I want to use cursor logic inside the data model's script in order to select some data from tables based on different conditions, but I can't do it from the data model's query script also I can't invoke already stored procedure from db, is there any better option to accomplish this
here are options that I have already tried but got some errors:
I have tried to create procedure and then invoke it from data model as well but it is not possible to call procedure from inside data model's script and i need to reflect procedure's data into data model structure, so i belive this scenario is not good for me.
I have used following solution Anonymous blocks (Procedural Call) data model in Oracle BI Publisher (Oracle Fusion):http://oracleappssolutiions.blogspot.com/2020/12/anonymous-blocks-procedural-call-data.html it is perfect when we need simple 'select' but can't run more complicated logic like this:
DECLARE
type refcursor is REF CURSOR;
xdo_cursor refcursor;
BEGIN
OPEN :xdo_cursor FOR
FOR c IN (select t.* from test t where t.VERSION=2) LOOP
FOR d in (select c.* from record d where CONNECT_BY_ISLEAF = 0 start with d.id. = c.id connect by prior d.id = c.id) loop
select * test
where id=d.id
end loop;
END LOOP;
END;
when i trying to run this i am getting similar errors:
Please share your thoughts/Ideas
Thanks
Try a Pipelined Table Function if you want to use a procedure to generate data.
https://docs.oracle.com/cd/B19306_01/appdev.102/b14289/dcitblfns.htm
If you can get away with just doing select statements with unions and where clause filters, that may be the cleanest way to go.
I'm not sure what the end goal is, but the grouping functionality for templates may help you. There's quite a bit of documentation in the user guides. look for for-each-group in the guide. It's used to take a single flat series of rows/elements, and then create a hierarchy of them, on the fly.
Related
First of all usually I am working with MSSQL. But I have a stored procedure in MSSQL, which I need to use in Oracle now and since I am absolutely new to Oracle I have no idea at all how to do it correct.
I needed to use user defined table types in my MS SQL stored procedure because I am using "logical" tables in my stored procedure, which I also need to pass them to a dynamic sql statement within this procedure (using column names of "physical" tables as variables/parameters).
I've started to add the oracle function in a package I made before for another function. It looks like
TYPE resultRec IS RECORD
(
[result columns]
);
TYPE resultTable IS TABLE OF resultRec;
Function MyFunctionName([A LOT PARAMETERS]) RETURN resultTable PIPELINED;
I also described the layout of the tables (the user defined table types in MSSQL), which I want to use within this function in this package header.
So far so good, but now I don't really know where I have to declare my table variables or user defined table types. I also tried to put them in the package header, but if I am trying to use these tables in the package body, where I am describing my function, Oracle tells met, that the table or view does not exist.
I also tried it to describe the tables within the package body or in the block of my function, which looks like that:
FUNCTION MyFunctionName
(
[MyParameters]
)
RETURN resultTable PIPELINED is rec resultrec;
TYPE tableVariableA IS TABLE OF tableRecA;
TYPE tableVariableB IS TABLE OF tableRecB;
BEGIN
INSERT INTO tableVariableA
SELECT ColumnA, ColumnB FROM physicalTable WHERE[...];
[A LOT MORE TO DO...]
END;
But in this case Oracle also tells me, that it doesn't know the table or view.
I also tried a few more things, but at the end I wasn't able to tell Oracle what table it should use...
I would appreciate every hint, which helps me to understand how oracle works in this case. Thanks a lot!
You can't insert into a collection (e.g. PL/SQL table). You can use the bulk collect syntax to populate the collection:
SELECT ColumnA, ColumnB
BULK COLLECT INTO tableVariableA
FROM physicalTable
WHERE [...];
However, you might want to check this is an appropriate approach, since SQL Server and Oracle differ quite a bit. You can't use PL/SQL tables in plain SQL (at least prior to 12c), even inside your procedure, so you might need a schema-level type rather than a PL/SQL type, but it depends what you will do next. You might not really want a collection at all. Trying to convert T-SQL straight to PL/SQL without understanding the differences could lead you down a wrong path - make sure you understand the actual requirement and then find the best Oracle mechanism for that.
First, I want to make it clear that the question is not about the materialized views feature.
Suppose, I have a table function that returns a pre-defined set of columns.
When a function call is submitted as
SELECT col1, col2, col3
FROM TABLE(my_tfn(:p1))
WHERE col4 = 'X';
I can evaluate the parameter and choose what queries to execute.
I can either open one of the pre-defined cursors, or I can assemble my query dynamically.
What if instead of evaluating the parameter I want to evaluate the text of the requesting query?
For example, if my function returns 20 columns but the query is only requesting 4,
I can assign NULLs to remaining 16 clumns of the return type, and execute fewer joins.
Or I can push the filter down to my dynamic query.
