Automatically generate sequences and triggers for all tables in Oracle - oracle

Question

In my schema, I've migrated about 250 tables from SQL Server to Oracle. The thing is, no sequences or triggers have been created for any of these tables.
Is there an easy way to generate all the table sequences and triggers rather than manually doing this for every table?
An example of a sequence I need would be:
CREATE SEQUENCE "SYSTEM"."SEC_USERS_ID_SEQ"
MINVALUE 0 MAXVALUE 999999999999999999999999
INCREMENT BY 1
START WITH 23
CACHE 20
NOORDER NOCYCLE NOPARTITION;
And the trigger:
create or replace TRIGGER SEC_USERS_TRIG
before INSERT
ON "SYSTEM"."SEC_USERS"
FOR EACH row
BEGIN
IF inserting THEN
IF :NEW."ID" IS NULL THEN
SELECT SEC_USERS_ID_SEQ.nextval INTO :NEW."ID" FROM dual;
END IF;
END IF;
END;

Answer 1

We can generate scripts using the Oracle data dictionary views (the equivalent of MSSQL INFORMATION_SCHEMA). Find out more.
This example generates CREATE SEQUENCE statements. I have followed your example and accepted the default values, which don't need to be coded. The sequence name is derived from table name concatenated with column name and suffixed with "_SEQ". Watch out for Oracle's thirty character limit on object names!
This loop dynamically queries the table to get the current maximum value of the Primary Key column, which is used to derive the STARTS WITH clause.
declare
curr_mx number;
begin
for lrec in ( select ucc.table_name
, ucc.column_name
from user_constraints uc
join user_cons_columns ucc
on ucc.table_name = uc.table_name
and ucc.constraint_name = uc.constraint_name
join user_tab_columns utc
on utc.table_name = ucc.table_name
and utc.column_name = ucc.column_name
where uc.constraint_type = 'P' -- primary key
and utc.data_type = 'NUMBER' -- only numeric columns
)
loop
execute immediate 'select max ('|| lrec.column_name ||') from ' ||lrec.table_name
into curr_mx;
if curr_mx is null then
curr_mx := 0;
end if;
dbms_output.put_line('CREATE SEQUENCE "'|| user || '"."'
|| lrec.table_name ||'_'|| lrec.column_name || '_SEQ" '
||' START WITH ' || to_char( curr_mx + 1 ) ||';'
);
end loop;
end;
/
This code uses DBMS_OUTPUT, so you can spool it to a file for later use. If you're using an IDE like SQL Developer you may need to enable DBMS_OUTPUT. Follow the guidance in this StackOverflow answer.
If you can guarantee that all your tables have a primary key which is a numeric column called ID then you can simplify the select statement. Contrariwise, if some of your primary keys are compound constraints you will need to handle that.
Obviously I plumped for generating sequences because they're simpler. Writing the more complex trigger implementation is left as an exercise for the reader :)

Answer 2

thanks for the script. I altered it a little bit and did the trigger implementation. Feel free to use it.
declare
curr_mx number;
counter number;
seq_name varchar2 (30);
trigger_name varchar2 (30);
begin
for lrec in ( select ucc.table_name
, ucc.column_name
from user_constraints uc
join user_cons_columns ucc
on ucc.table_name = uc.table_name
and ucc.constraint_name = uc.constraint_name
join user_tab_columns utc
on utc.table_name = ucc.table_name
and utc.column_name = ucc.column_name
where uc.constraint_type = 'P' -- primary key
and utc.data_type = 'NUMBER' -- only numeric columns
)
loop
execute immediate 'select (max ('|| lrec.column_name ||')+1) from ' ||lrec.table_name
into curr_mx;
IF curr_mx is null THEN
curr_mx := 0;
END IF;
IF counter is null THEN
counter := 0;
END IF;
/* check length of sequence name, 30 is max */
IF length(lrec.table_name ||'_'|| lrec.column_name || '_SEQ') > 30 THEN
IF length(lrec.column_name || '_SEQ') > 30 THEN
seq_name := counter || '_PKA_SEQ';
ELSE
seq_name := lrec.column_name || '_SEQ';
END IF;
ELSE
seq_name := lrec.table_name ||'_'|| lrec.column_name || '_SEQ';
END IF;
/* check length of trigger name, 30 is max */
IF length(lrec.table_name || '_PKA_T') > 30 THEN
trigger_name := counter || '_PKA_T';
ELSE
trigger_name := lrec.table_name || '_PKA_T';
END IF;
counter := counter +1;
dbms_output.put_line(
'CREATE SEQUENCE "' || seq_name || '"'
||' START WITH ' || to_char( curr_mx + 1 ) ||';'
);
dbms_output.put_line('/');
dbms_output.put_line(
'CREATE OR REPLACE TRIGGER "' || trigger_name || '"'
|| ' BEFORE INSERT ON "' || lrec.table_name || '"'
|| ' FOR EACH ROW '
|| ' BEGIN '
|| ' :new."' || lrec.column_name || '" := "' || seq_name || '".nextval;'
|| ' END;'
);
dbms_output.put_line('/');
end loop;
end;
I also checked if the names of the sequences and triggers are longer than 30 characters because oracle won´t accept these.
EDIT:
Had to put '/' after each line so you can execute all statements at one run.