I'm designing an HTML report that effectively extracts columns from a single table
The number of columns in this table is quite large, and I would like some way to configure the application to say which columns to display. Note: This is not a per-user setting.
Lets say I have the main table:
MAIN_TABLE
id
first_name
last_name
weight
height
attribute_4
attribute_5
attribute_6
...
attribute_99
I was thinking of a table like
MAIN_TABLE_DISPLAY
column_name
display
Or perhaps
MAIN_TABLE_DISPLAY
display_id
display_first_name
display_last_name
display_weight
display_height
display_attribute_4
display_attribute_5
display_attribute_6
...
display_attribute_99
But I would like to perform an efficient join.
Any suggestions?
Thanks.
Dynamic column inclusion/exclusion == dynamic SQL.
This solution might give you some ideas.
http://tkyte.blogspot.com/2006/01/i-like-online-communities.html - he passes a ref_cursor to a function that returns a CLOB that is fully formatted HTML table with full resultset of that ref_cursor. All in less than 100 lines.
Have you thought about using a view? Your application can pull it's data from there, and to change which columns you're showing, change the view. You would have to change the presentation side of things to account for the different columns also.
As jva said, you'll need to use dynamic SQL. Something like this (with the appropriate bug fixes) should do it:
type column_table is table of varchar2(30);
function table_as_html(table_name varchar2, columns column_table) return clob is
sql_query varchar2(32767);
sql_cursor sql_refcursor;
html_row clob;
html_text clob;
begin
sql_query := 'select ''<tr>';
for column in 1 .. columns.count loop
sql_query := sql_query||'||''<td>''||'||columns(column)||'||''</td>'''
end loop;
sql_query := sql_query||'||''</tr>'' from '||table_name;
open sql_cursor for sql_query;
loop
fetch sql_cursor into html_row;
exit when sql_cursor%notfound;
html_text := html_text||html_row||chr(10);
end loop;
close sql_cursor;
return html_text;
end;
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 have a procedure in which I want to fetch all records from cte into Names variable. But this code is not writing into names from CTE. How can I fetch records into names so that I can later loop through names and get content of field_name?
CREATE OR REPLACE PROCEDURE sp_market
IS
Names VARCHAR2(32767);
BEGIN
WITH CTE(sqql) As
(
SELECT field_name sqql FROM pld_medicare_config
)
SELECT sqql into Names from CTE;
END sp_market;
SELECT sqql into Names from CTE;
You are assigning multiple rows returned from table to a variable, which will fail.
You could simply use a CURSOR FOR LOOP which will create an implicit cursor and you can loop through the names:
CREATE OR REPLACE PROCEDURE sp_market IS
BEGIN
FOR i IN (
SELECT field_name
FROM pld_medicare_config
)
LOOP
-- Your logic goes here
dbms_output.put_line(i.field_name);
END LOOP;
END;
/
I think your best bet is to create a associative array and use BULK COLLECT to populate the table. In its simplest form, the code would look like this:
CREATE OR REPLACE PROCEDURE sp_market IS
TYPE lt_names IS TABLE OF VARCHAR2(32767) INDEX BY PLS_INTEGER;
l_tNames lt_names;
BEGIN
SELECT field_name
BULK COLLECT INTO l_tNames
FROM pld_medicare_config
IF l_tNames.COUNT() > 0 THEN
FOR i IN l_tNames.FIRST..l_tNames.LAST LOOP
NULL; --REPLACE WITH YOUR LOGIC
END LOOP;
END IF;
END;
/
A few notes:
I'm assuming that you've set MAX_STRING_SIZE to EXTENDED. Otherwise, you'll have an issue with VARCHAR2 that big.
As I said, that is the simplest way to do this. If you're expecting a huge result set, you'll want to look into chunking it up. This Oracle blog post is very helpful in giving you multiple options for how to perform bulk processing. (Blog Post)
declare
vquery long;
cursor c1 is
select * from temp_name;
begin
for i in c1
loop
vquery :='INSERT INTO ot.temp_new(id)
select '''||i.id||''' from ot.customers';
dbms_output.put_line(i.id);
end loop;
end;
/
Output of select * from temp_name is :
ID
--------------------------------------------------------------------------------
customer_id
1 row selected.
I have customers table which has customer_id column.I want to insert all the customer_id into temp_new table but it is not being inserted. The PLSQL block executes successfully but the temp_new table is empty.
The output of dbms_output.put_line(i.id); is
customer_id
What is wrong there?
The main problem is that you generate a dynamic statement that you never execute; at some point you need to do:
execute immediate vquery;
But there are other problems. If you output the generated vquery string you'll see it contains:
INSERT INTO ot.temp_new(id)
select 'customer_id' from ot.customers
which means that for every row in customers you'll get one row in temp_new with ID set to the same fixed literal 'customer_id'. It's unlikely that's what you want; if customer_id is a column name from customers then it shouldn't be in single quotes.
