I have very limited skill on pl-sql and I have a very complicated situation.
In mssql i have a procedure that returns a result set with varying number of columns from varying source tables depending on parameters provided.
In oracle i am having difficulty to create a proc which does the same.
I need to generate query inside, execute it and return the result.
I searched a lot and tried a lot of things. Now i now that the best way to do this is execute query into a cursor which i can not manage to do. Now all i can do is generate query and execute it - and have no visible result.
Any help ?
Thanks
Edit: Being more specific: how can i execute my dynamically generated query into a cursor or reutn with a local temporary table ?
Something like this?
create or replace procedure dynamic_cursor_demo
( p_some_expression in varchar2
, p_results out sys_refcursor )
as
begin
open p_results for
'select ' || p_some_expression || ' as demo from dual';
end dynamic_cursor_demo;
(If you have Oracle 12c you can also use implicit statement results. Examples in the docs.)
Related
I'm using Oracle Database 19c Enterprise Edition.
For various reasons, our core database devs write almost everything using procedures and not functions.
I thought it would be fun to wrap a procedure or two into a function that returns the one or two data items we need in our SQL.
Instead of creating a regular function like a normal person would do, I found that I could declare functions using the WITH statement right in my SQL.
This works great as I'll show in my first example below, but when I try to use it in a FOR LOOP cursor it gives me an ORA-06550 error (missing keyword) right after the WITH keyword.
Working SQL
with
function foobar(in_txt1 varchar2, in_txt2 varchar2) return varchar2 as
begin
return in_txt1 || in_txt2;
end foobar;
select foobar('foo','bar') mytxt from dual;
Broken SQL
begin
for cur in (
with
function foobar(in_txt1 varchar2, in_txt2 varchar2) return varchar2 as
begin
return in_txt1 || in_txt2;
end foobar;
select foobar('foo','bar') mytxt from dual
)
loop
dbms_ouput.put_line(cur.mytxt);
end loop;
end;
Oracle SQL Developer doesn't seem show any errors before I run the code. Does anyone know how to get this to work?
Yes, I know that I could just run the procedure inside the loop, but this is more for a learning experience rather than production code.
Edit: It works if I use dynamic SQL, but that's not something I like to use. I think this just isn't supported at this time. I'll close this question if others agree this can't be done yet.
Thanks!
i'am facing a problem while trying to make a conception for a school project.and i have two question.
1/
is it possible with oracle to do something like this : https://mariadb.com/kb/en/dynamic-columns/
2/
how can i make a modelisation for that with an MCD (method merise ).
thanks
Quote from your link: "It works by storing a set of columns in a blob and having a small set of functions to manipulate it.". I don't see an obvious reason why you couldn't write something similar for Oracle (or any other relational database).
Alternatively, take a look at EAV, which is a more traditional solution for dynamic columns.
Sorry, I'm not familiar with Merise.
1/ Oracle is not made for creating dynamic columns, but you can do it by using PL/SQL functions (but not while querying with SQL):
create or replace procedure add_table_column(table_name varchar2, column_name varchar2, column_type varchar2)
is
v_script varchar2(4000);
begin
v_script := 'alter table '||table_name||' add '||column_name||' '||column_type;
execute immediate v_script;
end;
/
You can call it this way:
begin
add_table_column('toto','test','number');
end;
/
2/ Merise method is not made for "dynamic objects" as you must begin with a complete data dictionary.
How is your object dynamic, and why do you have to add columns?
You can always get a solution to work by using "regular" tables and relationships.
It sounds like you should start by analyzing the technical implementation in mind. MERISE says to analyze your data model first and start to think about technical solutions after.
I have many PL/SQL functions and procedures that execute dynamic sql.
Is it possible to extract the parsed statements and dbms_output as an debugging aid ?
What I really want is to see the parsed sql (sql statement with substituted parameters).
Example:
I have a dynamic SQL statement like this
SQ:='SELECT :pComno as COMNO,null t$CPLS,t$CUNO,t$cpgs,t$stdt,t$tdat,t$qanp,t$disc,:cS Source FROM BAAN.TTDSLS031'||PCOMNO --1
|| ' WHERE' ||' TRIM(T$CUNO)=trim(:CUNO)' --2
|| ' AND TRIM(T$CPGS)=trim(:CPGS)' --3
|| ' AND T$QANP = priceWorx.fnDefaultQanp ' --4
|| ' AND priceWorx.fdG2J(sysdate) between priceWorx.fdG2J(t$stdt) and priceWorx.fdG2J(t$tdat)' --5
|| ' AND rownum=1 order by t$stdt';--6
execute immediate SQ into R using
PCOMNO,'C' --1
,PCUNO-- 2
,PCPGS;-- 3
What will be the statement sent to the server ?
