I have table TEST_TABLE having 3 columns COL1(Number), COL2(Varchar), COL3(Date).
I want to find the result of the below query in an anonymous block for two different transactions. One for the current transaction and the other for the immediately previous transaction. How to do it using SCN?
BEGIN
Select col3 into v_curr_date from test_table where col1=123; --Current
uncommitted Transaction
Select col3 into v_prev_date from test_table where col1=123; --How to
modify this query to find for immediately Previous committed Transaction.
END ;
Below one will gives you the latest committed date happened on a table. SCN_TO_TIMESTAMP takes as an argument a number that evaluates to a system change number (SCN), and returns the approximate timestamp associated with that SCN. So modify your query accordingly.
DECLARE
v_prev_date date;
BEGIN
Select SCN_TO_TIMESTAMP(ORA_ROWSCN) into v_prev_date
from test_table where col1=123;
dbms_output.put_line(v_prev_date );
end;
Related
I want to write a trigger so that when decom_date is inserted or updated the week of the year is updated to the corresponding value.
This is what I have so far, but after inserting a date the week is still null.
create or replace trigger test_trigger
before insert on check_decom
for each row
begin
if inserting then
update check_decom set decom_week= (select to_char(to_date(decom_date,'DD-
MON-YY'),'WW') as week from check_decom) ;
end if;
end;
/
SQL> select * from check_decom;
DECOM_DATE DECOM_WEEK
------------------------------ ----------
23-JUN-17
What am I doing wrong?
Example for Week of a year
SQL> select to_char(to_date(sysdate,'DD-MON-YY'),'WW') as week from dual;
WE
--
28
You're doing a couple of things wrong, starting with date handling. Your decom_date column should be defined as a DATE column - it looks like it might be a string in your sample output. But your handling with sysdate is also wrong, as you're implicitly converting to a string in order to convert it back to a date, which is both pointless and prone to error as this might happen in a session which has different NLS settings. If your column is actually a DATE then you should not be calling to_date() against that either; and if it is a string then that conversion is valid but it should be a DATE.
Then your trigger is querying and trying to update the table that the trigger is against. With no data that doesn't error but doesn't do anything as there is no existing row to update - the one you are inserting doesn't exist yet. If there was data you would get a mutating table error, if you didn't get a too-many-rows exception from the select part.
Row-level triggers can access NEW and OLD pseudorecords to see and manipulate the affected row; you don't need to (and generally can't) use DML queries to access the data in the row you're manipulating.
If your table was defined with a date column and a number column:
create table check_decom(decom_date date, decom_week number);
then your trigger might look something like:
create or replace trigger test_trigger
before insert on check_decom
for each row
begin
if inserting then
:new.decom_week := to_number(to_char(:new.decom_date, 'WW'));
end if;
end;
/
although the if inserting check is a bit pointless as the trigger will only fire on insert anyway. Which in itself might be an issue; you perhaps want it to be set on update as well, but the logic the same, so would be:
create or replace trigger test_trigger
before insert or update on check_decom
for each row
begin
:new.decom_week := to_number(to_char(:new.decom_date, 'WW'));
end;
/
which does what you want:
insert into check_decom (decom_date) values (date '2017-06-23');
1 row inserted.
select * from check_decom;
DECOM_DAT DECOM_WEEK
--------- ----------
23-JUN-17 25
But I wouldn't do this with a trigger at all. From Oracle 11g you can use a virtual column instead:
create table check_decom (
decom_date date,
decom_week generated always as (to_number(to_char(decom_date, 'WW')))
);
Table CHECK_DECOM created.
insert into check_decom (decom_date) values (date '2017-06-23');
1 row inserted.
select * from check_decom;
DECOM_DAT DECOM_WEEK
--------- ----------
23-JUN-17 25
I am using ORACLE 12c.
On a table I have 2 triggers, both "before update".
One of the triggers fires while updating a column and within this trigger another column gets a new value. The second trigger should fire while updating this second column. But he did not.
create table TRIGGER_TEST
(
col1 varchar2(64),
col2 varchar2(64),
col3 varchar2(64)
);
create or replace trigger TR_TRIGGER_TEST_1
before update of COL1 on TRIGGER_TEST
for each row
begin
dbms_output.put_line('here we are in TR_TRIGGER_TEST_1');
:new.col2 := 'only testing';
end;
/
create or replace trigger TR_TRIGGER_TEST_2
before update of COL2 on TRIGGER_TEST
for each row
begin
dbms_output.put_line('here we are in TR_TRIGGER_TEST_2');
:new.col3 := 'trigger_test_2 has fired';
end;
/
insert into TRIGGER_TEST values ('1_col1','1_col2','1_col3');
select * from TRIGGER_TEST;
COL1 COL2 COL3
----------------------------------------------------------------
1_col1 1_col2 1_col3
After I have inserted the row I perform an UPDATE. And I expect COL1=
"now we will see", COL2="only testing" and COL3 = "trigger_test_2 has fired".
update TRIGGER_TEST set COL1 = 'now we will see';
But what I get is this:
select * from TRIGGER_TEST;
COL1 COL2 COL3
----------------------------------------------------------------
now we will see only testing 1_col3
Can anybody explain this to me? I am really sure, that with former ORACLE versions this szenario has worked. But now it does not.
