oracle decode
from: http://www.adp-gmbh.ch/ora/sql/decode.html
decode (expression, search_1, result_1)
decode (expression, search_1, result_1, search_2, result_2)
decode (expression, search_1, result_1, search_2, result_2, ...., search_n, result_n)
decode (expression, search_1, result_1, default)
decode (expression, search_1, result_1, search_2, result_2, default)
decode (expression, search_1, result_1, search_2, result_2, ...., search_n, result_n, default)
decode compares expression to the search_x expressions and, if matches, returns result_x. If not, returns default, or, if default is left out, null.
a sample:
create table a (x int, b int);
insert into a values (1,2);
insert into a values (1,3);
insert into a values (2,4);
insert into a values (2,5);
insert into a values (3,6);
select * from a where b = decode (x,1,2,2,4);
X B
---------- ----------
1 2
2 4