I have a long DDL data migration script which has 15 transaction blocks. For each block, it takes data from one table and then inserts into another table.
But now I have come across a scenario in which the database does not have that table. In this case my script does not compile even.
What I actually want is to check and return early if the table does not exist. If it does, then only continue further execution.
But the script does not even compiles since it has statement which contains a table name which is non-existent in that particular database.
After some googling, I found that we can use those statements in EXECUTE IMMEDIATE block. I have tried this, but haven't been able to get it compiled.
Here is the block -
DECLARE
V_OBJECT_NAME1 VARCHAR2(50);
V_STRING VARCHAR2(1000);
V_CONTINUE Boolean;
BEGIN
V_CONTINUE := true;
SELECT TABLE_NAME INTO V_OBJECT_NAME1 FROM USER_TABLES WHERE TABLE_NAME = 'OOLD_SFWID_CHG_LOG_HEADER';
EXCEPTION WHEN NO_DATA_FOUND THEN
V_CONTINUE := false;
IF V_CONTINUE then
--scubbber code
V_STRING := 'DECLARE
CURSOR C1 IS
SELECT * FROM OOLD_SFWID_CHG_LOG_HEADER;
BEGIN
OPEN C1;
CLOSE C1;
END;';
EXECUTE IMMEDIATE V_STRING
END IF;
END;
Please suggest how can we write it..
Related
I have a code in oracle pl sql, want to really want to understand how much context switching is there
If x=0 then
curserx= select a from mytable1;
Else
curserx=select a from mytable1 where id=:x;
End;
Loop
Fetch on cursorx
Select c from mytable2 where a=curserx.a;
End loop;
This is just a sample code so please pardon any text casing and logic error.
I converted your pseudo code into PL/SQL and include comments indicating where I believe you will have a context switch from the PL/SQL engine to the SQL engine.
Note that if you are querying a non-trivial number of rows, you could use FETCH BULK COLLECT INTO and retrieve multiple rows with each fetch, greatly reducing context switches.
DECLARE
l_x_value INTEGER;
l_cursor SYS_REFCURSOR;
l_fetched mytble1.a%TYPE;
BEGIN
/* context switch to open */
IF x = 0
THEN
OPEN l_cursor FOR SELECT a FROM mytable1;
ELSE
OPEN l_cursor FOR
SELECT a
FROM mytable1
WHERE id = l_x_value;
END IF;
LOOP
/* context switch per fetch */
FETCH l_cursor INTO l_fetched;
EXIT WHEN l_cursor%NOTFOUND;
/* context switch for implicit cursor */
SELECT c
INTO l_fetched
FROM mytable2
WHERE a = curserx.a;
END LOOP;
/* context switch to close */
CLOSE l_cursor;
END;
But that's not all! Remember that the context switch works both ways: SQL -> PL/SQL and PL/SQL -> SQL. You can reduce the overhead of going from SQL to PL/SQL by declaring your function with the UDF pragma (12c+) or defining it with the WITH FUNCTION clause (also 12c+). There is still a context switch but some of the work is done at compile time instead of run time.
So in the code below, for each invocation of the function from within the SELECT, there is a switch.
CREATE OR REPLACE FUNCTION full_name (first_in IN VARCHAR2,
last_in IN VARCHAR2)
RETURN VARCHAR2
IS
BEGIN
RETURN first_in || ' ' || last_in;
END;
/
DECLARE
l_name VARCHAR2 (32767);
BEGIN
SELECT full_name (first_name, last_name) INTO l_name
FROM employees
WHERE employee_id = 100;
DBMS_OUTPUT.PUT_LINE (l_name);
END;
/
Finally a cautionary note: you should do everything you can to avoid executing SQL inside a function that is then called from SQL. The standard read consistency model that works for your SQL statement will not be "carried in" to the function's SQL. In other words, if you "outer" SELECT starts running at 10:00 and runs for an hour, and at 10:05, someone deletes rows from a table that is used in both the outer query and the query in the function (and commits), those two queries will be working with different states of those tables.
I am new in Oracle,
In SQL Server I can easily execute a stored procedure inside storedprocedure
even using a cursor.
now I can't figure it out in Oracle here is my code below.
CREATE OR REPLACE PROCEDURE ZSP_INSMASTERDATASTM
AS
l_total INTEGER := 10000;
CURSOR c1
IS
SELECT DISTINCT PRODFROMTO FROM DJ_P9945LINKS;
l_PRODFROMTO c1%ROWTYPE;
BEGIN
OPEN c1;
LOOP
FETCH c1 INTO l_PRODFROMTO;
EXIT WHEN c1%NOTFOUND;
EXECUTE ZSP_GETMASTERDATASTM (l_PRODFROMTO);
EXIT WHEN l_total <= 0;
END LOOP;
CLOSE c1;
END ZSP_INSMASTERDATASTM;
i got error on execute ZSP_GETMASTERDATASTM (l_PRODFROMTO);
Just remove EXECUTE. However, note that your loop will NEVER exit because L_TOTAL is never going to be less than zero - you should fix that.
