Explain EXPLAIN SYNTAX (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 3)
    ExpressionList (children 6)
     Identifier ts (alias --a.ts)
     Identifier id (alias --a.id)
     Identifier id_b (alias --a.id_b)
     Identifier b.ts (alias --b.ts)
     Identifier b.id (alias --b.id)
     Identifier id_c (alias --b.id_c)
    TablesInSelectQuery (children 2)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       Subquery (alias a) (children 1)
        SelectWithUnionQuery (children 1)
         ExpressionList (children 1)
          SelectQuery (children 2)
           ExpressionList (children 3)
            Identifier ts
            Identifier id
            Identifier id_b
           TablesInSelectQuery (children 1)
            TablesInSelectQueryElement (children 1)
             TableExpression (children 1)
              TableIdentifier A
     TablesInSelectQueryElement (children 2)
      TableExpression (children 1)
       TableIdentifier B (alias b)
      TableJoin (children 1)
       Function equals (children 1)
        ExpressionList (children 2)
         Identifier --b.id
         Identifier --a.id_b
    Function lessOrEquals (children 1)
     ExpressionList (children 2)
      Identifier --a.ts
      Function toDateTime (children 1)
       ExpressionList (children 1)
        Literal \'1970-01-01 03:00:00\'