Problem Statement
I have a dynamic SQL which i need to store in a table ,but before
storing the sql i need to validate the sql with the list of columns
stored in another table.
Without executing the query , is it possible to find name of columns in the select ?
Approach1
Only option i can think of is ,try to use explain plan of the query and read the meta data in the data dictionaries table .But unfortunately i am not able to find any table with such data.Please let me know if you know such views?
Approach2
Use DBMS_SQL.DESCRIBE_COLUMNS package to find the column name ,but i believe this will execute the whole query.
You don't need to execute the query to get the column names, you just need to parse it; e.g. as a simple example:
set serveroutput on
declare
l_statement varchar2(4000) := 'select * from employees';
l_c pls_integer;
l_col_cnt pls_integer;
l_desc_t dbms_sql.desc_tab;
begin
l_c := dbms_sql.open_cursor;
dbms_sql.parse(c=>l_c, statement=>l_statement, language_flag=>dbms_sql.native);
dbms_sql.describe_columns(c=>l_c, col_cnt=>l_col_cnt, desc_t=>l_desc_t);
for i in 1..l_col_cnt loop
dbms_output.put_line(l_desc_t(i).col_name);
end loop;
dbms_sql.close_cursor(l_c);
exception
when others then
if (dbms_sql.is_open(l_c)) then
dbms_sql.close_cursor(l_c);
end if;
raise;
end;
/
which outputs:
EMPLOYEE_ID
FIRST_NAME
LAST_NAME
EMAIL
PHONE_NUMBER
HIRE_DATE
JOB_ID
SALARY
COMMISSION_PCT
MANAGER_ID
DEPARTMENT_ID
PL/SQL procedure successfully completed.
You can do whatever validation you need on the column names inside the loop.
Bear in mind that you'll only see (and validate) the column names or aliases for column expressions, which won't necessarily reflect the data that is actually being retrieved. Someone could craft a query that pulls any data from anywhere it has permission to access, but then gives the columns/expression aliases that are considered valid.
If you're trying to restrict access to specific data then look into other mechanisms like views, virtual private database, etc.
DBMS_SQL.PARSE will not execute a SELECT statement but it will execute a DDL statement. If the string 'select * from employees' is replaced by 'drop table employees' the code will fail but the table will still get dropped.
If you're only worried about the performance of retrieving the metadata then Alex Poole's answer will work fine.
If you're worried about running the wrong statement types then you'll want to make some adjustments to Alex Poole's answer.
It is surprisingly difficult to tell if a statement is a SELECT instead of something else. A simple condition checking that the string begins with select will work 99% of the time but getting from 99% to 100% is a huge amount of work. Simple regular expressions cannot keep up with all the different keywords, comments, alternative quoting format, spaces, etc.
/*comment in front -- */ select * from dual
select * from dual
with asdf as (select * from dual) select * from asdf;
((((((select * from dual))))));
If you need 100% accuracy I recommend you use my open source PLSQL_LEXER. Once installed you can reliably test the command types like this:
select
statement_classifier.get_command_name(' /*comment*/ ((select * from dual))') test1,
statement_classifier.get_command_name('alter table asdf move compress') test2
from dual;
TEST1 TEST2
----- -----
SELECT ALTER TABLE
Related
Ok I have seen a bunch of questions attempt to answer this but all the answers seem horribly complicated or don't actually answer the question.
Is there a way to simply do something like this:
DECLARE
v_some_variable VARCHAR2(10) := 'Find Me';
BEGIN
select column1, column2, column3
from someTable st
where st.columnTarget = v_some_variable
END;
And have this displayed in a grid?
This is so simple on SQL server and is maddeningly NOT simple in Oracle.
Every permutation or combination I try from various answers either does not work and gives an error, requires defining every column and datatype from the output prior to running the query or does not output to the grid and you have to roll your own text output. All of these are very poor solutions in my opinion. What am I missing? Oracle can't be this bad can it?
It is arguably possible to print query output from PL/SQL by returning a refcursor or printing it or something. Although like you, I don't find any of those solutions very easy or intuitive.
I do a lot of SQL development in Oracle, and generally - if you want to get a result grid back, don't use a PL/SQL block. Just use plain SQL statements.
select column1, column2, column3
from someTable st
where st.columnTarget = :v_some_variable; -- when you run this, it'll prompt for the value
If you don't like the prompt popup, you can also declare bind variables in SQL*Plus (the backend behind SQL Developer) like this:
var v_some_variable VARCHAR2(10)
exec :v_some_variable := 'Find Me';
select column1, column2, column3
from someTable st
where st.columnTarget = :v_some_variable;
If you run that as a script (F5), it won't prompt you for a value. Note that this still isn't using a PL/SQL block.
