Oracle merge constants into single table
Question
In Oracle, given a simple data table:
create table data (
id VARCHAR2(255),
key VARCHAR2(255),
value VARCHAR2(511));
suppose I want to "insert or update" a value. I have something like:
merge into data using dual on
(id='someid' and key='testKey')
when matched then
update set value = 'someValue'
when not matched then
insert (id, key, value) values ('someid', 'testKey', 'someValue');
Is there a better way than this? This command seems to have the following drawbacks:
- Every literal needs to be typed twice (or added twice via parameter setting)
- The "using dual" syntax seems hacky
If this is the best way, is there any way around having to set each parameter twice in JDBC?
Solution
I don't consider using dual to be a hack. To get rid of binding/typing twice, I would do something like:
merge into data
using (
select
'someid' id,
'testKey' key,
'someValue' value
from
dual
) val on (
data.id=val.id
and data.key=val.key
)
when matched then
update set data.value = val.value
when not matched then
insert (id, key, value) values (val.id, val.key, val.value);
OTHER TIPS
I would hide the MERGE inside a PL/SQL API and then call that via JDBC:
data_pkg.merge_data ('someid', 'testKey', 'someValue');
As an alternative to MERGE, the API could do:
begin
insert into data (...) values (...);
exception
when dup_val_on_index then
update data
set ...
where ...;
end;
I prefer to try the update before the insert to save having to check for an exception.
update data set ...=... where ...=...;
if sql%notfound then
insert into data (...) values (...);
end if;
Even now we have the merge statement, I still tend to do single-row updates this way - just seems more a more natural syntax. Of course, merge really comes into its own when dealing with larger data sets.
Use a stored procedure