PL/SQL:how to transform a string in an executable sql statment?

[Jeronimo]

Hi,
I have a problem concerning PL/SQL, and I want to describe it on a concrete example:
Let's suppose that you have a table called "Sqlstatement_Table". Here's the code for that table:
CREATE TABLE Sqlstatement_Table(
Statement VARCHAR2(200));

Let there be only one entry in the table: the string 'Select * FROM X_Table'.
OK, and now, I want to execute this statement. Therefore, I write the following code:

DECLARE
h_var VARCHAR2(200);
BEGIN
select Statement into h_var from Sqlstatement_Table;
??? EXECUTE IMMEDIATE h_var; ???
END;
/

The variable h_var contains now the string 'Select * FROM X_Table'. It doesn't work like this; the line between ??? is not correct. But how can I transform this string in an executable SQL statement? How can I make ORACLE execute this code?

-Thanks for your help!
Jeronimo

 

[MikeLacey]

Hi Jeronimo,

The code you posted, if you type it into sql/plus exactly as below, will run.

Sql/plus will see the final / and run the block.

DECLARE
h_var VARCHAR2(200);
BEGIN
Select Statement into h_var from Sqlstatement_Table;
END;
/

or if you save that text into a file called cmd.sql you could run it like this:

sqlplus user/pass @cmd


[sig]<p>Mike<br><a href=mailto:michael.j.lacey@ntlworld.com>michael.j.lacey@ntlworld.com</a><br><a href=

http://www.cargill.com/>

Cargill's Corporate Web Site</a><br> [/sig]

 

[yaffle]

This sort of construct may work for other forms of DML statement (e.g. inserts), but it won't work for selects. Select statements return a result set (the column values), but you haven't provided anywhere for your results to be put. [sig][/sig]

 

[yaffle]

Oops, typing too slow, you got in before me Mike.
I was assuming the problem was dynamically executing the statement stored in the table row ? [sig][/sig]

 

[Jeronimo]

Hi Mike, hi yaffle

thanks for your replies! Mike, I'm sorry, but it does not work. But let me describe the problem in more details: I have the following tables:

create table demo_table(
dummy VARCHAR2(200));

insert into demo_table values('Hello!');

create table sqlstatement_table(
statement VARCHAR2(200));

insert into Sqlstatement_Table values('SELECT * FROM demo_table')

Ok. Now, I want to execute the statement which is still a string. I use the following PL/SQL code from sqlplus and get an error:

SQL> DECLARE
2 h_var VARCHAR2(200);
3
4 BEGIN
5
6 select Statement into h_var from Sqlstatement_Table;
7 EXECUTE IMMEDIATE h_var;
8
9 END;
10 /

*
ERROR at line 3:
ORA-03113: end-of-file on communication channel

And now, nothing works anymore:

SQL> select * from user_catalog;
select * from user_catalog
*
ERROR at line 1:
ORA-01041: internal error. hostdef extension doesn't exist

Does anybody know what happened here? I have to restart sqlplus to continue.

Jeron

 

[MikeLacey]

prob a stupid question but:

what does &quot;EXECUTE IMMEDIATE h_var;&quot; do? [sig]<p>Mike<br><a href=mailto:michael.j.lacey@ntlworld.com>michael.j.lacey@ntlworld.com</a><br><a href=

http://www.cargill.com/>

Cargill's Corporate Web Site</a><br> [/sig]

 

[carp]

Mike -
EXECUTE IMMEDIATE is the 8i way of running a dynamic statement, as in:

EXECUTE IMMEDIATE 'CREATE TABLE x (y DATE)';

The error Jeron shows indicates to me that his session is getting terminated for some reason. And as Yaffle points out, the SELECT statement will run into problems because there is no place to return the results to.

Jeron - try your code using a DML or DDL statement and see if you get better results. [sig][/sig]

 

[Guest_imported]

Hi,

many thanks for your help! In fact, the &quot;execute immediate&quot;-statement deos not work with a select. The ony way of dealing with this problem is by using dynamic sql. The key is the DBMS_SQL package (see also

http://www.oracle.com/oramag/webcolumns/vallam.html).

I finally could solve this problem!

Jeron