SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 3)
   ExpressionList (children 1)
    Identifier a
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 2)
      TableIdentifier tab_00712_2
      SampleRatio 1 / 2
   Function equals (children 1)
    ExpressionList (children 2)
     Identifier b
     Literal UInt64_2