When dealing with an oracle table containing row objects I would expect that each row is an object and I can invoke functions on it or pass it to functions in any context.
As an example if I declare the following:
create type scd_type as object
(
valid_from date,
valid_to date,
member function get_new_valid_to return date
);
create type scd_type_table as table of scd_type;
create table scd_table of scd_type;
create procedure scd_proc (in_table in scd_type_table)
as
begin
... do stuff ...
end;
/
And now I try to call my proc with the table
begin
scd_proc (scd_table);
end;
/
I get an error. Even reading the rows into a nested table is not straight forward. I would expect it to work like this:
declare
temp_table scd_type_table;
begin
select * bulk collect into temp_table from scd_table;
... do stuff ...
end;
/
but instead I have to call the constructor for every line.
And last I cannot invoke functions in a merge statement even though it works in an update statement. Example:
update scd_table st
set st.valid_to = st.get_new_valid_to(); <--- Works.
merge into scd_table st
using (select sysdate as dateCol from dual) M
on (st.valid_from = M.dateCol)
when matched then update set st.valid_to = st.get_new_valid_to(); <--- Does not work.
So I guess there are three sub-questions here:
1) What is the easiest way to pass a table of row objects into a procedure expecting a nested table of the same type?
2) What is the easiest way to convert a table of row objects into a nested table of the same type?
3) Why can't I invoke functions on an object as part of a merge statement (but in an update statement)?
which all come down to the question of "How to extract objects from a table of row objects?".
I can't help but think you need to re-read the documentation on PL/SQL types.
You were close with the bulk collect code. Minor change given below:
declare
plsql_table scd_type_table;
begin
select VALUE(t) bulk collect into plsql_table from scd_table t;
-- do stuff
end;
/
I will admit, I have no idea why the merge fails but the update works.
Related
I have to write a stored procedure that starts copying the data from a table 'company' into a staging table 'company_stg' if no records for that date are present in it.
I have the following code :
CREATE OR REPLACE
PACKAGE BODY PKG_TEST AS
PROCEDURE SP_BILLING AS
BEGIN
EXECUTE IMMEDIATE 'SELECT * FROM COMPANY INTO COMPANY_STG
WHERE NOT EXISTS (SELECT * FROM COMPANY_STG WHERE AS_OF_DATE = "2023-02-08")';
END;
END PKG_TEST;
I AM GETTING THE ERROR "SQL COMMAND NOT PROPERLY ENDED"
company * company_stg have as_of_date as a column. rest all are same.
please help me with this
I have also tried
if not exists (SELECT * FROM COMPANY_STG WHERE AS_OF_DATE = "2023-02-08")
then
select from company into company_stg
So many things look bad in that piece of code...
First, why use dynamic SQL execute immediate? It's best to avoid dynamic SQL as much as possible because it leads to runtime errors and requires pretty much instrumentation so that it may be debugged. Generally you use dynamic SQL when you do not know beforehand the name of a table it will operate on, which is not the case for you. You definitely know you have to work with tables COMPANY and COMPANY_STG. Is it not so?
Then, it doesn't look like you have read the manual to see an insert select.
When you insert into a table, it's best to give the list of columns into which you actually insert data. If one alters that table and adds one or more than one column, the insert which does not have the list of columns will crash.
Thus, to insert into COMPANY_STG data from COMPANY, the SQL should look like below:
insert into company_stg(
... ---- here should be the list of columns you insert data into
)
select
... --- here should the source columns you are willing to insert
from company c
where not exists (
select 1
from company_stg cs
where cs.as_of_date= --- what is the condition??? I did not understand
)
;
You have not given the structures for those tables, so that I can't give you the columns to select and to insert into. Nor did I really understand what the condition for inserting data should be.
SELECT does not perform a copy and SELECT * FROM COMPANY INTO COMPANY_STG is not valid syntax. You want to use an INSERT statement to do that (and check if there is any row first):
CREATE OR REPLACE PACKAGE BODY PKG_TEST AS
PROCEDURE SP_BILLING
AS
BEGIN
DECLARE
v_staged_count NUMBER;
BEGIN
SELECT 1
INTO v_staged_count
FROM COMPANY_STG
WHERE AS_OF_DATE = DATE '2023-02-08'
FETCH FIRST ROW ONLY; -- We don't care how many rows so stop after finding
-- the first one.
