I need to update a preexisting BLOB value in table using PL/SQL.
I'm dealing with poor table design, the column should be CLOB and that is not going to change.
The steps I want to perform:
1) select the BLOB
2) convert the BLOB to CLOB
3) modify the CLOB
3) convert the CLOB to BLOB
4) update the BLOB column with the new value
The 4th step I don't know how to do. I was hoping the BLOB could be updated directly but the only examples I find are reading a file into a blob column or using another programming language.
I understand your question, but i think there has to be another problem.
Solution
Just update it..
UPDATE myTable SET myBlobColumn = myBlob WHERE myCondition = 1;
Complete Example
DECLARE
myVarcharVar VARCHAR2(1000);
myClobVar CLOB;
myBlobVar BLOB;
BEGIN
EXECUTE IMMEDIATE 'TRUNCATE TABLE TTEST'; -- ensure out testdata will be correct.
INSERT INTO TTEST (myBlob, myClob, myVarchar) VALUES(utl_raw.cast_to_raw('1111'), '2222', '3333'); -- insert our data
-- Attention: ONLY ONE ROW => NO WHERE-CONDITIONS to simplify the code!
SELECT myVarchar INTO myVarcharVar FROM TTEST;
UPDATE TTEST SET myClob = myVarcharVar;
SELECT myClob INTO myClobVar FROM TTEST;
UPDATE TTest SET myBlob = utl_raw.cast_to_raw(myClobVar);
SELECT myBlob, myClob, myVarchar INTO myBlobVar, myClobVar, myVarcharVar FROM TTest;
dbms_output.put_line('Blob: ' || utl_raw.cast_to_varchar2(myBlobVar));
dbms_output.put_line('Clob: ' || myClobVar);
dbms_output.put_line('Varchar:' || myVarcharVar);
END;
update table_name set column_name = utl_raw.cast_to_raw ('value') where id = 'your_id';
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'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.
my Oracle SqlDeveloper (or Oracle Database?) doesn't know the :NEW keyword.
For instance, if I enter the following sample from Oracles website,
when I execute the "create or replace trigger" paragraph, a window "Enter bind variable" pops up and asks for the bind variable ":new".
Shouldn't this ":new" variable be predefined?
(Oracle SQL Developer 4.0.1.14, Oracle DB 11gR2, Windows)
drop table tab1;
create table tab1 (c1 clob);
insert into tab1 values ('testtext');
create or replace trigger trg1
before update on tab1
for each row
begin
dbms_output.put_line('Old value of CLOB column: '||:OLD.c1);
dbms_output.put_line('Proposed new value of CLOB column: '||:NEW.c1);
-- Previously, we couldn't change the new value for a LOB.
-- Now, we can replace it, or construct a new value using SUBSTR, INSTR...
-- operations for a CLOB, or DBMS_LOB calls for a BLOB.
:NEW.c1 := :NEW.c1 || to_clob('<hr><p>Standard footer paragraph.');
dbms_output.put_line('Final value of CLOB column: '||:NEW.c1);
end;
/
set serveroutput on;
update tab1 set c1 = '<h1>Different Document Fragment</h1><p>Different text.';
select * from tab1;
It turned out I just had to press "Apply" in the Bind dialog, and the trigger was created. Obviously a bug in SqlDeveloper. At least there is a workaround...
I added the 'REFERENCING' statement, and tested the code, seems to work just fine--- BTW, you can just turn DBMS output on in SQL dev w/o having to run the command..
CREATE OR REPLACE TRIGGER trg1
BEFORE UPDATE
ON tab1
REFERENCING NEW AS new OLD AS old
FOR EACH ROW
BEGIN
DBMS_OUTPUT.put_line ('Old value of CLOB column: ' || :old.c1);
DBMS_OUTPUT.put_line ('Proposed new value of CLOB column: ' || :new.c1);
-- Previously, we couldn't change the new value for a LOB.
-- Now, we can replace it, or construct a new value using SUBSTR, INSTR...
-- operations for a CLOB, or DBMS_LOB calls for a BLOB.
:new.c1 := :new.c1 || TO_CLOB ('<hr><p>Standard footer paragraph.');
DBMS_OUTPUT.put_line ('Final value of CLOB column: ' || :new.c1);
END;
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.
I have created the following object in oracle 11g.
CREATE OR REPLACE TYPE myObject as object(
fieldOne number,
fieldTwo number
);
And created a new table type of myObject;
CREATE OR REPLACE TYPE myTable IS TABLE OF myObject;
I would now like to create a new instance of myTable and add several hard-coded rows to myTable on the SQL Plus command line then pass the object to myProcedure as a parameter.
I have tried the following;
declare newTable myTable;
begin
select myObject(50,5) bulk collect into newTable from dual;
select myObject(40,7) bulk collect into newTable from dual;
myProcedure(newTable);
commit;
end;
Which sort-of works although the second select into statement overwrites the first.
My question is; how can I add multiple rows to newTable?
Many Thanks in Advance :)
declare
newTable myTable;
begin
newTable := myTable();
newTable.extend(2); -- The desired size of the collection
-- Oracle collections begin at index 1, not 0
newTable(1) := myObject(50, 5);
newTable(2) := myObject(40, 7);
myProcedure(newTable);
end;