I have this question that I can see what it's asking but just can't wrap my head around how to write it specifically:
When a new tuple is inserted into the sales order detail, your trigger should insert a corresponding raw material tuple in the Inventory Report table for the Report date (i.e., beginning inventory level, consumption quantity, same-day order quantity, next-day order quantity)
Assumptions I gathered from the notes:
itemID = itemID from RAWMATERIALS table
reportDate = dueDate from SALESORDERS table
begInv = inventoryLevels from RAWMATERIALS table
consumpQty = itemID from FINISHEDGOODS * rmQuantity (raw material required to make each finished good) from FINISHED GOODS
orderNextDay = If consumpQty <= begInv then orderNextDay = consumpQty
orderSameDay = 0
orderSameDay = If consumpQty > begInv then orderNextDay = begInv
orderSameDay = consumpQty - begInv
I thought the trigger might go something like:
CREATE OR REPLACE TRIGGER inv_report
BEFORE INSERT
ON SALESORDERDETAIL
FOR EACH ROW
DECLARE
item_id RAWMATERIALS.ITEMID%TYPE
reportDate SALESORDERS.DUEDATE%TYPE
begInv RAWMATERIALS.INVENTORYLEVEL%TYPE
And then I understand we would probably need to INSERT into INVENTORYREPORT table (which currently has no data in it) and maybe do an IF ELSEIF statement to satisfy the orderNextDay and orderSameDay columns but i'm still not familiar enough with PL/SQL to know exactly how to tackle this.
Can anyone help me out with this? Thanks!
I'll try to find some time to write up some code for you on this, but my first recommendation is to NOT do this in a trigger. Instead, create a procedure "insert_so_detail" that inserts into the the SALESORDERDETAIL and then does the related insert into INVENTORYREPORT.
That procedure is then always called to insert into the S-O-D table. Executing DML inside triggers is a tricky thing to do because the database might decide it needs to restart the DML and then possibly do another insert into the I-R table. Check out this AskTOM thread for more details.
You are always better off putting your DML into PL/SQL package APIs, then only allow DML on the table through the API (grant execute on the package, do NOT grant insert or update or delete on the table directly to a user).
Related
Similar to this question and this solution for PostgreSQL (in particular "INSERT missing FK rows at the same time"):
Suppose I am making an address book with a "Groups" table and a "Contact" table. When I create a new Contact, I may want to place them into a Group at the same time. So I could do:
INSERT INTO Contact VALUES (
"Bob",
(SELECT group_id FROM Groups WHERE name = "Friends")
)
But what if the "Friends" Group doesn't exist yet? Can we insert this new Group efficiently?
The obvious thing is to do a SELECT to test if the Group exists already; if not do an INSERT. Then do an INSERT into Contacts with the sub-SELECT above.
Or I can constrain Group.name to be UNIQUE, do an INSERT OR IGNORE, then INSERT into Contacts with the sub-SELECT.
I can also keep my own cache of which Groups exist, but that seems like I'm duplicating functionality of the database in the first place.
My guess is that there is no way to do this in one query, since INSERT does not return anything and cannot be used in a subquery. Is that intuition correct? What is the best practice here?
My guess is that there is no way to do this in one query, since INSERT
does not return anything and cannot be used in a subquery. Is that
intuition correct?
You could use a Trigger and a little modification of the tables and then you could do it with a single query.
For example consider the folowing
Purely for convenience of producing the demo:-
DROP TRIGGER IF EXISTS add_group_if_not_exists;
DROP TABLE IF EXISTS contact;
DROP TABLE IF EXISTS groups;
One-time setup SQL :-
CREATE TABLE IF NOT EXISTS groups (id INTEGER PRIMARY KEY, group_name TEXT UNIQUE);
INSERT INTO groups VALUES(-1,'NOTASSIGNED');
CREATE TABLE IF NOT EXISTS contact (id INTEGER PRIMARY KEY, contact TEXT, group_to_use TEXT, group_reference TEXT DEFAULT -1 REFERENCES groups(id));
CREATE TRIGGER IF NOT EXISTS add_group_if_not_exists
AFTER INSERT ON contact
BEGIN
INSERT OR IGNORE INTO groups (group_name) VALUES(new.group_to_use);
UPDATE contact SET group_reference = (SELECT id FROM groups WHERE group_name = new.group_to_use), group_to_use = NULL WHERE id = new.id;
END;
SQL that would be used on an ongoing basis :-
INSERT INTO contact (contact,group_to_use) VALUES
('Fred','Friends'),
('Mary','Family'),
('Ivan','Enemies'),
('Sue','Work colleagues'),
('Arthur','Fellow Rulers'),
('Amy','Work colleagues'),
('Henry','Fellow Rulers'),
('Canute','Fellow Ruler')
;
The number of values and the actual values would vary.
