SQL: update in order to remove characters after "_"

Hello experts,

I have the following query which allows me to identify the various lines with under_score:


SELECT Cardinality,
MSTTID,
SPOTID,
SPoTInternalID  FROM mstt_schema.SPOT_MSTT_MATCH
WHERE CHARINDEX('_' ,SPOTinternalID ) > 0

result:

Cardinality      MSTTID      SPOTID      SPoTInternalID
1-1      1BN6Q5F_20171112      1BN6Q5F_20171112      439378_20171112
1-1      1C236S2_20171112      1C236S2_20171112      574109_20171112
1-1      1CKL7AK_20171109      1CKL7AK_20171109      901162_20171109
1-1      1CKL8TV_20171109      1CKL8TV_20171109      901238_20171109

I am looking for an update query in order to remove all the characters which are after _

The expected result is the following:

Cardinality      MSTTID      SPOTID      SPoTInternalID
1-1      1BN6Q5F      1BN6Q5F      439378
1-1      1C236S2      1C236S2      574109
1-1      1CKL7AK      1CKL7AK      901162
1-1      1CKL8TV      1CKL8TV      901238

Thank you very much for your help.