I've come up with the following trigger to extract all the column names which are updated when a table row update statement is executed...
but the problem is if there are more columns(atleast 100 cols), the performance/efficiency comes into concern
sample trigger code:
set define off;
create or replace TRIGGER TEST_TRIGG
AFTER UPDATE ON A_AAA
FOR EACH ROW
DECLARE
mytable varchar2(32) := 'A_AAA';
mycolumn varchar2(32);
updatedcols varchar2(3000);
cursor s1 (mytable varchar2) is
select column_name from user_tab_columns where table_name = mytable;
begin
open s1 (mytable);
loop
fetch s1 into mycolumn;
exit when s1%NOTFOUND;
IF UPDATING( mycolumn ) THEN
updatedcols := updatedcols || ',' || mycolumn;
END IF;
end loop;
close s1;
--do a few things with the list of updated columns
dbms_output.put_line('updated cols ' || updatedcols);
end;
/
Is there any alternative way to get the list?
Maybe with v$ tables (v$transaction or anything similar)?
No its the best way to get UPDATED column by UPDATING()
and you can change your code using implicit cursor like this, it will be a little bit faster
set define off;
create or replace TRIGGER TEST_TRIGG
AFTER UPDATE ON A_AAA
FOR EACH ROW
DECLARE
updatedcols varchar2(3000);
begin
for r in (select column_name from user_tab_columns where table_name ='A_AAA')
loop
IF UPDATING(r.column_name) THEN
updatedcols := updatedcols || ',' || r.column_name;
END IF;
end loop;
dbms_output.put_line('updated cols ' || updatedcols);
end;
/
Faced with a similar task, we ended up writing a pl/sql procedure which lists the columns of the table and generates the full trigger body for us, with static code referencing :new.col and :old.col. The execution of such trigger should probably be faster (though we didn't compare).
However, the downside is that when you later add a new column to the table, it's easy to forget to update the trigger body. It probably can be managed somehow with a monitoring job or elsehow, but for now it works for us.
P.S. I became curious what that updating('COL') feature does, and checked it now. I found out that it returns true if the column is present in the update statement, even if the value of the column actually didn't change (:old.col is equal to :new:col). This might generate unneeded history records, if the table is being updated by something like Java Hibernate library, which (by default) always specifies all columns in the update statements it generates. In such a case you might want to actually compare the values from inside the trigger body and insert the history record only in case the new value differs from the old value.
Related
I want to pass a table name and schema into a procedure, and have it generate insert, update and delete statements for the particular table. This is part of an automated testing solution (in a development environment) in which I need to test some change data capture. I want to make this dynamic as it is going to be need to be done for lots of different tables over a long period of time, and I need to call it via a REST request through ORDS, so don't want to have to make an endpoint for every table.
Update and delete are fairly easy, however I am struggling with the insert statement. Some of the tables being passed in have hundreds of columns with various constraints, fks etc. so I think it makes sense to just manipulate an existing record by changing only the primary key. I need to be able to modify the primary key to a new value known to me beforehand (e.g. '-1').
Ideally I would create a dynamic rowtype, and select into where rownum = 1, then loop round the primary keys found from all_constraints, and update the rowtype.pk with my new value, before inserting this into the table. Essentially the same as this but without knowing the table in advance.
e.g. rough idea
PROCEDURE manipulate_records(p_owner in varchar2, p_table in varchar2)
IS
cursor c_pk is
select column_name
from all_cons_columns
where owner = p_owner
and constraint_name in (select constraint_name
from all_constraints
where table_name = p_table
and constraint_type = 'P');
l_row tbl_passed_in%ROWTYPE --(I know this isn't possible but ideally)
BEGIN
-- dynamic sql or refcursor to collect a record
select * into tbl_passed_in from tablename where rownum = 1;
-- now loop through pks and reassign their values to my known value
for i in c_pk loop
...if matches then reassign;
...
end loop;
-- now insert the record into the table passed in
END manipulate_records;
I have searched around but haven't found any examples which fit this exact use case, where an unknown column needs to be modified and insert into a table.
Depending on how complex your procedure is, you might be able to store it as a template in a CLOB. Then pull it in, replace table and owner, then compile it.
DECLARE
prc_Template VARCHAR2(4000);
vc_Owner VARCHAR2(0008);
vc_Table VARCHAR2(0008);
BEGIN
vc_Table := 'DUAL';
vc_Owner := 'SYS';
-- Pull code into prc_Template from CLOB, but this demonstrates the concept
prc_Template := 'CREATE OR REPLACE PROCEDURE xyz AS r_Dual <Owner>.<Table>%ROWTYPE; BEGIN NULL; END;';
prc_Template := REPLACE(prc_Template,'<Owner>',vc_Owner);
prc_Template := REPLACE(prc_Template,'<Table>',vc_Table);
-- Create the procedure
EXECUTE IMMEDIATE prc_Template;
END;
Then you have the appropriate ROWTYPE available:
CREATE OR REPLACE PROCEDURE xyz AS r_Dual SYS.DUAL%ROWTYPE; BEGIN NULL; END;
But you can't create the procedure and run it in the same code block.