Is there a way to make this happen?
More generally, is there a way to look at the requesting query before exuting the function?
There is no robust way to identify the SQL that called a PL/SQL object.
Below is a not-so-robust way to identify the calling SQL. I've used code like this before, but only in special circumstances where I knew that the PL/SQL would never run concurrently.
This seems like it should be so simple. The data dictionary tracks all sessions and running SQL. You can find the current session with sys_context('userenv', 'sid'), match that to GV$SESSION, and then get either SQL_ID and PREV_SQL_ID. But neither of those contain the calling SQL. There's even a CURRENT_SQL in SYS_CONTEXT, but it's only for fine-grained auditing.
Instead, the calling SQL must be found by a string search. Using a unique name for the PL/SQL object will help filter out unrelated statements. To prevent re-running for old statements, the SQL must be individually purged from the shared pool as soon as it is found. This could lead to race conditions so this approach will only work if it's never called concurrently.
--Create simple test type for function.
create or replace type clob_table is table of clob;
--Table function that returns the SQL that called it.
--This requires elevated privileges to run.
--To simplify the code, run this as SYS:
-- "grant execute on sys.dbms_shared_pool to your_user;"
--(If you don't want to do that, convert this to invoker's rights and use dynamic SQL.)
create or replace function my_tfn return clob_table is
v_my_type clob_table;
type string_table is table of varchar2(4000);
v_addresses string_table;
v_hash_values string_table;
begin
--Get calling SQL based on the SQL text.
select sql_fulltext, address, hash_value
bulk collect into v_my_type, v_addresses, v_hash_values
from gv$sql
--Make sure there is something unique in the query.
where sql_fulltext like '%my_tfn%'
--But don't include this query!
--(Normally creating a quine is a challenge, but in V$SQL it's more of
-- a challenge to avoid quines.)
and sql_fulltext not like '%quine%';
--Flush the SQL statements immediately, so they won't show up in next run.
for i in 1 .. v_addresses.count loop
sys.dbms_shared_pool.purge(v_addresses(i)||', '||v_hash_values(i), 'C');
end loop;
--Return the SQL statement(s).
return v_my_type;
end;
/
Now queries like these will return themselves, demonstrating that the PL/SQL code was reading the SQL that called it:
SELECT * FROM TABLE(my_tfn) where 1=1;
SELECT * FROM TABLE(my_tfn) where 2=2;
But even if you go through all this trouble - what are you going to do with the results? Parsing SQL is insanely difficult unless you can ensure that everyone always follows strict syntax rules.
I have been googling for a while to find an alternative approach for returning a resultset rather than returning a ref cursor but failed to find it so. As i have done most of my development in sql server where we won't use cursors unless until it is necessary but i understand it differs from ref. cursor. But on top of that when we return a ref. cursor as an output from database it will become a connected architecture. So my dear Geeks can you answer/clear my confusions as mentioned below,
I want to understand which is the better way for returning a result set to our application (Ref. cursor or SELECT statement with all the joins or any other options)?
Is using ref. cursor is a connected /disconnected architecture?
Is using Select sql query is better for a disconnected approach?
Thanks in advance.
As usual, it depends on your needs.
Regarding connected /disconnected architecture it makes almost no difference. After your client application received the RefCursor and all rows are fetched (and preferably the cursor is closed) you can disconnect and reconnect from database the same way as using direct SELECT statement.
Consider following pseudo-code examples:
SELECT EMP_NAME, DEPT_NAME
FROM EMP
JOIN DEPT ON EMP_DEPT_ID = DEPT_ID
WHERE DEPT_ID = :d;
vs.
CREATE FUNCTION GetEmps(deptId IN NUMBER) RETURN SYS_REFCURSOR IS
res SYS_REFCURSOR;
BEGIN
OPEN res FOR
SELECT EMP_NAME, DEPT_NAME
FROM EMP
JOIN DEPT ON EMP_DEPT_ID = DEPT_ID
WHERE DEPT_ID = deptId;
RETURN res;
END;
My personal favorite is to prefer a RefCursors because:
With RefCursor client and server are more separated from each other, i.e. the client just has to know the function name and which attributes he receives (EMP_NAMEand DEPT_NAME), nothing else. He does not have to know the table names or any join condition. Developers of client and server can work more independently from each other.
With RefCursor you can implement fine-granularity security methods. You only have to do grant execute on GetEmps to ... and the client gets EMP_NAME and DEPT_NAME - no more, no less!
