OrientDB - Update with SUBSELECT - orientdb

Question

I want to update some rows of my table basing on other rows of the same table:
I try this:
UPDATE MyTable set myField =
(SELECT T1.myField
FROM MyTable T1
WHERE T1.id.substring(start,stop) = MyTable.id.substring(start,stop))
But OrientDB throws an error like this:
com.orientechnologies.orient.core.sql.OCommandSQLParsingException: Error on parsing command at position #XXX: Invalid keyword 'T1' Command:

Answer 1

first of all you in OrientDB you can't use Alias on Classes.
In this case you could use $parent.$current in a subquery, something like:
> update MyTable set myField = (
> select myField
> from MyTable
> where myField is null
> and id.substring(8,13) = $parent.$current.id.substring(8,13) and something else...
> ) where myField is null and something else...
Be careful to the length of the id...
Best Regards
M.

Answer 2

This is not a string update, but an integer update in place. Using the provided GratefulDeadDatabase, you can do:
CONNECT remote:localhost/GratefulDeadConcerts;
SELECT performances FROM v;
----+------+------------
# |#CLASS|performances
----+------+------------
0 |null |null
1 |null |5
2 |null |1
3 |null |531
4 |null |394
----+------+------------
UPDATE v SET performances = eval('performances + 2') WHERE performances IS NOT NULL;
SELECT performances FROM v;
----+------+------------
# |#CLASS|performances
----+------+------------
0 |null |null
1 |null |7
2 |null |3
3 |null |533
4 |null |396
----+------+------------
So the update works on the data in place. I'm fairly new to OrientDB so maybe an expert can tell me if I just did something horribly horribly wrong.
UPDATE
Notice that in your example you are updating the table with values from the same table. That is, from MyTable into MyTable (unless I misunderstood your query) and even within the same row. You can use criteria on the WHERE clause to only update rows of interest. In my example, that was
WHERE performances IS NOT NULL