医学公开数据库查询与登记

references/sdss.md

Base URL

https://skyserver.sdss.org/dr18/SkyServerWS

Replace dr18 with the desired data release (e.g., dr17, dr16).

Authentication

No API key required. All endpoints are public.

Key Endpoints

1. SQL Search (CasJobs-style free-form SQL)

GET /SearchTools/SqlSearch

Parameter	Type	Description
cmd	string	Required. SQL query against the selected SkyServer release schema; this synchronous API is separate from asynchronous CasJobs.
format	string	json, xml, csv, html, votable. Default: html.

Example — query 10 galaxies:

https://skyserver.sdss.org/dr18/SkyServerWS/SearchTools/SqlSearch?cmd=SELECT TOP 10 objid,ra,dec,u,g,r,i,z FROM PhotoObj WHERE type=3&format=json

Type codes: 3 = galaxy, 6 = star.

Response (JSON, illustrative):

[
  {"Rows": [
    {"objid": 1237645941825863680, "ra": 195.123, "dec": 2.456, "u": 22.1, "g": 20.8, "r": 19.5, "i": 19.1, "z": 18.9}
  ]}
]

The response may contain a separate SqlQuery table alongside the result table. Select the result by TableName and validate its columns, rather than concatenating every Rows array.

2. Radial Search

GET /SearchTools/RadialSearch

Parameter	Type	Description
ra	float	Required. Right ascension (degrees).
dec	float	Required. Declination (degrees).
radius	float	Search radius in arcminutes. Default: 1.
format	string	json, xml, csv.
limit	int	Max results.
whichquery	string	imaging or spectro, as supported by this search.
whichway	string	Coordinate mode, e.g. equatorial.

Example — objects within 2 arcmin of RA=180, Dec=+0.5:

https://skyserver.sdss.org/dr18/SkyServerWS/SearchTools/RadialSearch?ra=180&dec=0.5&radius=2&whichway=equatorial&whichquery=imaging&format=json&limit=10

3. Rectangular Search

GET /SearchTools/RectangularSearch

Parameter	Type	Description
min_ra	float	Minimum RA (degrees).
max_ra	float	Maximum RA (degrees).
min_dec	float	Minimum Dec (degrees).
max_dec	float	Maximum Dec (degrees).
format	string	json, xml, csv.
limit	int	Max results.

4. Object Lookup by ObjID

GET /SearchTools/SqlSearch?cmd=SELECT * FROM PhotoObj WHERE objid={objid}&format=json

5. Spectra Search by Plate-MJD-Fiber

GET /SearchTools/SqlSearch?cmd=SELECT * FROM SpecObj WHERE plate={plate} AND mjd={mjd} AND fiberid={fiberid}&format=json

6. Image Cutout Service

GET /ImgCutout/getjpeg

Parameter	Type	Description
ra	float	Required. RA (degrees).
dec	float	Required. Dec (degrees).
scale	float	Arcsec/pixel. Default: 0.396127.
width	int	Image width in pixels. Default: 512.
height	int	Image height in pixels. Default: 512.

Example:

https://skyserver.sdss.org/dr18/SkyServerWS/ImgCutout/getjpeg?ra=180.0&dec=0.5&scale=0.4&width=256&height=256

Returns JPEG image data.

7. Spectrum Plot/Data

Spectrum FITS files are on the Science Archive Server. Paths depend on instrument, data release, reduction pipeline and plate/fiber formatting. Obtain the actual file URL from the selected release's object page or data model; do not construct one universal spectro/sdss/redux path for every survey.

Important SQL Tables

Table	Description
PhotoObj	Photometric measurements (positions, magnitudes).
SpecObj	Spectroscopic measurements (redshifts, classifications).
Galaxy	View of PhotoObj filtered to galaxies.
Star	View of PhotoObj filtered to stars.

URL-encode cmd (for example curl --get --data-urlencode "cmd=SELECT TOP 10 ..."). Preserve 64-bit object IDs as integers or strings, not floating-point numbers.

Rate Limits

No formal documented rate limits. Queries returning very large result sets may time out. Use TOP N in SQL queries to limit results. For bulk data, use CasJobs (https://skyserver.sdss.org/CasJobs/) with a free account.