The MACD (Moving Average Converenge Divergence) is a calculation in technical analysis used as a indicator of strength in a trend, or momentum in a stocks closing prices. The calculation uses different lengths of EMA (I covered the calculation of EMA in an earlier blog post here).

The MACD calculation uses the difference between a long EMA and a short EMA to create a oscillator (usually EMA12 – EMA26). The term Moving Average Converenge Divergence comes from the converging and divergence of these two moving averages. When the two moves towards each other there is convergence, and when they move away from each other, there is divergence. A divergence is commonly interpreted as a sign that the current trend is ending.

The MACD also moves around a zero line and when the MACD is above the zero line, that is used as a indicator of upward momentum (higher closing prices) since the short term EMA is above the long term EMA. And of course, if MACD is below the zero line this is an indicator of downward momentum.

Image by Kevin Ryde
Image by Kevin Ryde. Green line is MACD, red line is EMA9 of MACD.
White histogram is the difference between the two.

Further, a EMA9 is calculated for the MACD. This line is called the “Signal line”. The signal line is used in a trigger for buy and sell signals. More specifically, traders look for crossovers of the two lines. When the MACD moves over the MACD:EMA9, this is a buy signal since it indicates a upward momentum (a bullish market) of the closing prices. And when the MACD crosses under the MACD:EMA9, this is a sell signal since this is a indicator of downward momentum (bearish market).

This blog post will show how to calculate MACD in T-SQL. It works on all versions of SQL Server.


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