-- Stop as rows have been found.
RETURN;
EXCEPTION
WHEN NO_DATA_FOUND THEN
-- Continue
NULL;
END;
INSERT INTO company_stg
SELECT *
FROM COMPANY;
END;
END PKG_TEST;
/
fiddle
Is there a way to write sql for Oracle, MS SQL:
Select * from table where id in(:arr)
Select * from table where id in(#arr)
With one param in sql 'arr' to represent an array of items?
I found examples that explode arr to #arr0,.., #arrn and feed array as n+1 separate parameters, not array, like this
Select * from table where id in(:arr0, :arr1, :arr2)
Select * from table where id in(#arr0, #arr1, #arr2)
Not what i want.
These will cause change in sql query and this creates new execution plans based on number of parameter.
I ask for .net, c# and Oracle and MS SQL.
Thanks for constructive ideas!
/ip/
I believe Table Value Parameter is good option for this case. Have a look at a sample code below in SQL Server.
-- Your table
CREATE TABLE SampleTable
(
ID INT
)
INSERT INTO SampleTable VALUES
(1010),
(2010),
(3010),
(4010),
(5010),
(6010),
(7010),
(8030)
GO
-- Create a TABLE type in SQL database which you can fill from front-end code
CREATE TYPE ParameterTableType AS TABLE
(
ParameterID INT
--, some other columns
)
GO
-- Create a stored proc using table type defined above
CREATE PROCEDURE ParameterArrayProcedure
(
#ParameterTable AS ParameterTableType READONLY
)
AS
BEGIN
SELECT
S.*
FROM SampleTable S
INNER JOIN #ParameterTable P ON S.ID = P.ParameterID
END
GO
-- Populated table type variable
DECLARE #ParameterTable AS ParameterTableType
INSERT INTO #ParameterTable (ParameterID) VALUES (1010), (4010), (7010)
EXECUTE ParameterArrayProcedure #ParameterTable
DROP PROCEDURE ParameterArrayProcedure
DROP TYPE ParameterTableType
DROP TABLE SampleTable
GO
Apart from Table Value Parameter, you can also use Json or XML values as SQL parameter but yes, it will definitely change your execution plan accordingly.
In addition to a Table Valued Parameter as Steve mentioned, there are a couple of other techniques available. For example you can parse a delimited string
Example
Declare #arr varchar(50) = '10,20,35'
Select A.*
From YourTable A
Join string_split(#arr,',') B on A.ID=value
Or even
Select A.*
From YourTable A
Where ID in ( select value from string_split(#arr,',') )
Oracle
In other languages (i.e. Java) you can pass an SQL collection as a bind parameter and directly use it in an SQL statement.
However, C# does not support passing SQL collections and only supports passing OracleCollectionType.PLSQLAssociativeArray (documentation link) which is a PL/SQL only data-type and cannot be used (directly) in SQL statements.
To pass an array, you would need to pass a PLSQLAssociativeArray to a PLSQL stored procedure and use that to convert it to an SQL collection that you can use in an SQL statement. An example of a procedure to convert from a PL/SQL associative array to an SQL collection is:
CREATE TYPE IntList AS TABLE OF INTEGER
/
CREATE PACKAGE tools IS
TYPE IntMap IS TABLE OF INTEGER INDEX BY BINARY_INTEGER;
FUNCTION IntMapToList(
i_map IntMap
) RETURN IntList;
END;
/
CREATE PACKAGE BODY tools IS
FUNCTION IntMapToList(
i_map IntMap
) RETURN IntList
IS
o_list IntList := IntList();
i BINARY_INTEGER;
BEGIN
IF i_map IS NOT NULL THEN
i := o_list.FIRST;
WHILE i IS NOT NULL LOOP
o_list.EXTEND;
o_list( o_list.COUNT ) := i_map( i );
i := i_map.NEXT( i );
END LOOP;
END IF;
RETURN o_list;
END;
END;
/
I discovered a mysterious table named num in my database which has one column named count. I had no idea how it got there, then I realized it might be caused by a misbehaving trigger.
