将列添加到SQL查询结果中

I'm putting together a report in SSRS. The dataset is populated with a SQL query of an MS SQL server. It's querying several similar tables using Union All. The problem is that there's some information loss. The different tables are for different worksites, but none of the columns in those tables has the name of the site; the only way to identify a site is by the table name. In the combined columns which are the result of the Union All, there's no way to tell which rows come from which site.I'm putting together a report in SSRS. The data