UPDATE and return some rows twice - sql

Question

I try to update and return rows. The problem is I use a nested select with UNION to get some rows twice and I want to get them returned twice. Example:
Table:
First_name | last_name | ready
-----------+-----------+------
john | doe | false
| smith | false
jane | | false
Query:
With list(name) as (
Select First_name
from table1
where First_name Not null and ready=false
union
Select last_name
from table1
where last_name Not null and ready=false
)
Select * from list
This returns:
John
jane
doe
smith
Now I want to update the rows found by the select and use update ... returning instead. But the update only returns the three affected rows, while I want it to return the rows as the select in the example does. Is there any way?

Answer 1

Rewrite to:
WITH cte AS (
UPDATE table1
SET ready = true
WHERE (first_name IS NOT NULL OR last_name IS NOT NULL)
AND NOT ready
RETURNING first_name, last_name
)
SELECT first_name FROM cte WHERE first_name IS NOT NULL
UNION ALL
SELECT last_name FROM cte WHERE last_name IS NOT NULL;
Same result, just shorter and faster: This query accesses table1 a single time instead of three times like in your original.
(Verify the superior performance with EXPLAIN ANALYZE on a test table.)
UNION ALL like #Clodoaldo already mentioned. UNION would eliminate duplicates, which is substantially slower (and probably wrong here).

Answer 2

with list(name) as (
select first_name
from table1
where first_name is not null and ready=false
union all
select last_name
from table1
where last_name is not null and ready=false
), u as (
update table1
set ready = true
where
(first_name is not null or last_name is not null)
and
not ready
)
select * from list
You need union all to have the four rows. It is is [not] null