I am really sure, that with former ORACLE versions this szenario has worked.
It has not. I ran your code in 11gR2 and got the same result:
set serveroutput on
update TRIGGER_TEST set COL1 = 'now we will see';
here we are in TR_TRIGGER_TEST_1
1 row updated.
select * from TRIGGER_TEST;
COL1 COL2 COL3
------------------------------ ------------------------------ ------------------------------
now we will see only testing 1_col3
The before update of COL2 on TRIGGER_TEST is a DML event clause. You are creating simple DML triggers:
A DML trigger is created on either a table or view, and its triggering event is composed of the DML statements DELETE, INSERT, and UPDATE. ...
When you issue your update that DML causes the first trigger to fire. But when you assign a new value inside that trigger:
:new.col2 := 'only testing';
.. that is not a DML statement - it is not a separate update.
If assigning a value in that way did cause a trigger to fire, then if you instead did:
:new.col1 := 'something';
... then that first trigger would fire again, recursively, until you hit the error ORA-00036: maximum number of recursive SQL levels (50) exceeded. That would obviously be bad.
You will have to repeat the assignment of col3 in the first trigger if that is what you need to happen. For more complicated side-effects that you want to happen whether you hit either trigger, you could have a procedure that does any necessary actions (that don't affect this table), and then call that from both triggers. Although then you'd need a mechanism to make sure the procedure isn't called twice if a DML update touches both columns - which would cause both triggers to fire.
"update of COL2" in a trigger would mean update using a SQL statement such as UPDATE or MERGE, and not otherwise. Why dont you code the second trigger in the first ?
I am new to Oracle. I have a table in Oracle which has 4 columns Period, Open_Flag,Creation_Dt,Updated_By.
The Period column is the Primary key of the table. I have created a proc which will check the value of period from input parameter in the table, if its existing, the value of Open_flag has to be updated else a new record shall be inserted.
create or replace
PROCEDURE PROC_REF_SAP_PERIOD(
V_PERIOD IN NUMBER,V_OPEN_FLAG IN VARCHAR2,V_CREATION_DT IN DATE,V_UPDATED_BY IN VARCHAR2)
AS
BEGIN
MERGE INTO REF_SAP_PERIOD T
USING (SELECT * FROM REF_SAP_PERIOD WHERE PERIOD=V_PERIOD )S
ON (T.PERIOD=S.PERIOD )
WHEN MATCHED THEN UPDATE SET OPEN_FLAG = V_OPEN_FLAG --WHERE PERIOD=V_PERIOD AND CREATION_DT=V_CREATION_DT AND UPDATED_BY=V_UPDATED_BY
WHEN NOT MATCHED THEN INSERT (PERIOD,OPEN_FLAG,CREATION_DT,UPDATED_BY) VALUES (V_PERIOD,V_OPEN_FLAG,V_CREATION_DT,V_UPDATED_BY);
END;
The issue is that the Update is working well in this case, however, the insert is not working. Please help.
You are merging table with itself, filtered by period. Obviously, it will never see your non-existent values in itself.
Try this line instead of your USING line:
using (select V_PERIOD "period" from dual)S
In Oracle, I have a requirement where in I need to insert records from Source to Target and then update the PROCESSED_DATE field of source once the target has been updated.
1 way is to use cursors and loop row by row to achieve the same.
Is there any other way to do the same in an efficient way?
No need for a cursor. Assuming you want to transfer those rows that have not yet been transfered (identified by a NULL value in processed_date).
insert into target_table (col1, col2, col3)
select col1, col2, col3
from source_table
where processed_date is null;
update source_table
set processed_date = current_timestamp
where processed_date is null;
commit;
To avoid updating rows that were inserted during the runtime of the INSERT or between the INSERT and the update, start the transaction in serializable mode.
Before you run the INSERT, start the transaction using the following statement:
set transaction isolation level SERIALIZABLE;
For more details see the manual:
http://docs.oracle.com/cd/E11882_01/server.112/e26088/statements_10005.htm#i2067247
http://docs.oracle.com/cd/E11882_01/server.112/e25789/consist.htm#BABCJIDI
A trigger should work. The target table can have a trigger that on update, updates the source table's column with the processed date.
