Discussion of article "Integrating MQL-based Expert Advisors and databases (SQL Server, .NET and C#)"

Questions related to integrating the work with databased into Expert Advisors written in MQL5 often appear on the forums. Interest in this topic is not surprising. Databases are very good as a means of saving data. Unlike the terminal logs, the data do not disappear from the databases. They are easy to sort and filter, choosing only the required ones. A database can be used to pass the necessary information to an expert — for example, certain commands. And most importantly — the obtained data can be analyzed from different perspectives and processed statistically. For example, writing a one-line query is enough to find out the average and total profit for a specified time for each currency pair. And now imagine how long it takes to manually calculate this for the account history in the trading terminal.

Unfortunately, MetaTrader does not provide built-in tools for interacting with database servers. The problem can only be solved by importing functions from DLL files. The task is not simple, but feasible.

Start the expert, changing the connection string values to your database server access parameters. If everything is done correctly, the expert will output the following to the log:

Connecting to the database, executing SQL commands, writing and reading data — everything is executed successfully.