Ontology asks, What exists?,
to which the answer is Everything.
— W.V.O. Quine, Word and Object


Line comment

q)/Oh what a lovely day
Trailing comment
q)2+2  /I know this one
Multiline comment
    Oh what a beautiful morning
    Oh what a wonderful day
ignore this and what follows
the restroom at the end of the universe


noun examples
atom 42; "a"; 1b; 2012.08.04; `ibm
vector (43;44;45); "abc"; 0101b; `ibm`goo; 2012.09.15 2012.07.05
list (43;"44";45); ("abc";0101b;);(("abc";1 2 3); `ibm`abc)
dictionary `a`b`c!42 43 44; `name`age!(`john`carol`ted;42 43)
table ([]name:`john`carol`ted; age:42 43 44)
keyed table ([name:`john`carol`ted] age:42 43 44)

Lists are zero or more items, separated by semicolons, and enclosed in parentheses. An item can be any noun.

A vector is a list in which all items are of the same datatype. It can be represented without parentheses. Numeric, boolean, char and symbol vectors have their own forms.

type example
numeric 42 43 44
date 2012.09.15 2012.07.05
char "abc"
boolean 0101b
symbol `ibm`att`ora

The syntactic class of nouns includes all data structures. Operators, functions and adverbs can be given noun syntax by listing or parenthesising them.



Attributes are metadata that apply to lists of special form. They are often used on a dictionary domain or a table column to reduce storage requirements or speed retrieval.

example overhead
`s#2 2 3 sorted 0
`u#2 4 5 unique 16*u
`p#2 2 1 parted (4*u;16*u;4*u+1)
`g#2 1 2 grouped (4*u;16*u;4*u+1;4*n)

The byte overheads use n (number of elements) and u (number of uniques).

  • `u is for unique lists.
  • `p and `g are for lists with a lot of repetition.

`s#, `u# and `g# are preserved on append in memory, if possible. Only `s# is preserved on append to disk.

To set or unset an attribute:

q)`s#1 2 3
`s#1 2 3
q)`#`s#1 2 3
1 2 3
Setting or unsetting an attribute other than s, i.e. upg, causes a copy of the object to be made. Setting/unsetting the s attribute on a list which is already sorted will not cause a copy to be made, and hence will affect the original list in-place. Setting the s attr on a dictionary or table, where the key is already in sorted order, in order to obtain a step-function, causes the s attribute to be set in place for the key but copies the outer object.
q)t:([1 2 4]y:7 8 9);`s#t;attr each (t;key t)

Names and namespaces

Names consist of upper- and lower-case alphabetics. They may contain, but not begin with, underscores and numbers. For example: a, foo, foo2_bar.

A namespace is a container or context within which a name resolves to a unique value. Namespaces are children of the root namespace (usually just root) and are designated by a dot prefix. Names in the root have no prefix. The root namespace of a q session is parent to multiple namespaces, e.g. h, Q and z. (Namespaces with 1-character names – of either case – are reserved for use by Kx.)

q).z.p                         / UTC timestamp

Names in context


Functions are:

  1. operators and primitive functions, eg +, count
  2. as defined in the lambda notation, eg {x+2*y}
  3. as derived from (1) and (2) by adverbs, eg +/, count'
  4. q-SQL functions, e.g. select

Functions are first-class objects and can be passed as arguments to other functions. Functions that take other functions as arguments are known as higher-order functions.

Reserved words

The following reserved words denote functions that are not also operators.

Aabs, acos, aj, aj0, all, any, asc, asin, atan, attr, avg, avgs
Cceiling, cols, cos, count
Ddelete, deltas, desc, dev, differ, distinct
Eej, enlist, eval, exec, exit, exp
Ffills, first, fkeys, flip, floor
Gget, getenv, group, gtime
Hhclose, hcount, hdel, hopen, hsym
Iiasc, idesc, inv
Kkey, keys
Llast, load, log, lower, ltime, ltrim
Mmax, maxs, md5, med, meta, min, mins
Nneg, next, not, null
Pparse, prd, prds, prev
Rrand, rank, ratios, raze, read0, read1, reciprocal, reval, reverse, rload, rotate, rsave, rtrim
Ssave, sdev, select, show, signum, sin, sqrt, ssr, string, sublist, sum, sums, sv decode, svar, system
Ttables, tan, til, trim, type
Uungroup, update, upper
Vvalue, var, view, views
Wwhere, wj, wj1

.Q.res (reserved words)


Operators are primitive binary functions that may be applied infix.

q)|[2;3]                 / maximum, prefix form
q)2|3                    / maximum, infix form
q)rotate[2;0 1 2 3 4 5]  / prefix form
2 3 4 5 0 1
q)2 rotate 0 1 2 3 4 5   / infix form
2 3 4 5 0 1
Operators are denoted by glyphs or reserved words or both – see note below on minimum and maximum. (They cannot be defined using the lambda notation.)


=equal<>not equal~match
<less than<=less than or equal>greater than>=greater than or equal
+plus-minus*times%divided by
#take,join^fill; coalesce_drop; cut
!dict; key; enumerate; ints to enum; update; delete

Minimum and maximum

The minimum operator is denoted by both the & glyph and the reserved word and. The maximum operator is denoted by both the | glyph and the reserved word or.

Reserved words

The following reserved words denote operators.

Aand, asof
Bbin, binr
Ccor, cov, cross, cut
Ddiv, dsave
Eeach, ema, except
Iij, in, insert, inter
Llike, lj, ljf, lsq
Mmavg, mcount, mdev, mmax, mmin, mmu, mod, msum
Oor, over
Ppeach, pj, prior
Sscan, scov, set, setenv, ss, sublist, sv consolidate
Uuj, union, upsert
Vvs encode, vs split
Wwavg, within, wsum
Xxasc, xbar, xcol, xcols, xdesc, xexp, xgroup, xkey, xlog, xprev, xrank

.Q.res (reserved words)


Adverbs are primitive higher-order functions: they return derivatives (derived functions). They are denoted by six overloaded glyphs: ', /, \, ':, /: and \:.

q)+/[2 3 4]  / reduce 2 3 4 with +
q)*/[2 3 4]  / reduce 2 3 4 with *
Adverbs, Adverb syntax

Control words

The control words do, if and while govern evaluation.


A view is a calculation that is re-evaluated only if the values of the underlying dependencies have changed since its last evaluation. Views can help avoid expensive calculations by delaying propagation of change until a result is demanded.

The syntax for the definition is

The act of defining a view does not trigger its evaluation.

A view should not have side-effects, i.e. should not update global variables.

Views tutorial, view, views, .Q.view (subview)

System commands

Expressions beginning with \ are system commands or multiline comments (see above).

q)/ load the script in file my_app.q
q)\l my_app.q


A script is a text file; its lines a list of expressions and/or system commands, to be executed in sequence. By convention, script files have the extension q.

Within a script

  • function definitions may extend over multiple lines
  • an empty comment begins a multiline comment.