I have a requirement where I have to select name of DB link (there are many DB links) from a table into bind variable and then fetch data from a table which is available in all DB links however data is different depending on DB link used. I am not getting a solution to use bind variables value as DB link.
This is my code:
select statement for fetching DB link into bind variable
SELECT DB_LINK into :v_db_link from reagions_db_links;
Then I have to use it for fetching data from table
SELECT reagion_id, region_name from Table_details#:v_db_link
I have tried to concatenate like below however its not working
SELECT reagion_id, region_name from Table_details#||:v_db_link
Please suggest me a solution, since I could have many DB links depending upon region selected by USER I am putting it into bind variable and then want to use it for fetching data from a table.
Substitution variables can be used for that. here is a quick example of how it can be done:
(Sql*plus environment).
-- set-up table that stores db_links
SQL> create table db_links(
2 dblink_name varchar2(31)
3 );
Table created.
--add a test dblink
SQL> insert into db_links(dblink_name) values ('TEST_DB_LINK');
1 row created.
SQL> commit;
Commit complete.
-- defining of a substitution variable dblink
SQL> column dblink_name new_value dblink noprint;
-- the value of the dblink_name column will be placed into the dblink
-- substitution variable declared previously
SQL> select dblink_name from db_links;
-- now we query a table using db link name stored
-- in the dblink substitution variable
-- prefacing it with ampersand.
SQL> select count(*) from dbusers#&dblink;
old 1: select count(*) from dbusers#&dblink
new 1: select count(*) from dbusers#TEST_DB_LINK
COUNT(*)
----------
351
SQL> spool off;
Related
I am trying to create a DML file that contains all the inserts to a database using only a script and asking only for the owner name, I found some documentation about the creation of files in Oracle and some other about how to get the insert statements.
This is the query that gets the inserts
SELECT /*insert*/ * FROM ALL_TAB_COLUMNS WHERE OWNER = 'OwnerName';
And this is what I`m trying to do in order to create the file with the selected rows from the query
DECLARE
F1 UTL_FILE.FILE_TYPE;
CURSOR C_TABLAS IS
SELECT /*insert*/ * FROM ALL_TAB_COLUMNS WHERE OWNER = 'BETA';
V_INSERT VARCHAR2(32767);
BEGIN
OPEN C_TABLAS;
LOOP
FETCH C_TABLAS INTO V_INSERT;
EXIT WHEN C_TABLAS%NOTFOUND;
F1 := UTL_FILE.FOPEN('D:\Desktop\CENFOTEC\4 Cuatrimestre\Programación de Bases de Datos\Proyecto\FileTests','TestUno.dml','W');
UTL_FILE.PUT_LINE(F1, V_INSERT);
UTL_FILE.FCLOSE (F1);
END LOOP;
CLOSE C_TABLAS;
END;
I'm having trouble with the fetch, I'm getting this error: wrong number of values in the INTO list of a FETCH statement
I know that it is a basic one, but I can't figure out how many columns I am getting from the query above
Although I'm trying this way i wouldn't mind changing it, I need to create a DML file of all the inserts needed to replicate the database of the given user. Thanks a lot
In SQL Developer, when you use:
SELECT /*insert*/ * FROM ALL_TAB_COLUMNS WHERE OWNER = 'OwnerName';
Then the /*insert*/ hint is processed by SQL Developer on the client-side and converts the returned result set into DML statements.
To quote #ThatJeffSmith in his answer where he gave the above solution:
here is a SQL Developer-specific solution
That behaviour is specific to the SQL Developer client application.
In the Oracle database, when you use:
SELECT /*insert*/ * FROM ALL_TAB_COLUMNS WHERE OWNER = 'OwnerName';
Then /*insert*/ is an inline comment and it is IGNORED and has zero effect on the output of the query.
Therefore, when you do:
DECLARE
F1 UTL_FILE.FILE_TYPE;
CURSOR C_TABLAS IS
SELECT /*insert*/ * FROM ALL_TAB_COLUMNS WHERE OWNER = 'BETA';
V_INSERT VARCHAR2(32767);
BEGIN
OPEN C_TABLAS;
LOOP
FETCH C_TABLAS INTO V_INSERT;
EXIT WHEN C_TABLAS%NOTFOUND;
F1 := UTL_FILE.FOPEN('D:\Desktop\CENFOTEC\4 Cuatrimestre\Programación de Bases de Datos\Proyecto\FileTests','TestUno.dml','W');
UTL_FILE.PUT_LINE(F1, V_INSERT);
UTL_FILE.FCLOSE (F1);
END LOOP;
CLOSE C_TABLAS;
END;
/
The PL/SQL anonymous block will be processed by the database's PL/SQL engine on the server-side and it will context-switch and pass the cursor's SQL to the database's SQL engine where it will be run and the /*insert*/ comment is ignored and it will return all the columns.
