also your format has to be consistent if you use PARSENAME otherways results can be unexpected
for example if you've just abcd_1234 it wont work
if you can atleast guarantee that you want part from first _ then you can do this
SELECT LEFT(STUFF(field,1,CHARINDEX('_',field),''),CHARINDEX('_',STUFF(field,1,CHARINDEX('_',field),'')+'_')-1)
FROM table
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SQL Server MVP
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