I've heard that it's a good practice to define your records in PL/SQL by using the %ROWTYPE attribute. This saves typing and allows your package to continue functioning even when a column is added or deleted. (Correct me if I'm wrong!)
However, when I am fetching from a cursor that involves a join, I find that I have to fetch into a programmer-defined record that includes a (quite-possibly long) hand-written list of every column returned by the join.
So my question is:
Is it possible to fetch into nested records, or fetch into a list of records, or do something to avoid such an ugly kludge? Everything I've tried leads to an error about the record not matching what's being returned by the cursor.
Returning the result of a join using a cursor seems like such a common use-case to me that it's strange that nothing related to this comes up in a search.
Thank you.
You can user cursor%rowtype.
Sample:
declare
cursor c_c is
select emp.*, dept.* -- use aliasses if columns have same name
from emp
, dept; -- for sample no join condition
r_c c_c%rowtype;
begin
for r_c in c_c loop -- with for loop even the definition of r_c is not needed.
...
end loop;
end;
/
Why even bother with the cursor declaration?
This is equivalent.
begin
for r_c in (select emp.*, dept.* from emp, dept) loop
...
end loop;
end;
I see in your comment you mention this. But I see the explicit cursor syntax used so much, i think it's important to show.
Related
I have below query which I am trying to write in a procedure after begin clause. I dont want to use it as a cursor because of some dependency.
I want to make my db link dynamic instead of hardcoding it and for this reason i put my entire for loop in variable. If i take the variable out then my procedure is working fine. I dont want to change logic of my code while trying to make dblink dynamic.
But this part of loop is not working and throwing an error as
encounter the symbol end of the file when expecting one of the following:
PROCEDURE TMP_CHECK
IS
open CS for NESS_QUERY;
loop
fetch CS into REC;
exit when CS%notfound;
INSERT INTO TMP_Data(ID,NAME,ID_TST,CHK_DATE,VALUE,CHECK,SOURCE) VALUES
(IN_SEQ_NO,DB_NAME,DB_ID,REC.DAY_ID,REC.nb_ord,'ORDS','LEOSOFT');
COMMIT;
END LOOP;
CLOSE CS;
END LOOP;
END;
Dynamic SQL is hard because it turns compilation errors into runtime errors. It looks like your query has several compilation errors: duplicate table aliases, out-of-scope alias references, cross joins between the remote tables (unless that is deliberate, in which case yuck!). So the first thing to do is get the query running as straight SQL, only then make it dynamic.
Also don't include commented code in your template SQL. Things are already hard enough, why make them even harder by doing stuff like this?
ORDER BY
-- TE.market asc,
-- TE.entity asc,
TE.dayiid ASC)'
So, now we've got that out of the way let's look at the logic of what you're trying to do. We cannot drop dynamic segments of PL/SQL into a program. This just won't work ...
LQUERY='
FOR REC IN(
SELECT
... because you have not written a complete PL/SQL statement. But there is a way to do what you want: use a cursor variable. We can open a ref cursor for static and dynamic queries. Find out more.
The following is for illustrative purposes only: you haven't explained your business logic, so this is not necessarily the best way of doing things. But it should solve your immediate problem:
declare
....
l_order number;
l_dayiid number;
l_ety_id number;
rc sys_refcursor;
begin
...
FOR IIS_DB IN C_DB
LOOP
IN_DB_LINK:=LEO_DB.DATABASE_LINK;
IN_DAY:=LEO_DB.DAY_ID;
open rc for
'SELECT order,dayiid,ety_id
from ...
ORDER BY TE.dayiid ASC)';
loop
fetch rc into l_order, l_dayiid, l_ety_id;
exit when rc%notfound;
...
end loop;
close rc;
" PLS-00487: Invalid reference to variable 'REC'"
I think your problem is this:
fetch CS into REC;
You have defined REC as a string but clearly it should be a record type, which needs to match the projection of the query you're fetching. So you need to define something like this:
Type rec_t is record (
nb_ord number,
day_id number,
entity number
);
REC rec_t;
Now you can fetch a record into REC and reference its attributes.
