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The SQL Bridge Module enables the creation of Transaction Groups that synchronize data between PLCs and databases. You can use Transaction Groups to easily log from PLCs to the database, move data from the database back to PLCs, and even keep the two synchronized. Drag and drop functionality makes setup of Transaction Groups quick and easy. 

Originally conceived as an easy data storage method, Transaction Groups have become a core feature of Ignition. In their simplest form, they regularly read values from OPC addresses and store them into a SQL database. While data collection is still their primary use, they have grown in functionality over time. 

To set up and use Transaction Groups, SQL knowledge is not required. Ignition can automatically create and manage the database table for each group. Prior experience writing SQL queries or creating database tables are not required to log data. 

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Types of Transaction Groups

There are four types of Transaction Groups, and they each handle data a little differently:

  • Historical Groups - Quick and easy group that collects historical records
  • Standard Groups - An improved version version of the historical group that can reverse the flow of data, writing database values directly to Tags. 
  • Block Group - Records "blocks" of data, allowing you to record multiple values per execution in a tall format. 
  • Stored Procedure Group - Invokes a stored procedure in the database, returning the results of any OUT or INOUT parameters to Tags.

Learn more about each type of group on the Understanding Transaction Groups page. 

All Transaction Groups can execute at a set rate or on a schedule. A trigger can be used to determine when the group should record. You can use Ignition's expression language in the trigger to allow complex logic to determine when logging occurs, making precision execution easy. 

Historical Data Logging

Historical Groups quickly and easily store data from the plant floor into any kind of SQL database. Items from any or all devices can be included in the same group, just drag a few Tags over and start the group running. Ignition will log the data until you tell it to stop.

Database and OPC Synchronization

Standard Groups are the most flexible group. They are capable of not only storing OPC values in the database, but can also write database values to OPC addresses or synchronize data changes between both the database and PLC. With this group you can create true realtime value tables in the database, and allow anything that can talk to the database to push values to a PLC. This is often used to create Recipe systems where the recipe values are stored in the database, and a user can select a recipe to write all your settings directly to Tags. Changing recipes is as easy as changing a Tag value or selecting a name.

Large Data Block Storage

Transfer large amounts of data very efficiently with the Block Group. This groups allows you to send whole arrays of data to and from the database. It works just like the Standard group, but on a much larger scale.

Stored Procedures

The Stored Procedure Group allows you to use PLC data as inputs and outputs for your existing Stored Procedures. With the Stored Procedure Group, your IT department can have control over how data is entered and returned from the database.

Centralizing Data Collection

In Distributed systems, PLCs can be spread out over great distances to remote sites. Collecting and centralizing data from each can be difficult and time consuming. To combat this problem, Transaction Groups are used as the cornerstone of our Hub and Spoke architecture. Historical Groups can be applied locally to each PLC for a minimal cost, and forward all data into a single, central, database.

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