Explain EXPLAIN QUERY TREE (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 4)
    ExpressionList (children 1)
     Function count (children 1)
      ExpressionList
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier t_constraints_where
    Function or (children 1)
     ExpressionList (children 3)
      Function equals (children 1)
       ExpressionList (children 2)
        Identifier b
        Literal UInt64_1
      Function less (children 1)
       ExpressionList (children 2)
        Identifier b
        Literal UInt64_18
      Function greater (children 1)
       ExpressionList (children 2)
        Identifier b
        Literal UInt64_5
    Set