If you just want to use SQLPlus to write a query and execute it to see the results in a grid, then the simplest way to go is the following:
Start by defining the parameter:
define p = 1000;
Then you can use it:
select *
from table1 t1
join etc on etc.id = t1.etc_id
where etc.p = &p
You need to learn to do things the Oracle way, which is not the same as the SQL Server way. It's also incredibly simple in Oracle - if you know the way Oracle does it.
First we create the database table and add some data.
create table some_table (first varchar2(10), second varchar2(10));
insert into some_table values ('First', 'Find me');
Now for the PL/SQL.
declare
v_var varchar2(10);
v_var2 varchar2(10);
begin
v_var := 'Find me';
select first into v_var2 from some_table where second = v_var;
end;
/
Compare my PL/SQL with yours. Hint: Note that mine contains into
Refer to this db fiddle
I have a table that is filled with many data validation queries. For example a row:
SELECT end_time - start_time
FROM mt_process_status
WHERE process_id = <PROCESS_ID> AND ref_date = <REF_DATE>
I have to execute all these SQL statements filling the values within '<>' with run time values and check if the performance of the process has not changed.
Can this be done with a stored procedure? I want to understand what the solution would look like. Any links to documentation of this sort of thing, anything to guide me in the right direction.
Somewhere there's a bunch of analysts in your organization telling each other, "We've done the difficult stuff, we've defined the queries. All the database has to do is execute them, how hard can that be?" Answer: very hard.
Let's take the query you posted:
select end_time - start_time from mt_process_status where process_id = <PROCESS_ID> AND ref_date = <REF_DATE>
It's easy enough to use replace(the_str, '<PROCESS_ID>', 1234) to substitute a value. But for ref_date that's presumably a date, so it needs to be replace(the_str, '<REF_DATE>', 'date ''2017-01-01'''). Starting to get icky, and that's just handling literals. It will be even ickier when the substitution values are passed as parameters.
Of course I've made an assumption that PROCESS_ID is numeric. Maybe it isn't. Who can tell? Is there a data dictionary where these details are defined?
It would be easier if the query was defined with dynamic SQL placeholders:
select end_time - start_time from mt_process_status where process_id = :PROCESS_ID AND ref_date = :REF_DATE
Then you could forget about the replace and simply run
execute immediate the_str
using 1234, date '2017-01-01'
into whatever;
But you still need to know how many placeholders there are, in what order they occur and what datatype they are. It may feel like this is soft-coded and configurable but there is still a really hard dependency between the query and the program which calls it.
Plus you have lost the ability to do impact analysis. What queries will be affected when you change mt_process_status? Who can tell?
CREATE OR REPLACE PROCEDURE MY_PROC(g_id)
AS
l_query varchar2(1000);
l_duration number;
BEGIN
-- Get the query from the table
select query into l_query from my_table where id=g_id;
-- l_query contains "select end_time - start_time from mt_process_status where process_id = <PROCESS_ID> and ref_date = <REF_DATE>"
-- Put value to replace the tags (take care of code injection...)
l_query := REPLACE(l_query,'<PROCESS_ID>', something);
l_query := REPLACE(l_query,'<REF_DATE>', something_else);
EXECUTE IMMEDIATE lquery RETURN INTO l_duration;
-- Do what you have to do...
-- If you do a function, then you can:
-- RETURN l_duration;
END;
/
Your question is not clear. This is the answer to your question. Use variables in a procedure.
regards.
I would put the reference data in another table and do it as a join
As the title, I wanna create a procedure in Oracle/PLSQL to delete rows which share same values in some columns. I know how to implement it using Query, but how to do it using procedure? Do I have to use any loop? I am very new to PLSQL
Please help, thank you a lot!
If you want a simple procedure to delete from a particular table you can use the below piece of code:
CREATE OR REPLACE PROCEDURE DELETE_DUPLICATE AS
BEGIN
FOR I IN (SELECT TAB.A, TAB.B, MIN(ROWID) RID
FROM DUPLICATE_TABLE TAB
GROUP BY TAB.A, TAB.B
HAVING COUNT(*) > 1) LOOP
DELETE FROM DUPLICATE_TABLE TAB
WHERE I.RID <> TAB.ROWID
AND TAB.A = I.A
AND TAB.B = I.B;
COMMIT;
END LOOP;
END;
Here DUPLICATE_TABLE is the table having duplicate values. We are deleting rows having same values in columns A and B.
