I want to handle if condition or case on join column in mysql query

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select m.Main_Test_Name,sum(datediff(s.job_submit_date,s.job_assign_date))/count(s.Sample_Details_Id) as averagetimetocompleteTest from main_test m inner join sample_details s on m.Main_Test_Id=s.Main_Test_Id group by m.Main_Test_Id;

my query is working fine (but in some cases i have insert date of

job_assign_date

as

'0001-01-01 00:00:00'

same for

job_submit_date '0001-01-01 00:00:00'

but when thes dates are

'0001-01-01 00:00:00'

then i want set it as null

but it gives me error

What I have tried:

I have tried

as 1)

select m.Main_Test_Name,sum(datediff(s.job_submit_date , case job_submit_date when '0001-01-01 00:00:00' then null else s.job_submit_date,s.job_assign_date))/count(s.Sample_Details_Id) as averagetimetocompleteTest from main_test m inner join sample_details s on m.Main_Test_Id=s.Main_Test_Id group by m.Main_Test_Id;";

2)

select m.Main_Test_Name,sum(datediff(s.job_submit_date,if(s.job_assign_date='0001-01-01 00:00:00',null,s.job_assign_date) s.job_assign_date)/count(s.Sample_Details_Id) as averagetimetocompleteTest from main_test m inner join sample_details s on m.Main_Test_Id=s.Main_Test_Id group by m.Main_Test_Id;

Posted 30-Oct-18 21:18pm

paul_vin

Updated 31-Oct-18 1:11am

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Comments

CHill60 31-Oct-18 5:44am

"but it gives me error" ... what error?
When posting questions to do with databases it is ALWAYS a good idea to share with us your table structure(s), some sample data and your expected results (for the data provided)

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Sandeep1003 · Accepted Answer · 2018-10-31T01:12:00

use

NULLIF

Returns a null value if the two specified expressions are equal. For example, SELECT NULLIF(4,4) AS Same, NULLIF(5,7) AS Different; returns NULL for the first column (4 and 4) because the two input values are the same. The second column returns the first value (5) because the two input values are different.

Syntax


NULLIF ( expression , expression )