Something like COALESCE for complicated query? - sql

Question

Suppose I have a table1:
column1|column2|state|
-------|-------|-----|
test1 | 2| 0|
test1 | 3| 0|
test1 | 1| 1|
test2 | 2| 1|
test2 | 1| 2|
I want to select (actually delete, but I use select for testing) all columns that don't have unique column1 and don't select (actually retain) only the rows that have:
state = 0 and smallest value in column2,
if no row with state = 0 exists, then the row with just smallest value in column2.
So the result if the select should be:
column1|column2|state|
-------|-------|-----|
test1 | 3| 0|
test1 | 1| 1|
test2 | 2| 1|
and the retained rows (in case of delete) should be:
column1|column2|state|
-------|-------|-----|
test1 | 2| 0|
test2 | 1| 2|
I tried to achieve it with following (which does not work):
SELECT * FROM table1 AS result1
WHERE
result1.column1 IN
(SELECT
result2.column1
FROM
table1 AS result2
WHERE /*part that works*/)
AND
result1.column2 >
(SELECT
min(result3.column2)
FROM
table1 AS result3
WHERE (COALESCE(
result3.column1 = result1.column1
AND
result3.state = 0,
WHERE
result3.column1 = result1.column1
)))
The part that I can't figure out is behind result1.column2 >.
I want to compare the result1.column2 with the result of
smallest value from result-set where it3.state = 0,
if 1. does not exist, then with smallest value from similar result-set without it3.state = 0 condition.
That is my problem, I hope it makes sense. Maybe it can be rewritten in a more efficient/neater way completely.
Can you help me to fix that query?

Answer 1

Is this what you want?
SELECT
*
FROM
table1 AS result1
WHERE
result1.column1 IN (SELECT result2.column1
FROM table1 AS result2
WHERE /*part that works*/)
AND result1.column2 > COALESCE( ( SELECT min(result3.column2)
FROM table1 AS result3
WHERE result3.column1 = result1.column1
AND result3.state = 0 )
,( SELECT min(result3.column2)
FROM table1 AS result3
WHERE result3.column1 = result1.column1 )
)
;