Hey. As per your question, although it is not advicable to create
procedure for this simpler task which can be easily done via Pure SQL.
But if its really imp to make it as a stored procedure then i would
suggest to use PURE SQL logic than using any kind of loop as there
will be Context Switching which will have a toll on the database.
Below is a snippet which i think will be useful also incorporated
Analytical function to suffice your issue. Let me know if it helps.
CREATE OR REPLACE PROCEDURE Dup_DELETE
AS
BEGIN
DELETE
FROM EMP
WHERE EMP.ROWID IN
-- Assuming that i am trying to segregate the duplicate values on Empno and ename
(SELECT A.ROWID
FROM
(SELECT ROW_NUMBER() OVER(PARTITION BY EMPNO,ENAME ORDER BY JOB DESC) RNK,
empno,
ename,
rowid
FROM EMP
)A
WHERE A.RNK <> 1
);
END;
Just put your SQL statement in a procedure. There's no rule that says you have to change the approach because it's PL/SQL. For example,
create or replace procedure dedupe_sometable
as
begin
delete sometable
where rowid in
( select lag(rowid) over (partition by id order by null)
from sometable );
end dedupe_sometable;
Add logging etc as needed.
(Ideally this would be within a package and not a standalone procedure.)
If you know how to do it in SQL, better to do it in sql. PL/SQL should be used only when you cannot write specific task in SQL statement or if there is performance issues in the query and can improve by writing the logic in PL/SQL (second scenario is very rare).
If you want to write PL/SQL procedure to parameterize so that any table can be passed to delete the duplicates from it, then it makes sense. You need to dynamically generate delete statement in the procedure and execute using execute immediate.
If your intention is to learn PL/SQL, then it is programming language and you need to spend some time as if you are learning new programming language.
It is not recommended to use plsql for something that can be done using plain sql.
Whenever you have a combination of sql and plsql, you are switching between sql and plsql engine. So it does not make sense to incur this overhead without proper requirement.
If for some reason there is still a need for doing this, you can atleast implement bulk delete to reduce some overhead. Please refer to the code below to find out how to do that -
DECLARE
TYPE t_del IS TABLE OF VARCHAR2(100);
l_del t_del;
CURSOR c IS
SELECT MIN(ROWID) RID
FROM test_tbl TAB
GROUP BY TAB.age, TAB.gender
HAVING COUNT(*) > 1;
BEGIN
OPEN c;
LOOP
FETCH c BULK COLLECT INTO l_del;
EXIT WHEN l_del.COUNT = 0;
FORALL i IN l_del.FIRST..l_del.last
DELETE FROM test_tbl WHERE ROWID = l_del(i);
END LOOP;
END;
select SRI_PACK_INDEX_VAL
from (select TABLE_NAME
from all_tables
where table_name like '%SE_RAO_INDEX_04_12_2015%');
Hi,
The above query is not working in oracle.Can anyone help me to solve this
You can't dynamically select from tables like that as Oracle's parser can't figure it out before fetch to know what tables it needs to read. If you want to do a dynamic fetch you need to do dynamic sql. Something like (forgive any minor syntax errors-I'm away from my database at the moment
declare
index_val number; -- i am assuming it is a number, change as appropriate
begin
-- I'm doing this in a loop if there are multiple tables that meet your name mask.
-- If there will only be one, then just select it into a variable and use it that way instead
for tab_name in (SELECT TABLE_NAME
from all_tables
where table_name like '%SE_RAO_INDEX_04_12_2015%')
loop
execute immediate 'select SRI_PACK_INDEX_VAL from '||tab_name.table_name
into index_val;
-- do your stuff with it
end loop;
end;
now, that works if the select only brings back one row. if you are bringing back multiple rows, then you have to handle it differently. In that case you will either want to EXECUTE IMMEDIATE a pl/sql block and embed your processing of the results there, or execute immediate bulk collect into an array, an example on how to do that is here.
select
extractvalue(
xmltype(
dbms_xmlgen.getxml(
'select sri_pack_index_val a from '||owner||'.'||table_name
)
), '/ROWSET/ROW/A'
) sri_pack_index_val
from all_tables
where table_name like '%SE_RAO_INDEX_04_12_2015%';
This query is based on a post from Laurent Schneider. Here's a SQLFiddle demonstration.
This is a neat trick to create dynamic SQL in SQL, but it has a few potential issues. It's probably not as fast as the typical dynamic SQL approach as shown by Michael Broughton. And I've ran into some weird bugs when trying to use this for large production queries.
I recommend only using this approach for ad hoc queries.
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.