I have a procedure in which I want to fetch all records from cte into Names variable. But this code is not writing into names from CTE. How can I fetch records into names so that I can later loop through names and get content of field_name?
CREATE OR REPLACE PROCEDURE sp_market
IS
Names VARCHAR2(32767);
BEGIN
WITH CTE(sqql) As
(
SELECT field_name sqql FROM pld_medicare_config
)
SELECT sqql into Names from CTE;
END sp_market;
SELECT sqql into Names from CTE;
You are assigning multiple rows returned from table to a variable, which will fail.
You could simply use a CURSOR FOR LOOP which will create an implicit cursor and you can loop through the names:
CREATE OR REPLACE PROCEDURE sp_market IS
BEGIN
FOR i IN (
SELECT field_name
FROM pld_medicare_config
)
LOOP
-- Your logic goes here
dbms_output.put_line(i.field_name);
END LOOP;
END;
/
I think your best bet is to create a associative array and use BULK COLLECT to populate the table. In its simplest form, the code would look like this:
CREATE OR REPLACE PROCEDURE sp_market IS
TYPE lt_names IS TABLE OF VARCHAR2(32767) INDEX BY PLS_INTEGER;
l_tNames lt_names;
BEGIN
SELECT field_name
BULK COLLECT INTO l_tNames
FROM pld_medicare_config
IF l_tNames.COUNT() > 0 THEN
FOR i IN l_tNames.FIRST..l_tNames.LAST LOOP
NULL; --REPLACE WITH YOUR LOGIC
END LOOP;
END IF;
END;
/
A few notes:
I'm assuming that you've set MAX_STRING_SIZE to EXTENDED. Otherwise, you'll have an issue with VARCHAR2 that big.
As I said, that is the simplest way to do this. If you're expecting a huge result set, you'll want to look into chunking it up. This Oracle blog post is very helpful in giving you multiple options for how to perform bulk processing. (Blog Post)
declare
vquery long;
cursor c1 is
select * from temp_name;
begin
for i in c1
loop
vquery :='INSERT INTO ot.temp_new(id)
select '''||i.id||''' from ot.customers';
dbms_output.put_line(i.id);
end loop;
end;
/
Output of select * from temp_name is :
ID
--------------------------------------------------------------------------------
customer_id
1 row selected.
I have customers table which has customer_id column.I want to insert all the customer_id into temp_new table but it is not being inserted. The PLSQL block executes successfully but the temp_new table is empty.
The output of dbms_output.put_line(i.id); is
customer_id
What is wrong there?
The main problem is that you generate a dynamic statement that you never execute; at some point you need to do:
execute immediate vquery;
But there are other problems. If you output the generated vquery string you'll see it contains:
INSERT INTO ot.temp_new(id)
select 'customer_id' from ot.customers
which means that for every row in customers you'll get one row in temp_new with ID set to the same fixed literal 'customer_id'. It's unlikely that's what you want; if customer_id is a column name from customers then it shouldn't be in single quotes.
As #mathguy suggested, long is not a sensible data type to use; you could use a CLOB but only really need a varchar2 here. So something more like this, where I've also switched to use an implicit cursor:
declare
l_stmt varchar2(4000);
begin
for i in (select id from temp_name)
loop
l_stmt := 'INSERT INTO temp_new(id) select '||i.id||' from customers';
dbms_output.put_line(i.id);
dbms_output.put_line(l_stmt);
execute immediate l_stmt;
end loop;
end;
/
db<>fiddle
The loop doesn't really make sense though; if your temp_name table had multiple rows with different column names, you'd try to insert the corresponding values from those columns in the customers table into multiple rows in temp_new, all in the same id column, as shown in this db<>fiddle.
I guess this is the starting point for something more complicated, but still seems a little odd.
I am trying to implement a statement level trigger to enforce the following "An applicant cannot apply for more than two positions in one day".
I am able to enforce it using a row level trigger (as shown below) but I have no clue how to do so using a statement level trigger when I can't use :NEW or :OLD.
I know there are alternatives to using a trigger but I am revising for my exam that would have a similar question so I would appreciate any help.
CREATE TABLE APPLIES(
anumber NUMBER(6) NOT NULL, /* applicant number */
pnumber NUMBER(8) NOT NULL, /* position number */
appDate DATE NOT NULL, /* application date*/
CONSTRAINT APPLIES_pkey PRIMARY KEY(anumber, pnumber)
);
CREATE OR REPLACE TRIGGER app_trigger
BEFORE INSERT ON APPLIES
FOR EACH ROW
DECLARE
counter NUMBER;
BEGIN
SELECT COUNT(*) INTO counter
FROM APPLIES
WHERE anumber = :NEW.anumber
AND to_char(appDate, 'DD-MON-YYYY') = to_char(:NEW.appDate, 'DD-MON-YYYY');
IF counter = 2 THEN
RAISE_APPLICATION_ERROR(-20001, 'error msg');
END IF;
END;
You're correct that you don't have :OLD and :NEW values - so you need to check the entire table to see if the condition (let's not call it a "constraint", as that term has specific meaning in the sense of a relational database) has been violated:
CREATE OR REPLACE TRIGGER APPLIES_AIU
AFTER INSERT OR UPDATE ON APPLIES
BEGIN
FOR aRow IN (SELECT ANUMBER,
TRUNC(APPDATE) AS APPDATE,
COUNT(*) AS APPLICATION_COUNT
FROM APPLIES
GROUP BY ANUMBER, TRUNC(APPDATE)
HAVING COUNT(*) > 2)
LOOP
-- If we get to here it means we have at least one user who has applied
-- for more than two jobs in a single day.