SQL Just for demonstration of the result
SELECT * FROM groups;
SELECT contact,group_name FROM contact JOIN groups ON group_reference = groups.id;
Results
This results in :-
1) The groups (noting that the group "NOTASSIGNED", is intrinsic to the working of the above and hence added initially) :-
have to be careful regard mistakes like (Fellow Ruler instead of Fellow Rulers)
-1 used because it would not be a normal value automatically generated.
2) The contacts with the respective group :-
Efficient insertion
That could likely be debated from here to eternity so I leave it for the fence sitters/destroyers to decide :). However, some considerations:-
It works and appears to do what is wanted.
It's a little wasteful due to the additional wasted column.
It tries to minimise the waste by changing the column to an empty string (NULL may be even more efficient, but for some can be confusing)
There will obviously be an overhead BUT in comparison to the alternatives probably negligible (perhaps important if you were extracting every Facebook user) but if it's user input driven likely irrelevant.
What is the best practice here?
Fences again. :)
Note Hopefully obvious, but the DROP statements are purely for convenience and that all other SQL up until the INSERT is run once
to setup the tables and triggers in preparation for the single INSERT
that adds a group if necessary.
For my homework I need to make a package that contains a procedure that removes all records from the table dwdimartist and then fills the table with all records from the table artist and add a field with the date of today.
This is what I've created, it works but I don't know if it's performant enough. Is it better to use a cursor that loops over each record in the table artist?
CREATE OR REPLACE PACKAGE BODY dwh AS
PROCEDURE filldwh IS
today_date DATE := SYSDATE;
BEGIN
DELETE FROM dwdimartist;
INSERT INTO dwdimartist (artistkey, name) (SELECT artistid, name FROM artist);
UPDATE dwdimartist SET added = today_date;
END filldwh;
END dwh;
Simple SQL query like you did is better choice than a cursor or implicit loop.
possible improvement:
You should do it at once without update: set the date during insert.
INSERT INTO dwdimartist (artistkey, name, added)
(SELECT artistid, name, sysdate FROM artist);
Hope it helps
You don’t need to use cursors. You can hardly beat Insert ... select since it’s SQL itself and in most cases it works better than any programmatic structure due to native dbms optimization. However, you can do better if you decrease number of I/O operations. You don’t need update here. Simply add sysdate to your select and insert everything together.
insert into dwdimartist(artistkey, name, added) select artistid, name, sysdate from artist;
Another thing to improve is your ‘delete’. While it’s small table for learning purposes you won’t feel any difference between delete and truncate but for real ETL tasks and big tables you’ll see it definitely. Yes you cannot use truncate directly in your PL/SQL but there are 3 ways to do it:
execute immediate ‘truncate dwdimartist’;
Dbms_utility.exec_ddl_statement(‘truncate ...;’);
DBMS_SQL package
However, remember that calling truncate will execute commit like any ddl command. So delete may be the only option sometimes. But even if it is, you should avoid it for the whole table.
I am trying to build a simple hotel room check-in database as a learning exercise.
CREATE TABLE HotelReservations
(
roomNum INTEGER NOT NULL,
arrival DATE NOT NULL,
departure DATE NOT NULL,
guestName CHAR(30) NOT NULL,
CONSTRAINT timeTraveler CHECK (arrival < departure) /* stops time travelers*/
/* CONSTRAINT multipleReservations CHECK (my question is about this) */
PRIMARY KEY (roomNum, arrival)
);
I am having trouble specifying a constraint that doesn't allow inserting a new reservation for a room that has not yet been vacated. For example (below), guest 'B' checks into room 123 before 'A' checks out.
INSERT INTO HotelStays(roomNum, arrival, departure, guestName)
VALUES
(123, date("2017-02-02"), date("2017-02-06"), 'A'),
(123, date("2017-02-04"), date("2017-02-08"), 'B');
This shouldn't be allowed but I am unsure how to write this constraint. My first attempt was to write a subquery in check, but I had trouble figuring out the proper subquery because I don't know how to access the 'roomNum' value of a new insert to perform the subquery with. I then also figured out that most SQL systems don't even allow subquerying inside of check.
So how am I supposed to write this constraint? I read some about triggers which seem like it might solve this problem, but is that really the only way to do it? Or am I just dense and missing an obvious way to write the constraint?
The documentation indeed says:
The expression of a CHECK constraint may not contain a subquery.
While it would be possible to create a user-defined function that goes back to the database and queries the table, the only reasonable way to implement this constraint is with a trigger.
There is a special mechanism to access the new row inside the trigger:
Both the WHEN clause and the trigger actions may access elements of the row being inserted, deleted or updated using references of the form "NEW.column-name" and "OLD.column-name", where column-name is the name of a column from the table that the trigger is associated with.
