Explain EXPLAIN PIPELINE (children 3)
 Set
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 2)
    ExpressionList (children 1)
     Function count (children 1)
      ExpressionList (children 1)
       Identifier ID
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier t1
 Identifier Null