Incidentally the nvl() you've written to supply NB_ORD is wrong. The first argument is the one you are testing for null: 500 will never be null so that's what you'll get for every row. You need to swap the parameters round.
Why Oracle made "where current of" syntax when you can use "rowid"? Example:
BEGIN
FOR rec IN (SELECT t.column1, t.rowid rid FROM test_table) LOOP
UPDATE test_table tb SET column1 = some_function(rec.column1) WHERE tb.rowid = rec.rid;
END LOOP;
COMMIT;
END;
DECLARE
CURSOR cur IS SELECT t.column1 FROM test_table;
param1 test_table.column1%TYPE;
BEGIN
LOOP
FETCH cur INTO param1;
UPDATE test_table tb SET tb.column1 = some_function(param1) WHERE CURRENT OF cur;
EXIT WHEN cur%NOTFOUND;
END LOOP;
COMMIT;
END;
Where Current Of is used to identify LAST FETCHED ROW in cursor. It's more safe, because You have 100% confidence, that f.e. You updating LAST FETCHED ROW from curosr. With Rowids there's danger, because it's really easy to mess up something.
Using WHERE CURRENT OF clause without having FOR UPDATE clause mentioned in your SELECT statement could be risky. Reason behind that is when you are not applying FOR UPDATE clause then you are not exclusively placing Row level lock to those rows which you are intending to update in the following UPDATE DML. And hence it opens an opportunity for outside world of violating data consistency i.e. some other user from different session may be looking to UPDATE same rows of your targeted table.
Also, in you learn more about WHERE CURRENT OF clause you will notice that during this clause Oracle internally makes use of ROWID's only to reach/identify the rows which needs to be updated.
Hope it helps !! Happy Programming
How do I perform a select on a rather simple view in oracle pl/sql using a stored procedure.
Lets say the view looks like this:
FirstName LastName
-------- -------
Bob Jones
James Kay
etc...
To me its should be so simple:
Procedure SuperSimple()
begin
select FirstName, LastName from SuperSimple
end
However I've been told that this will not work.
So I tried to use a PL/SQL cursor. Still scratching my head trying to figure out why I am using cursors. But it appears to be necessary in 11g.
Procedure AlphaPrime(Results OUT Ref CURSOR) IS
begin
OPEN Results for
select FirstName, LastName from SuperSimple;
end;
Now I was hoping this would work but I'm doing something like this with select statements and it appears to be not working.
Do I also need to add a fetch and another open and a close command to make this thing work? What is the idea behind all this? I've noticed that trying to find info on how to add a very simple select statemetn to a procedure appears to be missing from most documentation that I've read. Is there a reason for this like its too simple to add a select statement to a procedure as it would be better to add it to a view. Something along those lines.
The problem I'm having is I want to start out really simple and tac on a little bit more complexity to the sproc over time... where time ~ 1 to 2 hours. Can someone point me to some docs in Oracle PL/SQL that shows how to add a simple table or view. Also If the permissions for a specific view or table is not allowed does it just fail for that user or does it give an empty result set.
It is not clear from your question what are you intending to do with the query result inside your procedure. So here I make some examples with dbms_output which prints to screen out some message and data from your query. Probably you will replace it with your logic.
Let's have some view (actually it doesn't matter here whether you are querying view or table, but I would stick to your question)
create table some_simple_table(firstname varchar2(30), lastname varchar2(30));
/
create or replace view supersimple_view as select firstname, lastname, 'whatever1' whatever from some_simple_table;
/
The following code does select into variable, this will work only if query returns exactly one row.
create or replace procedure supersimple1 is
vfirstname supersimple_view.firstname%type;
vwhatever supersimple_view.whatever%type;
vsupersimple supersimple_view%rowtype;
begin
select firstname, whatever into vfirstname, vwhatever from supersimple_view;
dbms_output.put_line('I''m doing some logic with this'|| vwhatever );
select * into vsupersimple from supersimple_view;
dbms_output.put_line('I''m doing some logic with this'|| vsupersimple.firstname);
end;
/
Perhaps you can implement implicit cursor loop through results and do some logic.