CREATE TRIGGER multiple_reservations_check
BEFORE INSERT ON HotelReservations
BEGIN
SELECT RAISE(FAIL, "reservations overlap")
FROM HotelReservations
WHERE roomNum = NEW.roomNum
AND departure > NEW.arrival
AND arrival < NEW.departure;
END;
I want to write a stored procedure (SQL server 2008r2), say I have a table:
person
Columns:
Id int (pk)
Date_of_birth date not null
Phone int allow null
Address int allow null
Name nvarchat(50) not null
Sample data:
Id=1,Date_of_birth=01/01/1987,phone=88888888,address=null,name='Steve'
Update statement in Stored procedure, assume
The parameters are already declare:
Update person set
Date_of_birth=#dob,phone=#phone,address=#address,name=#name where id=#id
The table has a trigger to log any changes.
Now I have an asp.net update page for updating the above person table
The question is, if user just want to update address='apple street' , the above update statement will update all the fields but not check if the original value = new value, then ignore this field and then check the next field. So my log table will log all the event even the columns are not going to be updated.
At this point, my solutions
Select all the value by id and store them into local variables.
Using if-else check and generate the update statement. At last,
dynamically run the generated SQL (sp_executesql)
Select all the value by id and store them into local variables.
Using if-else check and update each field seperately:
If #dob <> #ori_dob
Begin
Update person set date_of_birth=#dob where id=#id
End
May be this is a stupid question but please advice me if you have better idea, thanks!
This is an answer to a comment by the OP and does not address the original question. It would, however, be a rather ugly comment.
You can use a statement like this to find the changes to Address within an UPDATE trigger:
select i.Id, d.Address as OldAddress, i.Address as NewAddress
from inserted as i inner join
deleted as d on d.Id = i.Id
where d.Address <> i.Address
One such statement would be needed for each column that you want to log.
You could accumulate the results of the SELECTs into a single table variable, then summarize the results for each Id. Or you can use INSERT/SELECT to save the results directly to your log table.
I would like to ask you how would you increase the performance on Insert cursor in this code?
I need to use dynamic plsql to fetch data but dont know how to improve the INSERT in best way. like Bulk Insert maybe?
Please let me know with code example if possible.
// This is how i use cur_handle:
cur_HANDLE integer;
cur_HANDLE := dbms_sql.open_cursor;
DBMS_SQL.PARSE(cur_HANDLE, W_STMT, DBMS_SQL.NATIVE);
DBMS_SQL.DESCRIBE_COLUMNS2(cur_HANDLE, W_NO_OF_COLS, W_DESC_TAB);
LOOP
-- Fetch a row
IF DBMS_SQL.FETCH_ROWS(cur_HANDLE) > 0 THEN
DBMS_SQL.column_value(cur_HANDLE, 9, cont_ID);
DBMS_SQL.COLUMN_VALUE(cur_HANDLE, 3, proj_NR);
ELSE
EXIT;
END IF;
Insert into w_Contracts values(counter, cont_ID, proj_NR);
counter := counter + 1;
END LOOP;
You should do database actions in sets whenever possible, rather than row-by-row inserts. You don't tell us what CUR_HANDLE is, so I can't really rewrite this, but you should probably do something like:
INSERT INTO w_contracts
SELECT ROWNUM, cont_id, proj_nr
FROM ( ... some table or joined tables or whatever... )
Though if your first value there is a primary key, it would probably be better to assign it from a sequence.
Solution 1) You can populate inside the loop a PL/SQL array and then just after the loop insert the whole array in one step using:
FORALL i in contracts_tab.first .. contracts_tab.last
INSERT INTO w_contracts VALUES contracts_tab(i);
Solution 2) if the v_stmt contains a valid SQL statement you can directly insert data into the table using
EXECUTE IMMEDIATE 'INSERT INTO w_contracts (counter, cont_id, proj_nr)
SELECT rownum, 9, 3 FROM ('||v_stmt||')';
"select statement is assembled from a website, ex if user choose to
include more detailed search then the select statement is changed and
the result looks different in the end. The whole application is a web
site build on dinamic plsql code."
This is a dangerous proposition, because it opens your database to SQL injection. This is the scenario in which Bad People subvert your parameters to expand the data they can retrieve or to escalate privileges. At the very least you need to be using DBMS_ASSERT to validate user input. Find out more.
Of course, if you are allowing users to pass whole SQL strings (you haven't provided any information regarding the construction of W_STMT) then all bets are off. DBMS_ASSERT won't help you there.
Anyway, as you have failed to give the additional information we actually need, please let me spell it out for you:
will the SELECT statement always have the same column names from the same table name, or can the user change those two?
will you always be interested in the third and ninth columns?
how is the W_STMT string assembled? How much control do you have over its projection?