Explain EXPLAIN (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 2)
    ExpressionList (children 2)
     Identifier c1
     Subquery (children 1)
      SelectWithUnionQuery (children 1)
       ExpressionList (children 1)
        SelectQuery (children 3)
         ExpressionList (children 1)
          Function max (children 1)
           ExpressionList (children 1)
            Identifier c3
         TablesInSelectQuery (children 1)
          TablesInSelectQueryElement (children 1)
           TableExpression (children 1)
            TableIdentifier a
         Function and (children 1)
          ExpressionList (children 4)
           Function equals (children 1)
            ExpressionList (children 2)
             Identifier a.c1
             Identifier b.c2
           Function equals (children 1)
            ExpressionList (children 2)
             Identifier b.c1
             Identifier b.c2
           Function equals (children 1)
            ExpressionList (children 2)
             Identifier b.c1
             Identifier b.c3
           Function equals (children 1)
            ExpressionList (children 2)
             Identifier b.c2
             Identifier b.c4
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier b
