VizieR help - FAQ - Tutorial

Qualifying fields is adding one ore more constraints on some of the columns. The qualification syntax follows the ASU protocol:

Some typical examples:

||keep only non-blank (i.e. specified, or not-null) values:  ||  
	!= ||
||restrict a number to the range 12.0 to 12.5:   ||  
	12.0 .. 12.5 ||
||restrict a date to before June 1, 2000:   ||  
	< 2000.06.01 ||
||restrict a stellar spectral type ((char) column) to early types:  ||  
	=*[OBA]* ||

Numeric fields
The following table describes all operators available on numeric fields (i.e. not flagged by (char)):

=Strict equality (default)=10
>=Greater or equal>=10
>Strictly greater>10
<=Smaller or equal<=10
<Strictly smaller<10
..Range of numbers5..10
+/- Range defined by its mean and semi-amplitude (*) 8+/-2
&AND (logical operator)1..5 & 7..9
|OR (logical operator)1..5 | 7..9
,List of values0,1,2
<<; List of values.
Each value results in a separated table, in a way similar to the output from a list of targets.
!NOT (logical operator)! 1..5
(*) The +/- operator may alternatively be written ± if your keyboard allows this symbol. Note also that for DATE/TIME values, the semi-amplitude can only be given as a number representing decimal days, as e.g.   07-Apr-2001 12:00 ± 3.5    for the days 4 to 10 April 2001 (facility added in April 2001)
(**) since 23/06/2009

Values in Numeric fields
What follows the comparison operators are generally numbers; in a few cases, several ways of writing values are possible:

nullUnspecified (blank)value (<0)|null
now Current date and time (DATE only) < now
RA Sexagesimal hours, minutes, seconds of time 23 56 .. 00 04
Right ascension in decimal degrees 359 .. 001
DE Sexagesimal degrees, minutes, seconds of arc +41 45 .. +42 30
Declination in decimal degrees +41.75 .. +42.50
DATE/TIME UT Date and time, alphabetic month >= 1-Jan-1996
UT Date and Time, numeric month >= 1996.01.01 00:00:00
Julian Date >=JD2450083.5

Character fields
The following table describes all operators available on character fields (i.e. flagged by (char)):
~Caseless pattern matching (default) ~ngc*3532*
=Pattern matching=NGC*3532*
=~Caseless equality=~ngc
==Strict equality==NGC
~||-separated list of caseless pattern matchings ~|O*pec|WR*
=, comma-separated list of alternatives =,HST,IRAS
=| |-separated list of alternatives =|HST|IRAS
!=, exclusion of a comma-separated list of alternatives !=,HST,IRAS
!~NOT caseless pattern matching !~[obafgkm]*
!NOT pattern matching ![OBAFGKM]*
!=Strict inequality!=NGC
>=Alphabetically greater or equal >=A
>Alphabetically strictly greater >M 51
<=Alphabetically smaller or equal <=B*
<Alphabetically strictly smaller < NGC
<<; List of values separated by ;(*) <<;val1;val2;val3
(*) (facilities added in June 2009)

Pattern matching symbols
What follows the pattern matching operators (~ = !~ !) is a pattern string which contains the following symbols:

[...] One of the characters defined within the brackets =[OBA]*
The - (dash or minus) indicates a range of characters =[A-Za-z]*
[^...] Any single character NOT contained within the brackets =[^OBAFGMN]*
*Replaces 0 to n characters[OB]*
?Replaces 1 characterA?C*

Note about Heading Blanks: when no operator is listed, the leading blanks (blanks at the left of a character column) are ignored.

last update: 18 Jan 2013