SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 3)
   ExpressionList (children 2)
    Identifier total_bytes
    Identifier total_rows
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier system.tables
   Function and (children 1)
    ExpressionList (children 2)
     Function equals (children 1)
      ExpressionList (children 2)
       Identifier database
       Function currentDatabase (children 1)
        ExpressionList
     Function equals (children 1)
      ExpressionList (children 2)
       Identifier name
       Literal \'check_system_tables\'
