This course will help prep you to earn the CompTIA Healthcare IT Technician certification showing that you have the knowledge and skills needed to succeed in installing, managing, and troubleshooting IT systems in medical and clinical settings.
How to use complicated nested case statements?
I have a SQL statement to calculate some stats data for analytical report purpose, it's working good:
select
SUM(CASE WHEN (createDate = CURRENT_DATE AND exitDate IS NULL) THEN 1 ELSE 0 END)
...
from sample table
group by ...
Now I want to add more complicated logic to the script (adding nested "AND" and "OR" logic), something like:
select
SUM(CASE WHEN (createDate = CURRENT_DATE) AND (exitDate IS NULL OR (exitDate > CURRENT_DATE)) THEN 1 ELSE 0 END) AS survey_Tasks_Started_And_N
...
from sample table
group by...
The purpose is, when createDate = CURRENT_DATE, I want to include records of both (exitDate field is null) or (exitDate is later than today)
But seems it's not working if I add too many parenthesis and nested statements... Any solution for this kind of issue when adding complicated nested case statements in MySQL?
Or is there any recommendation for better solution for such common scenarios since too many nested level cause issue too?
Thanks!
select
SUM(CASE WHEN (createDate = CURRENT_DATE AND exitDate IS NULL) THEN 1 ELSE 0 END)
...
from sample table
group by ...
Now I want to add more complicated logic to the script (adding nested "AND" and "OR" logic), something like:
select
SUM(CASE WHEN (createDate = CURRENT_DATE) AND (exitDate IS NULL OR (exitDate > CURRENT_DATE)) THEN 1 ELSE 0 END) AS survey_Tasks_Started_And_N
...
from sample table
group by...
The purpose is, when createDate = CURRENT_DATE, I want to include records of both (exitDate field is null) or (exitDate is later than today)
But seems it's not working if I add too many parenthesis and nested statements... Any solution for this kind of issue when adding complicated nested case statements in MySQL?
Or is there any recommendation for better solution for such common scenarios since too many nested level cause issue too?
Thanks!
Who is Participating?
No reason that I know of for that not to work, of you post the actual query, and the results that suggest its not working and maybe someone can help further.
When my stuff gets complex I use CTE to clean it up.
With stuff as (
Select
(case when blah and blah then 1) as startedandnotcompleted from sampletable
)
Select count(*) from stuff where startedandnotcompleted = 1
With stuff as (
Select
(case when blah and blah then 1) as startedandnotcompleted from sampletable
)
Select count(*) from stuff where startedandnotcompleted = 1
Thanks, any further suggestion on the best practice to deal with such complicated nested scenario? I think it's very error-prone. Thanks.
There's nothing wrong with using complex/nested case statements, its a perfectly good solution to the right problem. All SQL is error prone - its very easy to get a query that works without giving you the data you want. Please post you query and the incorrect result as its not really possible to help you further in a general sense.
Question has a verified solution.
Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.
Have a better answer? Share it in a comment.
All Courses
From novice to tech pro — start learning today.
SUM(CASE WHEN createDate = CURRENT_DATE AND exitDate IS NULL THEN 1
WHEN createDate = CURRENT_DATE AND exitDate > CURRENT_DATE THEN 1
ELSE 0
END) AS survey_Tasks_Started_And_N
...
Note - when using case like this, it is always best to list the condition most likely to occur first, second most second, etc.