I have a trigger function:
DECLARE num integer := 0;
BEGIN
IF ... THEN
SELECT COUNT(*) INTO num FROM ...
END IF;
IF num > 1 THEN
DELETE FROM ...
END IF;
RETURN NEW;
END;
As you can see my purpose is to count the rows returned by a query and perform some operation if it is greater than one.
Can this faulty code be responsible for the unwanted table created? If so, how to fix this?
SELECT ... INTO foo in PL/pgSQL stores the result of the SELECT in a PL/pgSQL variable foo. Whereas SELECT ... INTO foo run as an ordinary SQL statement creates a table foo to store the result.
This is what caused the confusion, the table was created when I was testing the SQL statements from the trigger function manually against the DB.
All i want is to select all rows from a table and once it is selected and displayed, the data residing in table must get completely deleted. The main concern is that this must be done using sql only and not plsql. Is there a way we can do this inside a package and call that package in a select statement? Please enlighten me here.
Dummy Table is as follows:
ID NAME SALARY DEPT
==================================
1 Sam 50000 HR
2 Max 45000 SALES
3 Lex 51000 HR
4 Nate 66000 DEV
Any help would be greatly appreciated.
select * from Table_Name;
Delete from Table_Name
To select the data from a SQL query try using a pipelined function.
The function can define a cursor for the data you want (or all the data in the table), loop through the cursor piping each row as it goes.
When the cursor loop ends, i.e. all data has been consumed by your query, the function can perform a TRUNCATE table.
To select from the function use the following syntax;
SELECT *
FROM TABLE(my_function)
See the following Oracle documentation for information pipelined functions - https://docs.oracle.com/cd/B28359_01/appdev.111/b28425/pipe_paral_tbl.htm
This cannot be done inside a package, because " this must be done using sql only and not plsql". A package is PL/SQL.
However it is very simple. You want two things: select the table data and delete it. Two things, two commands.
select * from mytable;
truncate mytable;
(You could replace truncate mytable; with delete from mytable;, but this is slower and needs to be followed by commit; to confirm the deletion and end the transaction.)
Without pl/sql it's not possible.
Using pl/sql you can create a function which will populate a row, and then delete
Here is example :
drop table tempdate;
create table tempdate as
select '1' id from dual
UNION
select '2' id from dual
CREATE TYPE t_tf_row AS OBJECT (
id NUMBER
);
CREATE TYPE t_tf_tab IS TABLE OF t_tf_row;
CREATE OR REPLACE FUNCTION get_tab_tf RETURN t_tf_tab PIPELINED AS
PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
FOR rec in (select * from tempdate) LOOP
PIPE ROW(t_tf_row(rec.id));
END LOOP;
delete from tempdate ; commit;
END;
select * from table(get_tab_tf) -- it will populate and then delete
select * from tempdate --you can check here result of deleting
you can use below query
select * from Table_demo delete from Table_demo
The feature you seek is SERIALIZABLE ISOLATION LEVEL. This feature enables repeatable reads, which in particular guarantee that both SELECTand DELETEwill read and process the same identical data.
Example
Alter session set isolation_level=serializable;
select * from tempdate;
--- now insert from other session a new record
delete from tempdate ;
commit;
-- re-query the table old records are deleted, new recor preserved.
I would like to preface this by saying I am VERY new to SQL, but my work now requires that I work in it.
I have a dataset containing topographical point data (x,y,z). I am trying to build a KNN model based on this data. For every point 'P', I search for the 100 points in the data set nearest P (nearest meaning geographically nearest). I then average the values of these points (this average is known as a residual), and add this value to the table in the 'resid' column.
As a proof of concept, I am trying to simply iterate over the table, and set the value of the 'resid' column to 1.0 in every row.