You can display the bind variables associated with a SQL statement like this:
select v$sql.sql_text
,v$sql_bind_capture.*
from v$sql_bind_capture
inner join v$sql on
v$sql_bind_capture.hash_value = v$sql.hash_value
and v$sql_bind_capture.child_address = v$sql.child_address
--Some unique string from your query
where lower(sql_text) like lower('%priceWorx.fdG2J(sysdate)%');
You probably would like to see the entire query, with all the bind variables replaced by their actual values. Unfortunately, there's no easy way to get exactly what you're looking for, because of the following
issues.
V$SQL_BIND_CAPTURE doesn't store all of the bind variable information. The biggest limitation is that it only displays data "when the bind variable is used in the WHERE or HAVING clauses of the SQL statement."
Matching the bind variable names from the bind capture data to the query is incredibly difficult. It's easy to get it working 99% of the time, but that last 1% requires a SQL and PL/SQL parser, which is basically impossible.
SQL will age out of the pool. For example, if you gather stats on one of the relevant tables, it may invalidate all queries that use that table. You can't always trust V$SQL to have your query.
Which means you're probably stuck doing it the ugly way. You need to manually store the SQL and the bind variable data, similar to what user1138658 is doing.
You can do this with the dbms_output package. You can enable and disable the debug, and get the lines with get_line procedure.
I tested with execute immediate, inserting in a table and it works.
I recently answered another question with a example of using this.
One possible solution of this is to create a table temp(id varchar2,data clob); in your schema and then put the insert statement wherever you want to find the parsed key
insert into temp values(seq.nextval,v_text);
For example
declare
v_text varchar2(2000);
begin
v_text:='select * from emp'; -- your dynamic statement
insert into temp values(seq.nextval,v_text); --insert this script whenever you want to find the actual query
OPEN C_CUR FOR v_text;
-----
end;
Now if you see the table temp, you'll get the data for that dynamic statement.
The dynamic request looks like this:
request := 'select * from ' || param_table_name || ' where ' || column_name_list;
Then I do:
open cur1 for request;
The exact type of record fetched via cur1 isn't known until runtime, because it should impose no restrictions on whatever table this procedure is applied to. But then, how do I iterate through what the query returns?
PL/SQL cursors cannot work with columns that aren't known a compile time.
To only way to work with fully dynamic queries in PL/SQL is by using the PL/SQL package DBMS_SQL.
Update:
Oracle has a comprehensive description of the DBMS_SQL package with many examples.
This question is similar to a couple others I have found on StackOverflow, but the differences are signficant enough to me to warrant a new question, so here it is:
I want to obtain a result set from dynamic SQL in Oracle and then display it as a result set in a SqlDeveloper-like tool, just as if I had executed the dynamic SQL statement directly. This is straightforward in SQL Server, so to be concrete, here is an example from SQL Server that returns a result set in SQL Server Management Studio or Query Explorer:
EXEC sp_executesql N'select * from countries'
Or more properly:
DECLARE #stmt nvarchar(100)
SET #stmt = N'select * from countries'
EXEC sp_executesql #stmt
The question "How to return a resultset / cursor from a Oracle PL/SQL anonymous block that executes Dynamic SQL?" addresses the first half of the problem--executing dynamic SQL into a cursor. The question "How to make Oracle procedure return result sets" provides a similar answer. Web search has revealed many variations of the same theme, all addressing just the first half of my question. I found this post explaining how to do it in SqlDeveloper, but that uses a bit of functionality of SqlDeveloper. I am actually using a custom query tool so I need the solution to be self-contained in the SQL code. This custom query tool similarly does not have the capability to show output of print (dbms_output.put_line) statements; it only displays result sets. Here is yet one more possible avenue using 'execute immediate...bulk collect', but this example again renders the results with a loop of dbms_output.put_line statements. This link attempts to address the topic but the question never quite got answered there either.
Assuming this is possible, I will add one more condition: I would like to do this without having to define a function or procedure (due to limited DB permissions). That is, I would like to execute a self-contained PL/SQL block containing dynamic SQL and return a result set in SqlDeveloper or a similar tool.
So to summarize:
I want to execute an arbitrary SQL statement (hence dynamic SQL).
The platform is Oracle.