With direct SELECT you have to grant select on both tables, however then the client could also execute SELECT SALARY, EMP_NAME FROM EMP; for instance (unless you use the quite expensive VPD feature from Oracle). If you like you can log every single call of the function and add as many constraints as you like.
with RefCursor the client application (and not the server) can decide how many rows he like to fetch in order to optimize response times.
the basic difference is that when you are uncertain about the sql query you are going to execute at run time, then use ref cursor and you can use same ref cursor for different sql queries. for example
for query
select name,id,dob from table where id=:v_id;
here v_id is passed at run time, so we can use ref cursor. v_id varies at run time.
While the select statement is used in for each loop when we have small set of records. When we have large set of records we can use bulk collect with ref cursor and limit rows.
In Oracle, all DML statements are cursors. A cursor is simply a set of instructions used by the optimizer to get to the data.
In my Oracle-centric opinion, everything that is done in the database should be done in stored procedures, so that you have a central interface into the database - ie. if you had two applications updating/retrieving data to/from the same database, you'd only need one set of stored procs on the database, rather than replicating the logic twice in each application.
With that in mind, ref cursors are the way to go.
However, if you're not going down that route (boo! *{;-) ) there is little difference between a ref cursor and a straight select statement in terms of getting the data to the front end. How you call for the data will be different, of course, but it's the same thing to the database.
All a ref cursor does is basically hold a pointer to a cursor.
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.
First off, my background is in SQL Server. Using CTEs (Common Table Expressions) is a breeze and converting it to a stored procedure with variables doesn't require any changes to the structure of the SQL other than replacing entered values with variable names.
In Oracle PL/SQL however, it is a completely different matter. My CTEs work fine as straight SQL, but once I try to wrap them as PL/SQL I run into a host of issues. From my understanding, a SELECT now needs an INTO which will only hold the results of a single record. However, I am wanting the entire recordset of multiple values.
My apologies if I am missing the obvious here. I'm thinking that 99% of my problem is the paradigm shift I need to make.
Given the following example:
NOTE: I am greatly over simplifying the SQL here. I do know the below example can be done in a single SQL statement. The actual SQL is much more complex. It's the fundamentals I am looking for here.
WITH A as (SELECT * FROM EMPLOYEES WHERE DEPARTMENT = 200),
B as (SELECT * FROM A WHERE EMPLOYEE_START_DATE > date '2014-02-01'),
C as (SELECT * FROM B WHERE EMPLOYEE_TYPE = 'SALARY')
SELECT 'COUNTS' as Total,
(SELECT COUNT(*) FROM A) as 'DEPT_TOTAL',
(SELECT COUNT(*) FROM B) as 'NEW_EMPLOYEES',
(SELECT COUNT(*) FROM C) as 'NEW_SALARIED'
FROM A
WHERE rowcount = 1;
Now if I want to make this into PL/SQL with variables that are passed in or predefined at the top, it's not a simple matter of declaring the variables, popping values into them, and changing my hard-coded values into variables and running it. NOTE: I do know that I can simply change the hard-coded values to variables like :Department, :StartDate, and :Type, but again, I am oversimplifying the example.
There are three issues I am facing here that I am trying to wrap my head around:
1) What would be the best way to rewrite this using PL/SQL with declared variables? The CTEs now have to go INTO something. But then I am dealing with one row at a time as opposed to the entire table. So CTE 'A' is a single row at a time, and CTE B will only see the single row as opposed to all of the data results of A, etc. I do know that I will most likely have to use CURSORS to traverse the records, which somehow seems to over complicate this.
2) The output now has to use DBMS_OUTPUT. For multiple records, I will have to use a CURSOR with FETCH (or a FOR...LOOP). Yes?
3) Is there going to a big performance issue with this vs. straight SQL in regards to speed and resources used?
Thanks in advance and again, my apologies if I am missing something really obvious here!
First, this has nothing to do with CTEs. This behavior would be the same with a simple select * from table query. The difference is that with T-SQL, the query goes into an implicit cursor which is returned to the caller. When executing the SP from Management Studio this is convenient. The result set appears in the data window as if we had executed the query directly. But this is actually non-standard behavior. Oracle has the more standard behavior which might be stated as "the result set of any query that isn't directed into a cursor must be directed to variables." When directed into variables, then the query must return only one row.
To duplicate the behavior of T-SQL, you just have to explicitly declare and return the cursor. Then the calling code fetches from the cursor the entire result set but one row at a time. You don't get the convenience of Sql Developer or PL/SQL Developer diverting the result set to the data display window, but you can't have everything.
However, as we don't generally write SPs just to be called from the IDE, it is easier to work with Oracle's explicit cursors than SQL Server's implicit ones. Just google "oracle return ref cursor to caller" to get a whole lot of good material.
Simplest way is to wrap it into an implicit for loop
begin
for i in (select object_id, object_name
from user_objects
where rownum = 1) loop
-- Do something with the resultset
dbms_output.put_line (i.object_id || ' ' || i.object_name);
end loop;
end;
Single row query without the need to predefine the variables.