The XAO Data Center's TAP end point. The Table Access Protocol (TAP) lets you execute queries against our database tables, inspect various metadata, and upload your own data. It is thus the VO's premier way to access public data holdings.

Tables exposed through this endpoint include: fast_pul from the fast_pul schema, dr3lite, edr3lite from the gaia schema, notf from the gallery schema, columns, services, tables from the glots schema, liujun from the liujun schema, nsone from the nsone schema, data from the obscode schema, main from the ppmxl schema, pulsar from the pul schema, data from the pulsarcatalog schema, main from the spm4 schema, columns, groups, key_columns, keys, schemas, tables from the tap_schema schema, data from the ucd schema, wugang from the wugang schema.

The Astronomical Data Query Language is the standard IVOA dialect of SQL; it contains a very general SELECT statement as well as some extensions for spherical geometry and higher mathematics.

returns the authority part of an ivoid (or, more generally a URI). So, ivo://org.gavo.dc/foo/bar#baz becomes org.gavo.dc.

The behaviour for anything that's not a full URI is undefined.

gavo_ipix returns the q3c ipix for a long/lat pair (it simply wraps the 13c_ang2ipix function).

This is probably only relevant when you play tricks with indices or PPMXL ids.

gavo_match returns 1 if the POSIX regular expression pattern matches anything in string, 0 otherwise.

returns the intersection of two MOCs.

returns the union of two MOCs.

The function returns a random number drawn from a normal distribution with mean mu and width sigma.

Implementation note: Right now, the Gaussian is approximated by summing up and scaling ten calls to random. This, hence, is not very precise or fast. It might work for some use cases, and we will provide a better implementation if this proves inadequate.

gavo_simbadpoint queries simbad for an identifier and returns the corresponding point. Note that identifier can only be a literal, i.e., as simple string rather than a column name. This is because our database cannot query simbad, and we probably wouldn't want to fire off millions of simbad queries anyway; use simbad's own TAP service for this kind of application.

returns the spectral value expr converted to dest_unit.

expr has to be in either energy, wavelength, or frequency, and dest_unit must be a VOUnit giving another spectral unit (e.g., MHz, keV, nm, or Angstrom). This is intended to let users express spectral constraints in their preferred unit independently of the choice of unit in the database. Examples::

gavo_specconv(obscore.em_min, "keV") > 300
gavo_specconv(obscore.em_max, "MHz") > 30
gavo_specconv(spectral_start, "Angstrom") > 4000

There is a variant of gavo_specconv accepting expr's unit in a third argument.

returns expr assumed to be in expr_unit expressed in dest_unit.

    This is a variant of the two-argument gavo_specconv for when
    the unit of expr is not known to the ADQL translator, either because
    it because it is a literal or because it does not look like
    a spectral unit.  Examples::

        gavo_specconv(656, 'nm', 'J') BETWEEN spectral_start AND spectral_end
        gavo_specconv(arccos(phi)*incidence, 'Hz', 'eV')

    Clearly, overriding known units is likely to yield bad results;
    the translator therefore warns if an existing unit is overridden
    with a different unit.

The function converts a postgres timestamp to julian date. This is naive; no corrections for timezones, let alone time scales or the like are done; you can thus not expect this to be good to second-precision unless you are careful in the construction of the timestamp.

The function converts a postgres timestamp to modified julian date. This is naive; no corrections for timezones, let alone time scales or the like are done; you can thus not expect this to be good to second-precision unless you are careful in the construction of the timestamp.

The function transforms ADQL geometries between various reference systems. geo can be a POINT, a CIRCLE, or a POLYGON, and the function will return a geometry of the same type. In the current implementation, from_sys and to_sys must be literal strings (i.e., they cannot be computed through expressions or be taken from database columns).

All transforms are just simple rotations, which is only a rough approximation to the actual relationships between reference systems (in particular between FK4 and ICRS-based ones). Note that, in particular, the epoch is not changed (i.e., no proper motions are applied).

We currently support the following reference frames: ICRS, FK5 (which is treated as ICRS), FK4 (for B1950. without epoch-dependent corrections), GALACTIC. Reference frame names are case-sensitive.

returns 1 if matchagainst is term or narrower in the IVOA vocabulary vocname, 0 otherwise.

This is intended for semantic querying. For instance, gavo_vocmatch('datalink/core', 'calibration', semantics) would be 1 if semantics is any of calibration, bias, dark, or flat.

For RDF-flavoured vocabularies (strict trees), term will expand to the entire branch rooted in term. For SKOS-flavoured vocabularies (where narrower is not transitive), only directly narrower terms will be included.

Both the term and the vocabulary name must be string literals (i.e., constants). matchagainst can be any string-valued expression.

The function takes two strings; the first is a list of words not containing the hash sign (#), concatenated by hash signs, the second is a word not containing the hash sign. It returns 1 if, compared case-insensitively, the second argument is in the list of words coded in the first argument. The behaviour in case the the second argument contains a hash sign is unspecified.

gavo_hasword returns 1 if needle shows up in haystack, 0 otherwise. This is for "google-like"-searches in text-like fields. In word, you can actually employ a fairly complex query language; see https://www.postgresql.org/docs/current/textsearch.html for details.

returns a POINT corresponding to the center of the healpix with the given index at the given order.

Returns the index of the (nest) healpix with order containing the spherical point (ra, dec).

An alternative, 2-argument form

ivo_healpix_index(order INTEGER, p POINT) -> BIGINT

is also available.

The aggregate function returns a histogram of val with nbins+2 elements. Assuming 0-based arrays, result[0] contains the number of underflows (i.e., val<lower), result[nbins+1] the number of overflows. Elements 1..nbins are the counts in nbins bins of width (upper-lower)/nbins. Clients will have to convert back to physical units using some external communication, there currently is no (meta-) data as lower and upper in the TAP response.

The function returns 1 if the interval iv contains val, 0 otherwise. The lower limit is always included in iv, behaviour on the upper limit is column-specific.

The function returns 1 if the interval [l1...h1] overlaps with the interval [l2...h2]. For the purposes of this function, the case l1=h2 or l2=h1 is treated as overlap. The function returns 0 for non-overlapping intervals.

ivo_nocasematch returns 1 if pattern matches value, 0 otherwise. pattern is defined as for the SQL LIKE operator, but the match is performed case-insensitively. This function in effect provides a surrogate for the ILIKE SQL operator that is missing from ADQL.

On this site, this is actually implemented using python's and SQL's LOWER, so for everything except ASCII, your mileage will vary.

An aggregate function returning all values of expression within a GROUP contcatenated with delimiter

Written after a table reference, TABLESAMPLE(10) will make the database only use 10% of the rows; these are `somewhat random' in that the system will use random blocks. This should be good enough when just testing queries (and much better than using TOP n).

A geometry function creating MOCs. It either takes a string argument with an ASCII MOC ('4/13 17-18 8/3002'), or an order and another geometry.

This is the standard SQL COALESCE for providing defaults in case of NULL values.

You can compute with vectors here. See https://wiki.ivoa.net/twiki/bin/view/IVOA/ADQLVectorMath for an overview of the functions and operators available.

The SQL92 CASE expression