RAISE_APPLICATION_ERROR(-20002, 'Applicant ' || aRow.ANUMBER ||
' applied for ' || aRow.APPLICATION_COUNT ||
' jobs on ' ||
TO_CHAR(aRow.APPDATE, 'DD-MON-YYYY'));
END LOOP;
END APPLIES_AIU;
It's a good idea to add an index to support this query so it will run efficiently:
CREATE INDEX APPLIES_BIU_INDEX
ON APPLIES(ANUMBER, TRUNC(APPDATE));
dbfiddle here
Best of luck.
Your rule involves more than one row at the same time. So you cannot use a FOR ROW LEVEL trigger: querying on APPLIES as you propose would hurl ORA-04091: table is mutating exception.
So, AFTER statement it is.
CREATE OR REPLACE TRIGGER app_trigger
AFTER INSERT OR UPDATE ON APPLIES
DECLARE
cursor c_cnt is
SELECT 1 INTO counter
FROM APPLIES
group by anumber, trunc(appDate) having count(*) > 2;
dummy number;
BEGIN
open c_cnt;
fetch c_cnt in dummy;
if c_cnt%found then
close c_cnt;
RAISE_APPLICATION_ERROR(-20001, 'error msg');
end if;
close c_cnt;
END;
Obviously, querying the whole table will be inefficient at scale. (One of the reasons why triggers are not recommended for this sort of thing). So this is a situation in which we might want to use a compound trigger (assuming we're on 11g or later).
The idea is, I want to clone the record as a CLOB when it is updated.
Why do it in such a way?
There are two different applications A1 and A2, A1 is depended on by A2.
Based on A1 values, calculations are made for values for A2.
The A2 process runs just once per day to calculate the values, but for A1 every field in the TABLE_NAME in question can be altered several times a day and doesn't have a history.
The aim is to create a history which is a CLOB field in a table "NEW_TABLE" of automatic form.
Sorry for my English, but if something is not understandable I can rewrite the question
My Code Here:
CREATE or REPLACE TRIGGER TRIGGER_NAME
AFTER UPDATE
ON TABLE_NAME
FOR EACH ROW
DECLARE
row_record NEW_TABLE%rowtype;
c_xml CLOB;
FUNCTION GetXML(a_tablela varchar2, a_key_1 varchar2, a_key_2 varchar2)
RETURN CLOB
is
x_xml CLOB;
BEGIN
select dbms_xmlgen.getxml('select * from '||a_tablela||' where key_1 = '''||a_key_1||''' and key_2 = '''||a_key_2||'''') into x_xml from dual;
return x_xml;
END;
BEGIN
--** TABLE_NAME Automatically fetches all columns and transforms them to CLOB
c_xml := GetXML('TABLE_NAME', :new.key_1, :new.key_2);
if c_xml is not null then
row_record.TABLE_NAME :=c_xml;
end if;
INSERT INTO NEW_TABLE VALUES row_record;
EXCEPTION
when others then
raise_application_error(-20000,'ERROR: '||to_char(sqlcode));
END;
Now I get error:
ORA-04091: table TABLE_NAME is mutating, trigger/function may not see it.
when I get this record across SELECT statement.
How do I convert row into CLOB in the applied TRIGGER AFTER UPDATE ?
Thanks.
The reason you can't use a select statement is because you're in the trigger, and the table is changing, or 'mutating', as the error says. The only way you can get the data from the row that's being updated here is using new and old:
old.column1
new.column1
Old being the value of the column before the update, new being the value after the update.
Example:
CREATE or REPLACE TRIGGER TRIGGER_NAME
AFTER UPDATE
ON TABLE_NAME
FOR EACH ROW
BEGIN
l_string := 'This is the old value for column 1: ' || old.column1 || '. This is the new value: ' || new.column1;
dbms_output.put_line(l_string);
END;
You won't be able to use dbms_xmlgen because it uses a select statement, which throws the mutating error exception.
I'm not sure I perfectly understand what you're trying to do, but you should be able to build the CLOB yourself just by concatenating yourself with the column names. Like this:
CREATE or REPLACE TRIGGER TRIGGER_NAME
AFTER UPDATE
ON TABLE_NAME
FOR EACH ROW
BEGIN
l_clob := 'Column1 ' || old.column1 || ', Column2 ' || old.column2; --For as many columns as are in the table
--Now you have a clob with all the old values, insert it where you want it
END;
And then go from there. If you really want the XML format you can do that yourself as well, just concatenate the strings together.