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Messages 1 to 3 of 3 total |
NULL as column in SELECT |
Wed, Aug 13 2014 3:40 AM | Permanent Link |
Roy Lambert NLH Associates Team Elevate | I would like to be able to use null as a constant in sql eg
SELECT CAST(_xTime AS VARCHAR(5) TIME FORMAT 'hh:mm') AS _Time, CAST(_xDate AS VARCHAR(10) DATE FORMAT 'DD/MM/YYYY') AS _Date, _TestPoint AS _Point, _mmolPL AS _Blood, _Comments AS _Comments, _Meds FROM BloodTests LEFT OUTER JOIN Medication ON Medication._fkBloodTests = _ID UNION SELECT null AS _Time, _Date AS _Date, null AS _Point, _HbA1c AS _Blood, null AS _Comments FROM HbA1c There will be another 4 tables included in the final expression many of which do not have equivalent columns so null is a better substitution than '' Roy Lambert |
Wed, Aug 13 2014 8:00 AM | Permanent Link |
Uli Becker | Roy,
> I would like to be able to use null as a constant in sql eg you can do that by casting the null value, e.g.: SELECT CAST(null as INTEGER) as test, test2 FROM mytable Uli |
Wed, Aug 13 2014 8:49 AM | Permanent Link |
Roy Lambert NLH Associates Team Elevate | Uli
Thanks, that will move me forward, and, as always is the case, now you suggest it I have seen it before but I'd forgotten it. It does raise an interesting question in my mind. Given the definition of null why should you have to cast it as a specific datatype? Unless its the first statement in the UNION then the parser already knows what the type should be, and objects if any subsequent ones are in error. Even though this is an acceptable workround I'd still like to be able to just use NULL without casting. Roy Lambert |
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