Within Query Builder, the Select Tables for Query preview displays an "Unknown Rows" message when the Generate Row Count SQL is blank for ODBC-based Data Connectors.
This is caused by databases that do not have known rowcounts in table metadata. Having a value in the “Generate Row Count SQL” field in the ODBC data connector definition can serve as a workaround. Adding the below (or similar) to the Data Connector's > SQL field and saving the Data Connector's configuration will generate the row count as expected.
Function({schema, table}, Concat("SELECT count(*) FROM ", If(schema == "", "", "\!"" || schema || "\!"" || ".") , "\!"" || table || "\!"", ";"));