create or replace procedure supersimple2 is
begin
for rec in (select * from supersimple_view)
loop
dbms_output.put_line('I''m doing some logic with this record '|| rec.firstname);
end loop;
end;
/
Another option is cursor (particularly in case when you will reuse the same select) loop through results and do some logic.
create or replace procedure supersimple3 is
cursor cur is (select * from supersimple_view);
vsupersimple cur%rowtype;
begin
open cur ;
loop
FETCH cur INTO vsupersimple;
EXIT WHEN cur%NOTFOUND;
dbms_output.put_line('I''m doing some logic with this record '|| vsupersimple.firstname);
end loop;
close cur;
end;
/
You can fetch result of your query to collection
create or replace procedure supersimple4 is
type supersimple_colt is table of supersimple_view%rowtype index by pls_integer;
vsupersimple_col supersimple_colt;
begin
select * bulk collect into vsupersimple_col from supersimple_view ;
for i in 1 .. vsupersimple_col.count
loop
dbms_output.put_line('I''m doing some logic with this record '|| vsupersimple_col(i).firstname);
end loop;
end;
/
Instead of PL/SQL type declared in supersimple4 you can create standalone database SQL types and used them to fetch results into. This aproach gives you various features like: possibility to query collection in select statement in table like fashion, converting it to xml by xmltype, etc.
I think I found the answer. For each column that is selected on, it needs a view or table column type, which is sort of like the list of parameters used for the final output. That way when you declare on it you can better know what you are getting, which sorta makes sense.
So if you have two tables or views which were used to generate the output columns, you would need both of those tables or views in your descriptive OUT variables to describe better what you are outputting in the final output result.
See this link.
I'm taking an educated guess with this next part as I'm just beginning to understand it:
This query should work. But if its not it may be due to insuffiecient priviledges. Try a table that you know you have access and select it in a procedure in debug mode. Then try a view.
Procedure AlphaPrime(Results OUT Ref CURSOR) IS
begin
OPEN Results for
select FirstName, LastName from SuperSimple;
end;
Also there is a possibility with Debug mode and your assigned user roles that you may have insufficient priviledges to debug all the objects in the view and they may not be accessible. Sometimes you can just hit the "Ignore" button in Toad to skip over debugging inside a stored procedure. Also you may have priveledges to view the results the object just not view its structure which may also give you insufficient priviledges errors. Again just ignore them to skip over those types of issues and see the results while in debug mode. If you don't debug this, then you should not see any errors and just get the results.
I have a cursor which is
CURSOR B_CUR IS select DISTINCT big_id from TEMP_TABLE;
This would return multiple values. Earlier it was being used as
FOR b_id IN B_CUR LOOP
select s.col1, s.col2 INTO var1, var2 from sometable s where s.col3 = b_id.col1;
END LOOP;
Earlier it was certain that the inner select query would always return 1 row. Now this query can return multiple rows. How can I change this logic?
I was thinking to create a nested cursor which will fetch into an array of record type (which i will declare) but I have no idea how nested cursor would work here.
My main concern is efficiency. Since it would be working on millions of records per execution. Could you guys suggest what would be the best approach here?
Normally, you would just join the two tables.
FOR some_cursor IN (SELECT s.col1,
s.col2
FROM sometable s
JOIN temp_table t ON (s.col3 = t.col1))
LOOP
<<do something>>
END LOOP
Since you are concerned about efficiency, however
Is TEMP_TABLE really a temporary table? If so, why? It is exceedingly rare that Oracle actually needs to use temporary tables so that leads me to suspect that you're probably doing something inefficient to populate the temporary table in the first place.
Why do you have a cursor FOR loop to process the data from TEMP_TABLE? Row-by-row processing is the slowest way to do anything in PL/SQL so it would generally be avoided if you're concerned about efficiency. From a performance standpoint, you want to maximize SQL so that rather than doing a loop that did a series of single-row INSERT or UPDATE operations, you'd do a single INSERT or UPDATE that modified an entire set of rows. If you really need to process data in chunks, that's where PL/SQL collections and bulk processing would come in to play but that will not be as efficient as straight SQL.