Otherwise, consider using cursor FOR loop as it is simpler to maintain - you don't have to declare a cursor variable, open cursor, fetch, take care about exiting the loop, close the cursor. Have a look at this example:
CREATE OR REPLACE PROCEDURE zsp_insmasterdatastm
AS
BEGIN
FOR cur_r IN (SELECT DISTINCT prodfromto FROM dj_p9945links)
LOOP
zsp_getmasterdatastm (cur_r.prodfromto);
END LOOP;
END;
Quite simpler, isn't it?
I created a procedure to calculate the hashcode of a record (complete line of a table) and then update a column with the calculated hashcode number.
Here's my code at this point (which is based on some info I manage to gather from Google):
CREATE OR REPLACE PROCEDURE calcHashCode (inputTableString IN varchar2) IS
c_data varchar2(3000); --QUERY
c_cursor sys_refcursor; --CURSOR
c_record inputTableString%rowtype; -- Problem is here
BEGIN
c_data := 'SELECT * FROM ' || inputTableString;
OPEN c_cursor for c_data;
LOOP
FETCH c_cursor INTO c_record;
EXIT WHEN c_cursor%notfound;
-- will do stuff here with the records
dbms_output.put_line('stuff');
END LOOP;
CLOSE c_cursor;
END;
/
SHOW ERRORS
4/13 PLS-00310: with %ROWTYPE attribute, 'INPUTTABELA' must name a table, cursor or cursor-variable
4/13 PL/SQL: Item ignored
11/25 PLS-00320: the declaration of the type of this expression is incomplete or malformed
11/5 PL/SQL: SQL Statement ignored
So, my idea (for the final stage of the procedure) is to iterate through out the records, build a string with and then calculate the hashcode. After that, I'll run the update instruction.
The thing is at this point using a varchar as an argument and I'm not being able to iterate through the table in order to get my concatenate records.
dynamic cursors are the ugliest...
the problem is with that section:
c_data varchar2(3000); --QUERY
c_cursor sys_refcursor; --CURSOR
c_record inputTableString%rowtype;
i used something like this:
TYPE t_data IS REF CURSOR;
cr_data t_data;
cr_data_rec inputTableString%ROWTYPE; --that table need to be exists in compile time
the rest are good i think
Have you considered pushing the whole declaration and loop into an anonymous block that will then get executed by EXECUTE IMMEDIATE? You can then simplify your looping construct to a simple FOR loop too.
I'm away from my database at the moment, so excuse any syntax glitches, but something like
CREATE OR REPLACE PROCEDURE calcHashCode (inputTableString IN varchar2) IS
c_data varchar2(30000); --QUERY
BEGIN
c_data := '
BEGIN
FOR aRec IN
(SELECT * FROM ' || inputTableString ||' )
LOOP
--do your stuff
END LOOP;
END';
execute immediate c_Data;
END;
/
It may not be pretty, and your "Stuff" may not easily be able to be fit into this construct, but it IS feasible
You can do all this kind of stuff with PL/SQL package DBMS_SQL, however it is definitely not for beginners and you should start with something easier.
Examples for DBMS_SQL
I have this code:
BEGIN
FOR
U1 IN (SELECT * FROM SOME_USER.SOME_TABLE)
LOOP
BEGIN
-- do something;
END;
END LOOP;
END;
My problem is that sometimes SOME_USER.SOMETABLE do not exists but I want the rest of the script to be run. I know that checking if the table exists before running the code (in a IF ... THEN block) will not work because SELECT * FROM SOME_USER.SOME_TABLE is evaluated at compile time.
So another avenue is to run the SELECT with EXECUTE IMMEDIATE. This way it will be evaluated at run time and I would be able to catch the exception. Unfortunately I can't find a way to use EXECUTE IMMEDIATE with my U1 IN loop. How I should achieve this?
I'm on Oracle 11g and the SQL script is run from a batch script on Windows.
You can use the 'OPEN FOR' syntax:
DECLARE
CUR SYS_REFCURSOR;
<variables or record type> -- declare as appropriate
BEGIN
OPEN CUR FOR 'SELECT * FROM SOME_USER.SOME_TABLE';
LOOP
FETCH CUR INTO <variables or record type>;
EXIT WHEN CUR%NOTFOUND;
-- do something with variables or record
END LOOP;
CLOSE CUR;
END;
/
You need to fetch each row into variables or a record type, you can't use %ROWTYPE as the table still won't exist; and you can change to do bulk fetches if that's appropriate for your data volumes.
If you run that you'll still get ORA-00942, but if this is in a stored program you won't get it until run time, and you can now add an IF block to check for the table's existence before the OPEN.
Having a data model where objects may or may not exist at run-time seems rather fishy though...
Proposed solution with cursor is fine, I would add an exception handling for this particular exception : Table or view does not exist ORA-00942.