My preferred solution in this sort of instance is to use a PL/SQL array along with batch DML, e.g.:
DECLARE
CURSOR c IS SELECT * FROM tSource;
TYPE tarrt IS TABLE OF c%ROWTYPE INDEX BY BINARY_INTEGER;
tarr tarrt;
BEGIN
OPEN c;
FETCH c BULK COLLECT INTO tarr;
CLOSE c;
FORALL i IN 1..tarr.COUNT
INSERT INTO tTarget VALUES tarr(i);
FORALL i IN 1..tarr.COUNT
UPDATE tSource SET processed_date = SYSDATE
WHERE tSource.id = tarr(i).id;
END;
The above code is an example only and makes some assumptions about the structure of your tables.
It first queries the source table, and will only insert and update those records - which means you don't need to worry about other sessions concurrently inserting more records into the source table while this is running.
It can also be easily changed to process the rows in batches (using the fetch LIMIT clause and a loop) rather than all-at-once like I have here.
Got another answer from some one else. Thought that solution seems much more reasonable than enabling isolation level as all my new records will have the PROCESSED_DATE as null (30 rows which inserted with in the time the records got inserted in Target table)
Also the PROCESSED_DATE = NULL rows can be updated only by using my job. No other user can update these records at any point of time.
declare
date_stamp date;
begin
select sysdate
into date_stamp
from dual;
update source set processed_date = date_stamp
where procedded_date is null;
Insert into target
select * from source
where processed_date = date_stamp;
commit;
end;
/
Let me know any further thoughts on this. Thanks a lot for all your help on this.
I have an application that uses the Oracle MERGE INTO... DML statement to update table A to correspond with some of the changes in another table B (table A is a summary of selected parts of table B along with some other info). In a typical merge operation, 5-6 rows (out of 10's of thousands) might be inserted in table B and 2-3 rows updated.
It turns out that the application is to be deployed in an environment that has a security policy on the target tables. The MERGE INTO... statement can't be used with these tables (ORA-28132: Merge into syntax does not support security policies)
So we have to change the MERGE INTO... logic to use regular inserts and updates instead. Is this a problem anyone else has run into? Is there a best-practice pattern for converting the WHEN MATCHED/WHEN NOT MATCHED logic in the merge statement into INSERT and UPDATE statements? The merge is within a stored procedure, so it's fine for the solution to use PL/SQL in addition to the DML if that is required.
Another way to do this (other than Merge) would be using two sql statements one for insert and one for update. The "WHEN MATCHED" and "WHEN NOT MATCHED" can be handled using joins or "in" Clause.
If you decide to take the below approach, it is better to run the update first (sine it only runs for the matching records) and then insert the non-Matching records. The Data sets would be the same either way, it just updates less number of records with the order below.
Also, Similar to the Merge, this update statement updates the Name Column even if the names in Source and Target match. If you dont want that, add that condition to the where as well.
create table src_table(
id number primary key,
name varchar2(20) not null
);
create table tgt_table(
id number primary key,
name varchar2(20) not null
);
insert into src_table values (1, 'abc');
insert into src_table values (2, 'def');
insert into src_table values (3, 'ghi');
insert into tgt_table values (1, 'abc');
insert into tgt_table values (2,'xyz');
SQL> select * from Src_Table;
ID NAME
---------- --------------------
1 abc
2 def
3 ghi
SQL> select * from Tgt_Table;
ID NAME
---------- --------------------
2 xyz
1 abc
Update tgt_Table tgt
set Tgt.Name =
(select Src.Name
from Src_Table Src
where Src.id = Tgt.id
);
2 rows updated. --Notice that ID 1 is updated even though value did not change
select * from Tgt_Table;
ID NAME
----- --------------------
2 def
1 abc
insert into tgt_Table
select src.*
from Src_Table src,
tgt_Table tgt
where src.id = tgt.id(+)
and tgt.id is null;
1 row created.
SQL> select * from tgt_Table;
ID NAME
---------- --------------------
2 def
1 abc
3 ghi
commit;
There could be better ways to do this, but this seems simple and SQL-oriented. If the Data set is Large, then a PL/SQL solution won't be as performant.
There are at least two options I can think of aside from digging into the security policy, which I don't know much about.
Process the records to merge row by row. Attempt to do the update, if it fails to update then insert, or vise versa, depending on whether you expect most records to need updating or inserting (ie optimize for the most common case that will reduce the number of SQL statements fired), eg:
begin
for row in (select ... from source_table) loop
update table_to_be_merged
if sql%rowcount = 0 then -- no row matched, so need to insert
insert ...
end if;
end loop;
end;
Another option may be to bulk collect the records you want to merge into an array, and then attempted to bulk insert them, catching all the primary key exceptions (I cannot recall the syntax for this right now, but you can get a bulk insert to place all the rows that fail to insert into another array and then process them).
Logically a merge statement has to check for the presence of each records behind the scenes anyway, and I think it is processed quite similarly to the code I posted above. However, merge will always be more efficient than coding it in PLSQL as it will be only 1 SQL call instead of many.