Writing queries in ADQL (hints)

• In the select FROM clause the format is always '<table> as t' so 'SELECT * FROM Field f' has to be written as 'SELECT * FROM Field AS f'
• Column names must be preceded by the table name, i.e., 'SELECT u,g,r,z FROM table' does not work. You have to write 'SELECT t.u, t.g, t.r, t.i, t.z FROM table AS t' instead.
• Tables and column names are case sensitive, write 'Field.fieldID' but not 'field.fieldid'.

Low-z QSOs using colors

SDSS: http://cas.sdss.org/dr5/en/help/docs/realquery.asp#lowzqso

AstroGrid: lowzqso.adql

-- Low-z QSO candidates using the color cuts from Gordon Richards.

-- Also a simple query with a long WHERE clause.

SELECT

G.g, G.run, G.rerun, G.camcol, G.field, G.objID

FROM

Galaxy as G

WHERE

( (G.g <= 22) and (G.u - G.g >= -0.27) and (G.u - G.g < 0.71) and (G.g - G.r >= -0.24) and (G.g - G.r < 0.35) and (G.r - G.i >= -0.27) and (G.r - G.i < 0.57) and (G.i - G.z >= -0.35) and (G.i - G.z < 0.70) )

Using three tables

SDSS: http://cas.sdss.org/dr5/en/help/docs/realquery.asp#tables

AstroGrid: threetables.adql

-- Find the parameters for all objects in fields with desired PSF width and range

-- of columns. Now we are using three tables, but it is still a simple query.

SELECT

g.run, g.rerun, g.camCol, f.field, p.objID, p.ra, p.dec, p.Rowc, p.Colc, p.u, p.modelMagErr_u , p.g, p.modelMagErr_g, p.r, p.modelMagErr_r, p.petroMag_r, p.extinction_r, p.petroMagErr_r, p.i, p.modelMagErr_i, p.z, f.psfWidth_r

FROM

PhotoObj as p, Field asf, Segment as g

WHERE

f.fieldID = p.fieldID and f.segmentID = g.segmentID and g.run = 1336 and g.camCol = 1 and f.field between 11 and 13 and f.psfWidth_r > 1.2 and p.colc > 400.0