As #mathguy suggested, long is not a sensible data type to use; you could use a CLOB but only really need a varchar2 here. So something more like this, where I've also switched to use an implicit cursor:
declare
l_stmt varchar2(4000);
begin
for i in (select id from temp_name)
loop
l_stmt := 'INSERT INTO temp_new(id) select '||i.id||' from customers';
dbms_output.put_line(i.id);
dbms_output.put_line(l_stmt);
execute immediate l_stmt;
end loop;
end;
/
db<>fiddle
The loop doesn't really make sense though; if your temp_name table had multiple rows with different column names, you'd try to insert the corresponding values from those columns in the customers table into multiple rows in temp_new, all in the same id column, as shown in this db<>fiddle.
I guess this is the starting point for something more complicated, but still seems a little odd.
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 situation:
I have a table named Table1. It has lots of columns, one of them is Column1. I don't know the other columns, they may even change sometimes.
There is a strongly typed ref cursor type which returns Table1%rowtype, named cur_Table1.
I have a stored procedure named SP1 which has an out parameter of type cur_Table1. I'm calling this SP1 stored procedure from another database that only sees this stored procedure, but not the table or the type itself.
How do I select only Column1 from the returned cursor?
I know I can fetch into a record or as many variables as the cursor has columns, but I only know of one column's existence so I can't declare the complete record or correct number of variables.
You can do this with DBMS_SQL, but it ain't pretty.
Table and sample data (COLUMN1 has the numbers 1 - 10):
create table table1(column1 number, column2 date, column3 varchar2(1000), column4 clob);
insert into table1
select level, sysdate, level, level from dual connect by level <= 10;
commit;
Package with a procedure that opens a ref cursor and selects everything:
create or replace package test_pkg is
type cur_Table1 is ref cursor return table1%rowtype;
procedure sp1(p_cursor in out cur_table1);
end;
/
create or replace package body test_pkg is
procedure sp1(p_cursor in out cur_table1) is
begin
open p_cursor for select column1, column2, column3, column4 from table1;
end;
end;
/
PL/SQL block that reads COLUMN1 data from the ref cursor:
--Basic steps are: call procedure, convert cursor, describe and find columns,
--then fetch rows and retrieve column values.
--
--Each possible data type for COLUMN1 needs to be added here.
--Currently only NUMBER is supported.
declare
v_cursor sys_refcursor;
v_cursor_number number;
v_columns number;
v_desc_tab dbms_sql.desc_tab;
v_position number;
v_typecode number;
v_number_value number;
begin
--Call procedure to open cursor
test_pkg.sp1(v_cursor);
--Convert cursor to DBMS_SQL cursor
v_cursor_number := dbms_sql.to_cursor_number(rc => v_cursor);
--Get information on the columns
dbms_sql.describe_columns(v_cursor_number, v_columns, v_desc_tab);
--Loop through all the columns, find COLUMN1 position and type
for i in 1 .. v_desc_tab.count loop
if v_desc_tab(i).col_name = 'COLUMN1' then
v_position := i;
v_typecode := v_desc_tab(i).col_type;
--Pick COLUMN1 to be selected.
if v_typecode = dbms_types.typecode_number then
dbms_sql.define_column(v_cursor_number, i, v_number_value);
--...repeat for every possible type.
end if;
end if;
end loop;
--Fetch all the rows, then get the relevant column value and print it
while dbms_sql.fetch_rows(v_cursor_number) > 0 loop
if v_typecode = dbms_types.typecode_number then
dbms_sql.column_value(v_cursor_number, v_position, v_number_value);
dbms_output.put_line('Value: '||v_number_value);
--...repeat for every possible type
end if;
end loop;
end;
/
Given the original question, jonearles's answer is still correct, so I'll leave it marked as such, but I ended up doing something completely different and much better.
The problem was/is that I have no control over SP1's database, I just have to call it from somewhere else as a 3rd party client. Now I managed to get permission to see not only SP, but also the type of the cursor. I still don't see the table but now there is a much cleaner solution:
In the other database I have been granted access to see this type now:
type cur_Table1 is ref cursor return Table1%rowtype;
So in my database I can do this now:
mycursor OtherDB.cur_Table1;
myrecord mycursor%rowtype;
...
OtherDB.SP1(mycursor);
fetch mycursor into myrecord;
dbms_output.put_line(myrecord.Column1);
See, I still don't need any access to the table, I see the cursor only. The key is that the magical %rowtype works for cursors as well, not just tables. It doesn't work on a sys_refcursor, but it does on a strongly typed one. Given this code, I don't have to care if anything changes on the other side, I don't have to define all the columns or records at all, I just specify the one column I'm interested in.
I really love this OOP attitude about Oracle.
Don't know if it's an option or not, but wouldn't a better solution be to create a function that returns the specific value you're looking for? That avoids the overhead of sending the extra data. Alternatively, you could define a cursor with a set of known fields in it that both parties know about.