query: if exists UPDATE else INSERT?

[Alexander Newald]

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Hello,

I'm looking for a solution to write a sql query that inserts a set of =
data if the data id is not present and otherwise update the set.

I have a table with id (char(8)) and value (int(8))

To make my problem clear:

There is no set with id =3D "20030713"
insert into table values ("20030713","10");

The next set is ("20030713","20") but as a set with 20030713 is already =
available I like to have
update table set value =3D value + 20 where id =3D "20030713"

I tried the "replace" command but I fail to get the "value =3D value + =
20" working.

The problem is that the query is called from within a programm that only =
can call a query but not get some data back.

Also a solution in form of

mysql>
$w =3D select value from table where id =3D "20030713";
delete from table where id =3D "20030713";
insert into table values ("20030713",$w + 20);
<mysql

would be fine but I think that $w =3D part isn't working with mysql ;-)

Its no solution to simply make the table accept duplicate entries for id =
and make a "sum(value) group by id" because I think it will be a =
performace problem if I have thousends of datasets a day - If I'm wrong =
let me know.

Any hints how to manage this??

Alexander Newald
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