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MS SQL Syntax

Posted on 2013-12-03
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Last Modified: 2013-12-04
I am trying to delete orphan records where the parent has been deleted (there is no FK defined).

This works:

select * from tblBVMeterReadingErrors a where not exists (Select 0 from tblBVMeterReadings b
where a.BV_Meter_Reading_ID = b.BV_Meter_Reading_ID);

But this doesn't:

delete from tblBVMeterReadingErrors a where not exists (Select 0 from tblBVMeterReadings b
where a.BV_Meter_Reading_ID = b.BV_Meter_Reading_ID);

What is wrong please?
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Question by:slimguy
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6 Comments
 
LVL 15

Expert Comment

by:gplana
ID: 39693901
Try this way:

delete from tblBVMeterReadingErrors where BV_Meter_Reading_ID NOT IN (Select BV_Meter_Reading_ID from tblBVMeterReadings
where b.BV_Meter_Reading_ID IS NOT NULL);

Open in new window

0
 
LVL 15

Accepted Solution

by:
gplana earned 100 total points
ID: 39693905
Sorry, I made a mistake: please remove the b.  from my previous solution:

delete from tblBVMeterReadingErrors where BV_Meter_Reading_ID NOT IN (Select BV_Meter_Reading_ID from tblBVMeterReadings
where BV_Meter_Reading_ID IS NOT NULL);

Open in new window

0
 
LVL 6

Expert Comment

by:ButlerTechnology
ID: 39693906
Select * from tblBVMeterReadingErros 
where bv_meterReading_ID not in (Select bv_MeterReadingID from tblBVMeterReading)

Delete from tblBVMeterReadingErros 
where bv_meterReading_ID not in (Select bv_MeterReadingID from tblBVMeterReading)

Open in new window


The above code should work.
Tom
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LVL 15

Expert Comment

by:gplana
ID: 39693927
ButlerTechnology, this is exactly my solution. I just only  add a filter to avoid NULL values which some times could cause problems in comparisions inside the NOT IN.
0
 
LVL 9

Expert Comment

by:QuinnDex
ID: 39693943
this should do it for you check you are getting the correct results with the select before using the delete

select * from tblBVMeterReadingErrors where not in(Select 0 from tblBVMeterReadings
where tblBVMeterReadingErrors .BV_Meter_Reading_ID = tblBVMeterReadings.BV_Meter_Reading_ID);

Open in new window




delete from tblBVMeterReadingErrors where not in(Select 0 from tblBVMeterReadings
where tblBVMeterReadingErrors .BV_Meter_Reading_ID = tblBVMeterReadings.BV_Meter_Reading_ID);

Open in new window

0
 

Author Closing Comment

by:slimguy
ID: 39694870
Many thanks, I should have seen that myself - got a mental block last night!
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