My query is this:
CREATE OR REPLACE FUNCTION LoopThroughTable() RETURNS VOID AS '
DECLARE row table%rowtype;
BEGIN
FOR row in SELECT * FROM table LOOP
SET row.resid = 1.0;
END LOOP;
END
' LANGUAGE 'plpgsql';
SELECT LoopThroughTable() as output;
This code executes and returns successfully, but when I check the table, no alterations have been made. What is my error?
Doing updates row-by-row in a loop is almost always a bad idea and will be extremely slow and won't scale. You should really find a way to avoid that.
After having said that:
All your function is doing is to change the value of the column value in memory - you are just modifying the contents of a variable. If you want to update the data you need an update statement:
You need to use an UPDATE inside the loop:
CREATE OR REPLACE FUNCTION LoopThroughTable()
RETURNS VOID
AS
$$
DECLARE
t_row the_table%rowtype;
BEGIN
FOR t_row in SELECT * FROM the_table LOOP
update the_table
set resid = 1.0
where pk_column = t_row.pk_column; --<<< !!! important !!!
END LOOP;
END;
$$
LANGUAGE plpgsql;
Note that you have to add a where condition on the primary key to the update statement otherwise you would update all rows for each iteration of the loop.
A slightly more efficient solution is to use a cursor, and then do the update using where current of
CREATE OR REPLACE FUNCTION LoopThroughTable()
RETURNS VOID
AS $$
DECLARE
t_curs cursor for
select * from the_table;
t_row the_table%rowtype;
BEGIN
FOR t_row in t_curs LOOP
update the_table
set resid = 1.0
where current of t_curs;
END LOOP;
END;
$$
LANGUAGE plpgsql;
So if I execute the UPDATE query after the loop has finished, will that commit the changes to the table?
No. The call to the function runs in the context of the calling transaction. So you need to commit after running SELECT LoopThroughTable() if you have disabled auto commit in your SQL client.
Note that the language name is an identifier, do not use single quotes around it. You should also avoid using keywords like row as variable names.
Using dollar quoting (as I did) also makes writing the function body easier
I'm not sure if the proof of concept example does what you want. In general, with SQL, you almost never need a FOR loop. While you can use a function, if you have PostgreSQL 9.3 or later, you can use a LATERAL subquery to perform subqueries for each row.
For example, create 10,000 random 3D points with a random value column:
CREATE TABLE points(
gid serial primary key,
geom geometry(PointZ),
value numeric
);
CREATE INDEX points_geom_gist ON points USING gist (geom);
INSERT INTO points(geom, value)
SELECT ST_SetSRID(ST_MakePoint(random()*1000, random()*1000, random()*100), 0), random()
FROM generate_series(1, 10000);
For each point, search for the 100 nearest points (except the point in question), and find the residual between the points' value and the average of the 100 nearest:
SELECT p.gid, p.value - avg(l.value) residual
FROM points p,
LATERAL (
SELECT value
FROM points j
WHERE j.gid <> p.gid
ORDER BY p.geom <-> j.geom
LIMIT 100
) l
GROUP BY p.gid
ORDER BY p.gid;
Following is a simple example to update rows in a table:
Assuming the row id field id
Update all rows:
UPDATE my_table SET field1='some value'
WHERE id IN (SELECT id FROM staff)
Selective row update
UPDATE my_table SET field1='some value'
WHERE id IN (SELECT id FROM staff WHERE field2='same value')
You don't need a function for that.
All you need is to run this query:
UPDATE table SET resid = 1.0;
if you want to do it with a function you can use SQL function:
CREATE OR REPLACE FUNCTION LoopThroughTable()
RETURNS VOID AS
$BODY$
UPDATE table SET resid = 1.0;
$BODY$
LANGUAGE sql VOLATILE
if you want to use plpgsql then function would be:
CREATE OR REPLACE FUNCTION LoopThroughTable()
RETURNS void AS
$BODY$
begin
UPDATE table SET resid = 1.0;
end;
$BODY$
LANGUAGE plpgsql VOLATILE
Note that it is not recommended to use plpgsql functions for tasks that can be done with Sql functions.