I can't figure out how many columns I am getting from the query above.
One column for every column in the ALL_TABS_COLUMNS table. You can use:
SELECT * FROM all_tabs_columns FETCH FIRST ROW ONLY
And then count the columns. I made it 37 columns (but might have miscounted).
However
Trying to generate INSERT statements that correspond to all the rows in the ALL_TAB_COLUMNS table so that you can recreate the database is WRONG. You need to generate the DDL statements for each table and not generate DML statements to try to modify a data dictionary table (which, likely as not, if you try to modify data dictionary tables will leave your database in an unusable state).
If you want to recreate the database then use the answers in this question or backup the database and then restore it to the new database.
I have an Oracle database with a couple of public dblinks for various customers. All linked databases for all customers are identical. Also I have a schema on my host machine only, where I stored DB views with some data retrieval logic.
Currently, if I want to retrieve the same data from various customers, I have to create separate almost identical views for every client:
CREATE VIEW my_view_for_cliet1 AS
SELECT *
FROM table1#dblink1;
CREATE VIEW my_view_for_cliet2 AS
SELECT *
FROM table1#dblink2
Is it possible to set default dblink for session (or something similar) and have only one DB view without explicit dblink, for example:
CREATE VIEW my_view AS
SELECT *
FROM table1;
-- below I want to retrieve data from 3rd client
ALTER SESSION SET DEFAULT DBLINK dblink3;
SELECT * FROM my_view;
P.S. I have only SELECT rights on linked machines so I can't create any views or other objects.
No, that is not possible. Every reference to a dblink must be explicit.
Note that each of the other solutions presented (so far) can give the appearance of what you're asking, but still require explicit dblink references in all of the actual views and thus the same DDL changes for every new link and/or client user. There's no way to avoid creating those individual views or explicit references at some level (which is what I believe you were asking), even if you hide them somewhat from the user.
I'd suggest using synonyms, and set up a procedure to change them all at once, e.g.
create or replace procedure SET_DBLINK ( target_link IN VARCHAR2 ) is
begin
execute immediate 'create or replace synonym TABLE1 for TABLE1#' || target_link;
execute immediate 'create or replace synonym TABLE2 for TABLE2#' || target_link;
-- ...etc...
end;
/
That way you could do:
exec SET_DBLINK('dblink3');
select * from table1;
You'd probably want to add validation and exception handling to the procedure, but I left it simple for readability.
For example, user manager
CREATE OR REPLACE VIEW manager.example1 (
column1,
column2
)
AS
select 1, user from dual#dblink1
where 'SCOTT'=user
union all
select 2, user from dual#dblink2
where 'MANAGER'=user
union all
select 3, user from dual#dblink3
where 'HR'=user;
grant select on example1 to scott;
grant select on example1 to hr;
select * from example1;
==>
COLUMN1 COLUMN2
-------------------------------------------- ------------------------------------
2 MANAGER
user scott
create synonym example1 for manager.example1;
select * from example1;
==>
COLUMN1 COLUMN2
-------------------------------------------- ------------------------------------
1 SCOTT
user hr
create synonym example1 for manager.example1;
select * from example1;
==>
COLUMN1 COLUMN2
-------------------------------------------- ------------------------------------
3 HR
The only thing I found is renaming one column at a time:
ALTER TABLE table_name
RENAME COLUMN old_name TO new_name;
I read Oracle documentations, and couldn't get the answer for many columns at a time .
Ref: https://docs.oracle.com/javadb/10.6.2.1/ref/rrefsqljrenamecolumnstatement.html
It is not possible to rename multiple table columns in a single command, as of Oracle 18c.
The Oracle 18c SQL Language Reference includes the below diagram to illustrate how the RENAME_COLUMN_CLAUSE of the ALTER TABLE command works. Unfortunately, almost every column property can be modified in groups, except for renaming.