Why do you have the DISTINCT in your query against TEMP_TABLE? Do you really expect that there will be duplicate big_id values that are not erroneous? Most of the time, people use DISTINCT incorrectly either to cover up problems where data has been joined incorrectly or where you're forcing Oracle to do an expensive sort just in case incorrect data gets created in the future when a constraint would be the more appropriate way to protect yourself.
FOR b_id IN B_CUR LOOP
for c_id in (select s.col1, s.col2 INTO var1, var2 from sometable s where s.col3 = b_id.col1)loop
......
end loop;
END LOOP;
How to query bulk collection? If for example I have
select name
bulk collect into namesValues
from table1
where namesValues is dbms_sql.varchar2_table.
Now, I have another table XYZ which contains
name is_valid
v
h
I want to update is_valid to 'Y' if name is in table1 else 'N'. Table1 has 10 million rows. After bulk collecting I want to execute
update xyz
set is_valid ='Y'
where name in namesValue.
How to query namesValue? Or is there is another option. Table1 has no index.
please help.
As Tom Kyte (Oracle Corp. Vice President) says:
My mantra, that I'll be sticking with thank you very much, is:
You should do it in a single SQL statement if at all possible.
If you cannot do it in a single SQL Statement, then do it in PL/SQL.
If you cannot do it in PL/SQL, try a Java Stored Procedure.
If you cannot do it in Java, do it in a C external procedure.
If you cannot do it in a C external routine, you might want to
seriously think about why it is you need to do it…
think in sets...
learn all there is to learn about SQL...
You should perform your update in SQL if you can. If you need to add an index to do this then that might be preferable to looping through a collection populated with BULK COLLECT.
If however, this is some sort of assignment....
You should specify it as such but here's how you would do it.
I have assumed that your DB server does not have the capacity to hold 10 million records in memory so rather than BULK COLLECTing all 10 million records in one go I have put the BULK COLLECT into a loop to reduce your memory overheads. If this is not the case then you can omit the bulk collect loop.
DECLARE
c_bulk_limit CONSTANT PLS_INTEGER := 500000;
--
CURSOR names_cur
IS
SELECT name
FROM table1;
--
TYPE namesValuesType IS TABLE OF table1.name%TYPE
INDEX BY PLS_INTEGER;
namesValues namesValuesType;
BEGIN
-- Populate the collection
OPEN name_cur;
LOOP
-- Fetch the records in a loop limiting them
-- to the c_bulk_limit amount at a time
FETCH name_cur BULK COLLECT INTO namesValues
LIMIT c_bulk_limit;
-- Process the records in your collection
FORALL x IN INDICES OF namesValues
UPDATE xyz
SET is_valid ='Y'
WHERE name = namesValue(x)
AND is_valid != 'Y';
-- Set up loop exit criteria
EXIT WHEN namesValues.COUNT < c_bulk_limit;
END LOOP;
CLOSE name_cur;
-- You want to update all remaining rows to 'N'
UPDATE xyz
SET is_valid ='N'
WHERE is_valid IS NULL;
EXCEPTION
WHEN others
THEN
IF name_cur%ISOPEN
THEN
CLOSE name_cur;
END IF;
-- Re-raise the exception;
RAISE;
END;
/
Depending upon your rollback segment sizes etc. you may want to issue interim commits within the bulk collect loop but be aware that you will not then be able to rollback these changes. I deliberately haven't added any COMMITs to this so you can choose where to put them to suit your system.
You also might want to change the size of the c_bulk_limit constant depending upon the resources available to you.
Your update will still cause you problems if the xyz table is large and there is no index on the name column.
Hope it helps...
"Table1 has no index."
Well there's your problem right there. Why not? Put an index on TABLE1.NAME and use a normal SQL UPDATE to amend the data in XYZ.
Trying to solve this problem with bulk collect is not the proper approach.