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 ?