You can use user_tab_columns dictionary view as a data source within a cursor for a loop statement
declare
v_table_name varchar2(40):='mytable';
begin
for c in ( select from user_tab_columns where table_name = upper(v_table_name) )
loop
execute immediate ('ALTER TABLE '||c.table_name||' RENAME COLUMN '||c.column_name
||' TO new_'||c.column_name);
end loop;
end;
Using this command, I am able to create a table from another schema, but it does not include triggers. Is it possible to create a table from another schema, including triggers?
create table B.tablename unrecoverable as select * from A.tablename where 1 = 0;
First option is to run CREATE script for those objects, if you have a code repository. I suppose you don't.
If you use any GUI tool, things are getting simpler as they contain the SCRIPT tab that enables you to copy code from source and paste it into target user.
If you're on SQLPlus, it means that you should, actually, know what you're supposed to do. Here's a short demo.
SQL> connect hr/hr#xe
Connected.
SQL> create table detail (id number);
Table created.
SQL> create or replace trigger trg_det
2 before insert on detail
3 for each row
4 begin
5 :new.id := 1000;
6 end;
7 /
Trigger created.
SQL>
SQL> -- you'll have to grant privileges on table to another user
SQL> grant all on detail to scott;
Grant succeeded.
Connect as SCOTT and check what we've got:
SQL> connect scott/tiger#xe
Connected.
SQL> -- now, query ALL_SOURCE and you'll get trigger code
SQL> set pagesize 0
SQL> col text format a50
SQL> select text from all_source where name = 'TRG_DET' order by line;
trigger trg_det
before insert on detail
for each row
begin
:new.id := 1000;
end;
6 rows selected.
SQL>
Yet another option is to export & import table, which will get the trigger as well (I've removed parts that aren't relevant, as Oracle database version):
C:\>exp hr/hr#xe tables=detail file=detail.dmp
About to export specified tables via Conventional Path ...
. . exporting table DETAIL 0 rows exported
Export terminated successfully without warnings.
C:\>imp scott/tiger#xe file=detail.dmp full=y
. importing HR's objects into SCOTT
. importing HR's objects into SCOTT
. . importing table "DETAIL" 0 rows imported
Import terminated successfully without warnings.
C:\>
Check what's imported (should be both table and trigger):
SQL> desc detail
Name Null? Type
----------------------------------------- -------- ---------------
ID NUMBER
SQL> select * From detail;
no rows selected
SQL> insert into detail (id) values (-1);
1 row created.
SQL> select * From detail;
ID
----------
1000
SQL>
Cool; even the trigger works.
There might be some other options, but these 4 should be enough to get you started.
I have a table TABLE_X and it has multiple columns beginning with M_ characters which needs to be dropped. I decided to use the following PLSQL code to drop almost 100 columns beginning with M_ characters. Is it a good employment of dynamic sql and cursors? Can it be better? I didn't know more simple way since ALTER TABLE ... DROP COLUMN doesn't allow subquery to specify multiple column names.
declare
rcur sys_refcursor;
cn user_tab_cols.column_name%type;
begin
open rcur for select column_name from user_tab_cols where table_name='TABLE_X' and column_name LIKE 'M_%';
loop
fetch rcur into cn;
exit when rcur%NOTFOUND;
execute immediate 'alter table TABLE_X drop column '||cn;--works great
execute immediate 'alter table TABLE_X drop column :col'using cn;--error
end loop;
close rcur;
end;
Also. Why is it impossible to use 'using cn'?
This is a reasonable use of dynamic SQL. I would seriously question an underlying data model that has hundreds of columns in a single table that start with the same prefix and all need to be dropped. That implies to me that the data model itself is likely to be highly problematic.
Even using dynamic SQL, you cannot use bind variables for column names, table names, schema names, etc. Oracle needs to know at parse time what objects and columns are involved in a SQL statement. Since bind variables are supplied after the parse phase, however, you cannot specify a bind variable that changes what objects and/or columns a SQL statement is affecting.
The syntax for dropping multiple columns in a single alter statement is this:
SQL> desc t42
Name Null? Type
----------------------------------------- -------- ----------------------
COL1 NUMBER
COL2 DATE
COL3 VARCHAR2(30)
COL4 NUMBER
SQL> alter table t42 drop (col2, col3)
2 /
Table altered.
SQL> desc t42
Name Null? Type
----------------------------------------- -------- ----------------------
COL1 NUMBER
COL4 NUMBER
SQL>
So, if you really need to optimize the operation, you'll need to build up the statement incrementally - or use a string aggregation technique.
However, I would question whether you ought to be running a statement like this often enough to need to optimize it.