Explain EXPLAIN QUERY TREE (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 3)
    ExpressionList (children 1)
     Asterisk
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier 02668_logical_optimizer
    Function and (children 1)
     ExpressionList (children 2)
      Function equals (children 1)
       ExpressionList (children 2)
        Identifier a
        Literal UInt64_1
      Function equals (children 1)
       ExpressionList (children 2)
        Literal UInt64_2
        Identifier a