The solution must be a PL/SQL block with no procedures or functions.
The output must be generated as a canonical result set; no print statements.
The output must render as a result set in SqlDeveloper without using any SqlDeveloper special functionality.
Any suggestions?
The closest thing I could think of is to create a dynamic view for which permission is required. This will certainly involve using a PL/SQL block and a SQL query and no procedure/function. But, any dynamic query can be converted and viewed from the Result Grid as it's going to be run as a select query.
DEFINE view_name = 'my_results_view';
SET FEEDBACK OFF
SET ECHO OFF
DECLARE
l_view_name VARCHAR2(40) := '&view_name';
l_query VARCHAR2(4000) := 'SELECT 1+level as id,
''TEXT''||level as text FROM DUAL ';
l_where_clause VARCHAR2(4000):=
' WHERE TRUNC(1.0) = 1 CONNECT BY LEVEL < 10';
BEGIN
EXECUTE IMMEDIATE 'CREATE OR REPLACE VIEW '
|| l_view_name
|| ' AS '
|| l_query
|| l_where_clause;
END;
/
select * from &view_name;
You seem to be asking for a chunk of PL/SQL code that will take an arbitrary query returning result set of undetermined structure and 'forward/restructure' that result set in some way such that is can easily be rendered by some "custom GUI tool".
If so, look into the DBMS_SQL for dynamic SQL. It has a DESCRIBE_COLUMNS procedure which returns the columns from a dynamic SELECT statement. The steps you would need are,
Parse the statement
Describe the result set (column names and data types)
Fetch each row, and for each column, call the datatype dependent function to return that value into a local variable
Place those local variables into a defined structure to return to the calling environment (eg consistent column names [such as col_1, col_2] probably all of VARCHAR2)
As an alternative, you could try building the query into an XMLFOREST statement, and parse the results out of the XML.
Added :
Unlike SQL Server, an Oracle PL/SQL call will not 'naturally' return a single result set. It can open up one or more ref cursors and pass them back to the client. It then becomes the client's responsibility to fetch records and columns from those ref cursors. If your client doesn't/can't deal with that, then you cannot use a PL/SQL call.
A stored function can return a pre-defined collection type, which can allow you to do something like "select * from table(func_name('select * from countries'))". However the function cannot do DML (update/delete/insert/merge) because it blows away any concept of consistency for that query. Plus the structure being returned is fixed so that
select * from table(func_name('select * from countries'))
must return the same set of columns (column names and data types) as
select * from table(func_name('select * from persons'))
It is possible, using DBMS_SQL or XMLFOREST, for such a function to take a dynamic query and restructure it into a pre-defined set of columns (col_1, col_2, etc) so that it can be returned in a consistent manner. But I can't see what the point of it would be.
Try try these.
DECLARE
TYPE EmpCurTyp IS REF CURSOR;
v_emp_cursor EmpCurTyp;
emp_record employees%ROWTYPE;
v_stmt_str VARCHAR2(200);
v_e_job employees.job%TYPE;
BEGIN
-- Dynamic SQL statement with placeholder:
v_stmt_str := 'SELECT * FROM employees WHERE job_id = :j';
-- Open cursor & specify bind argument in USING clause:
OPEN v_emp_cursor FOR v_stmt_str USING 'MANAGER';
-- Fetch rows from result set one at a time:
LOOP
FETCH v_emp_cursor INTO emp_record;
EXIT WHEN v_emp_cursor%NOTFOUND;
END LOOP;
-- Close cursor:
CLOSE v_emp_cursor;
END;
declare
v_rc sys_refcursor;
begin
v_rc := get_dept_emps(10); -- This returns an open cursor
dbms_output.put_line('Rows: '||v_rc%ROWCOUNT);
close v_rc;
end;
Find more examples here. http://forums.oracle.com/forums/thread.jspa?threadID=886365&tstart=0
In TOAD when executing the script below you will be prompted for the type of v_result. From the pick list of types select cursor, the results are then displayed in Toad's data grid (the excel spreadsheet like result). That said, when working with cursors as results you should always write two programs (the client and the server). In this case 'TOAD' will be the client.
DECLARE
v_result sys_refcursor;
v_dynamic_sql VARCHAR2 (4000);
BEGIN
v_dynamic_sql := 'SELECT * FROM user_objects where ' || ' 1 = 1';
OPEN :v_result FOR (v_dynamic_sql);
END;
There may be a similar mechanism in Oracle's SQL Developer to prompt for the binding as well.