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A few notes on A few notes on JVOQLJVOQL
François OchsenbeinFrançois Ochsenbein
JVOQL: a few questionsJVOQL: a few questions
FROM clause: not clear how to FROM clause: not clear how to specify the list e.g.specify the list e.g. catalogues from some author ? catalogues from some author ? catalogues covering some wavelength catalogues covering some wavelength
range ?range ? must the conditions be known by the must the conditions be known by the
registry ?registry ? Non-SQL examplesNon-SQL examples
create view as
select * from table1
where [not] exist table2
create view as
select * from table1
union select * from table2
UCD Usage in JVOQLUCD Usage in JVOQL UCDs enable the possibility of UCDs enable the possibility of genericgeneric
queries queries (column names are not known!)(column names are not known!) Give all objects having a V magnitude in a Give all objects having a V magnitude in a
rangerange Give all known quasars with redshift > 1Give all known quasars with redshift > 1
Used in Aladin for 'filtering' (graphical Used in Aladin for 'filtering' (graphical representation)representation) circles with radius proportionnal to circles with radius proportionnal to
brightnessbrightness draw ellipses from major/minor axises + PAdraw ellipses from major/minor axises + PA use a color function of use a color function of V-RV-R
But UCDs are But UCDs are not unique not unique !!
Several columns of a catalog may share the Several columns of a catalog may share the same UCDsame UCD
measurements at different epochsmeasurements at different epochs measurements coming from different origins measurements coming from different origins
(e.g. USNO-B1)(e.g. USNO-B1)
The default rule could be:The default rule could be:
-- Take the first column matching the UCD-- Take the first column matching the UCD
-- or better, take the first column -- or better, take the first column with not-null with not-null contentscontents
Questions about Questions about XMATCHXMATCH
XMATCH(a,b,...) < XMATCH(a,b,...) < somethingsomething Can the Can the somethingsomething be in the table be in the table
(e.g. 3sigmas) or some combination (e.g. 3sigmas) or some combination of the error ellipses ?of the error ellipses ?
limited to positional criteria ?limited to positional criteria ?
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