When you execute immediate
, the command you run should not have a semi-colon on the end; that is a command separator in SQL Developer (and SQL*Plus, and other clients), not part of the SQL statement itself.
SELECT 'CREATE SEQUENCE ID_SEQ MINVALUE 1 MAXVALUE 9999999999 START WITH '
|| (max(ID)+1) || ' INCREMENT BY 1 CACHE 20' INTO y FROM TEST_TABLE;
This is shown in the examples for plain SQL. Just to help confuse you though, if you are using PL/SQL within the dynamic SQL, you do still need semi-colons appropriate to PL/SQL itself - though not the executing /
you'd use to run it directly from a client. This is shown in other examples.