DECLARE
e_missing_t EXCEPTION;
pragma exception_init (e_missing_t,-942);
something number; --some variable you need to fetch to
CUR SYS_REFCURSOR;
BEGIN
OPEN CUR FOR 'SELECT * FROM SOME_USER.SOME_TABLE';
LOOP
FETCH CUR INTO something;
EXIT WHEN CUR%NOTFOUND;
-- do something with variables or record
END LOOP;
CLOSE CUR;
EXCEPTION
WHEN e_missing_t THEN
dbms_output.put_line('some_table is missing');
END;
/
You could possibly use a workaround -
Create a nested table type and store the results of the SELECT in it. Use that type to loop through values.
So,
SELECT data_obj(COL1, COL2) bulk collect into data_tbl_typ from data_table;
This part can go in the dynamic sql. (Remember to use bind variables)
And then just loop through this nested table type in your procedure.
Use the DBMS_SQL package to run the query.
Follow the examples in this Oracle documentation:
http://docs.oracle.com/cd/B19306_01/appdev.102/b14258/d_sql.htm#sthref6147
pl/sql has the exception clause for that. OTHERS catches pretty much everything. You can deal with the exception in the function, or print a message and pass it back to the main. Break your function up into smaller functions and have each one catch it's own exception.
BEGIN
FOR
U1 IN (SELECT * FROM SOME_USER.SOME_TABLE)
LOOP
BEGIN
-- do something;
END;
END LOOP;
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE ('Oh well. The table isn't there.');
--RAISE;
END;
I've a query that creates a SQL Statement as a field. I want to execute this statement and return the recordset in SSRS report.
select 'select '||FILE_ID||' FILE_ID,'||
ltrim(sys_connect_by_path('REC_FLD_'||FIELD_NUMBER||' "'||FIELD_NAME||'"',','),',')||
' from RESPONSE_DETAILS where FILE_ID=' ||FILE_ID||';'
from (select t.*,count(*) over (partition by FILE_ID) cnt from RESPONSE_METADATA t)
where cnt=FIELD_NUMBER start with FIELD_NUMBER=1
connect by prior FILE_ID=FILE_ID and prior FIELD_NUMBER=FIELD_NUMBER-1
This generates a SQL stetment - however I want this SQL to be executed.
This is an extension of this question.
I've tried to use execute immediate , cursors, dbms_sql but it does not produce output. Using it on toad. All it says is "PL/SQL procedure successfully completed"
Using the following
Declare
sql_stmt VARCHAR2(3000);
l_cursor SYS_REFCURSOR;
TYPE RefCurTyp IS REF CURSOR;
v_cursor RefCurTyp;
CURSOR c1 is
select 'select '||FILE_ID||' FILE_ID,'||
ltrim(sys_connect_by_path('REC_FLD_'||FIELD_NUMBER||' "'||FIELD_NAME||'"',','),',')||
' from RESPONSE_DETAILS where FILE_ID=' ||FILE_ID||';'
from (select t.*,count(*) over (partition by FILE_ID) cnt from RESPONSE_METADATA t)
where cnt=FIELD_NUMBER start with FIELD_NUMBER=1
connect by prior FILE_ID=FILE_ID and prior FIELD_NUMBER=FIELD_NUMBER-1;
BEGIN
open c1;
FETCH C1 into sql_stmt ;
dbms_output.put_line(sql_stmt);
close c1;
EXECUTE IMMEDIATE sql_stmt;
open v_cursor for sql_stmt;
return l_cursor;
close l_cursor ;
END;
An anonymous PL/SQL block cannot return any data to the caller. If you want to return a SYS_REFCURSOR to the calling application, you would need to create a function (or a procedure). For example
CREATE OR REPLACE FUNCTION get_results
RETURN sys_refcursor
IS
l_sql_stmt VARCHAR2(3000);
l_cursor SYS_REFCURSOR;
BEGIN
select 'select '||FILE_ID||' FILE_ID,'||
ltrim(sys_connect_by_path('REC_FLD_'||FIELD_NUMBER||' "'||FIELD_NAME||'"',','),',')||
' from RESPONSE_DETAILS where FILE_ID = ' ||FILE_ID||';'
into l_sql_stmt
from (select t.*,count(*) over (partition by FILE_ID) cnt from RESPONSE_METADATA t)
where cnt=FIELD_NUMBER
start with FIELD_NUMBER=1
connect by prior FILE_ID=FILE_ID
and prior FIELD_NUMBER=FIELD_NUMBER-1;
dbms_output.put_line(l_sql_stmt);
open l_cursor for sql_stmt;
return l_cursor;
END;
I am assuming from your code that you expect your SELECT statement to return a single SQL statement-- your code is fetching only one row from a query that potentially returns multiple SQL statements. I'm assuming that you only fetch one because you only expect the SELECT statement to return one row. Otherwise, since your query lacks an ORDER BY, you are executing arbitrarily one of N SQL statements that your code is generating.
If you are regularly going to be calling this method, you would almost certainly want to use bind variables in your dynamic SQL statement for the file_id rather than generating non-sharable SQL statements. I haven't made that change here.
There is another StackOverflow thread on calling a stored function returning a sys_refcursor from SSRS.