance, last 10 rows. The moving average shows a more smooth curve than the actual values, more so with a longer period for the moving average, making it an good tool for trend analysis. This blog post will show how to calculate moving average in T-SQL. Different methods will be used depending on the version of SQL Server.

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