Compare the same id with 2 values in string in one table - sql

Question

I have a table like this:
id
status
grade
123
Overall
A
123
Current
B
234
Overall
B
234
Current
D
345
Overall
C
345
Current
A
May I know how can I display how many ids is fitting with the condition:
The grade is sorted like this A > B > C > D > F,
and the Overall grade must be greater than or equal to the Current grade
Is it need to use CASE() to switch the grade to a number first?
e.g. A = 4, B = 3, C = 2, D = 1, F = 0
In the table, there should be 345 is not match the condition. How can I display the tables below:
qty_pass_the_condition
qty_fail_the_condition
total_ids
2
1
3
and\
fail_id
345
Thanks.

Answer 1

As grade is sequential you can do order by desc to make the number. for the first result you can do something like below
select
sum(case when GradeRankO >= GradeRankC then 1 else 0 end) AS
qty_pass_the_condition,
sum(case when GradeRankO < GradeRankC then 1 else 0 end) AS
qty_fail_the_condition,
count(*) AS total_ids
from
(
select * from (
select Id,Status,
Rank() over (partition by Id order by grade desc) GradeRankO
from YourTbale
) as a where Status='Overall'
) as b
inner join
(
select * from (
select Id,Status,
Rank() over (partition by Id order by grade desc) GradeRankC
from YourTbale
) as a where Status='Current'
) as c on b.Id=c.Id
For second one you can do below
select
b.Id fail_id
from
(
select * from (
select Id,Status,
Rank() over (partition by Id order by grade desc) GradeRankO
from Grade
) as a where Status='Overall'
) as b
inner join
(
select * from (
select Id,Status,
Rank() over (partition by Id order by grade desc) GradeRankC
from Grade
) as a where Status='Current'
) as c on b.Id=c.Id
where GradeRankO < GradeRankC

Answer 2

You can use pretty simple conditional aggregation for this, there is no need for window functions.
A Pass is when the row of Overall has grade which is less than or equal to Current, with "less than" being in A-Z order.
Then aggregate again over the whole table, and qty_pass_the_condition is simply the number of non-nulls in Pass. And qty_fail_the_condition is the inverse of that.
SELECT
qty_pass_the_condition = COUNT(t.Pass),
qty_fail_the_condition = COUNT(*) - COUNT(t.Pass),
total_ids = COUNT(*)
FROM (
SELECT
t.id,
Pass = CASE WHEN MIN(CASE WHEN t.status = 'Overall' THEN t.grade END) <=
MIN(CASE WHEN t.status = 'Current' THEN t.grade END)
THEN 1 END
FROM YourTable t
GROUP BY
t.id
) t;
To query the actual failed IDs, simply use a HAVING clause:
SELECT
t.id
FROM YourTable t
GROUP BY
t.id
HAVING MIN(CASE WHEN t.status = 'Overall' THEN t.grade END) >
MIN(CASE WHEN t.status = 'Current' THEN t.grade END);
db<>fiddle