SQL Bridge Module

The SQL Bridge module is a robust and flexible tool to map between OPC data and Database data. Transaction Groups are the heart of the SQL Bridge module. Transaction groups configured through the Ignition Designer, are units of execution that perform actions such as, storing data historically, synchronizing database values to OPC, and loading recipe values.

Transaction Groups

Transaction groups are configured in the Ignition Designer. Each Transaction Group is associated with a table in a database Ignition is connected to, and is made up of one or more Items. The group will then execute at a specific interval of time, or on a user-defined schedule. Generally each execution will create a new row in the database table with a separate column for each Item in the group. However it is possible for some types of Transaction Groups to take values from the database and write to specific tags.

Additionally the Transaction Group can be configured to conditionally synchronize values by using a trigger. The trigger is evaluated every execution, and if the trigger condition is met, then synchronization will occur. If the trigger condition has not been met then the group will wait until the next execution to re-evaluate the trigger.

There are several types of Transaction Groups, and each offers different functionality. For example the Historical Group allows you to quickly configure a group that reads OPC data and push it to the database. While the additional flexibility of a Standard Group allows you take values from the database and write them to

Items

Each Item in the Transaction Group consists of several properties, but the key properties are the Value and Target Name.

  • Value: The Value can be a reference to an OPC value such as a tag in the Tag Browser. However you can instead use a direct OPC Item Path without having to create a tag in Ignition first. Additionally the Value can be derived using Ignition's Expression Language.

  • Target Name: In most cases the Target Name is a column on the database table the Transaction Group is associated with. However it is possible to have the Target Name 'Read-only'. When set to 'Read-only' the value of the item will not be tied to any columns in the database, but is still visible from the Transaction Group and can be used as a trigger.

Versions

There are two versions of SQL Bridge

  • SQL Bridge Limited: The limited version of SQL Bridge only allows the use of Historical Groups

  • SQL Bridge: This version allows access to all four types of groups: Historical, Standard, Block, and Stored Procedure groups.

Regardless of version there are no licensing limitations on the number of groups you can create.