Org has three predefined Emacs Lisp functions for lookups in tables.
Searches for the first element S in list S-LIST for which
(PREDICATE VAL S)
is non-nil; returns the value from the corresponding position in
list R-LIST. The default PREDICATE is
equal. Note that the parameters VAL and S
are passed to PREDICATE in the same order as the
corresponding parameters are in the call to org-lookup-first,
where VAL precedes S-LIST. If
R-LIST is nil, the matching element S of
S-LIST is returned.
Similar to org-lookup-first above, but searches for the last
element for which PREDICATE is non-nil.
Similar to org-lookup-first, but searches for all elements for
which PREDICATE is non-nil, and returns all
corresponding values. This function can not be used by itself in
a formula, because it returns a list of values. However, powerful
lookups can be built when this function is combined with other Emacs
Lisp functions.
If the ranges used in these functions contain empty fields, the ‘E’ mode for the formula should usually be specified: otherwise empty fields are not included in S-LIST and/or R-LIST which can, for example, result in an incorrect mapping from an element of S-LIST to the corresponding element of R-LIST.
These three functions can be used to implement associative arrays, count matching cells, rank results, group data, etc. For practical examples see this tutorial on Worg.