I'm using sqlite3 on my Rails project and I need to create a trigger that automatically inserts into the table when another referencing table is updated.
For example, I have 2 tables Breakdown and Total, schemas for each table are as below.
Breakdown
Date TEXT NOT NULL,
Amount DECIMAL NOT NULL
Total
Date TEXT NOT NULL,
Daily_Total DECIMAL NOT NULL,
FOREIGN KEY (Date) REFERENCES Breakdown(Date)
Then, below is my trigger creation.
CREATE TRIGGER update_sum AFTER INSERT ON Breakdown
...> BEGIN
...> INSERT OR REPLACE INTO Total (Date, Daily_Total)
...> VALUES (Breakdown.Date,
...> (SELECT SUM(Amount) FROM Breakdown WHERE Date = Total.Date));
...> END;
So, my idea is when I insert into Breakdown table as **INSERT INTO Breakdown VALUES (Date('now'),19.99);** then Total table gets updated by either inserting or update.
However, when I insert into Breakdown table, I get an error saying Error: no such column: Breakdown.Date
Can anyone direct me to the point where I'm doing wrong, please?
Thank you!
You can access the values of the row that caused the trigger to trigger, but that 'table' is called NEW:
INSERT ... VALUES(NEW.Date, (SELECT SUM... WHERE Date = NEW.Date));
Related
I'm in trouble with the implementation of a trigger.
Assuming that I have two types:
CREATE TYPE customer_t AS OBJECT(
code INTEGER,
name VARCHAR(20),
surname VARCHAR(20),
age INTEGER);
and the type
CREATE TYPE ticket_t AS OBJECT (
price INTEGER,
cust REF customer_t
)
And then I have the associate tables:
CREATE TABLE customers OF TYPE customer_t
CREATE TABLE tickets OF TYPE ticket_t
I have to do an exercise so I have to create a trigger for ensure that a customer won't buy more than 10 tickets but, if I use command like "select count(*)" I get an error because I can't access to mutating table.
Please can anyone help me with this trigger?
EDIT:
I populated the tables as follows:
INSERT INTO custs (code, name, surname, age) values (123, 'Paolo', 'Past', 32);
and repeating the following operation ten times:
INSERT INTO tickets (price, cust) values
(4, (SELECT * FROM (SELECT REF(T) FROM custs T WHERE name = 'Paolo' AND surname = 'Past') WHERE rownum < 2))
The trigger implemented is:
create or replace
trigger check_num_ticket after insert on tickets
for each row
declare
num_ticket number;
begin
SELECT count(*) INTO num_ticket FROM tickets WHERE :new.cust = cust;
if (num_ticket >= 10) then
raise_application_error('-20099', 'no ticket available');
end if;
end;
And I get this error:
A trigger (or a user defined plsql function that is referenced in
this statement) attempted to look at (or modify) a table that was
in the middle of being modified by the statement which fired it.
You are getting the mutating table error, because you are inserting in the same table where you want to get the row count for. Imagine your insert statement inserts two rows. There is no rule which row to insert first and which last, but your trigger fires on one inserted row and wants to know how many rows are already in the table. The DBMS tells you this is undefined, as the table is currently mutating.
You need an after statement trigger instead of a before row trigger. So when the insert statement's inserts are done, you look at the table to see whether there are suddenly customers with too many rows in it.
(A great alternative is a compound trigger. It combines row and statement triggers. So in the after row section you'd remember the customers in some array/collection and in the after statement section you'd look up the table for only the remembered customers.)
I have a requirement where I do a daily load from a view to a table. After the initial load, there may be scenarios where the original records get deleted from the view's source table. There are also scenarios where these records are updated.
When the stored procedure is run, the table that is loaded should pick up delta records. This means only new inserts. Also, it should mark deleted lines as D. In addition to this, any updates in source data must also updated in this table and marked as U.
Please refer to the attached image which shows in case 1 , 2 inserts on the initial load and then an update and then a delete.
Left side represents the view and right side represents the table I am trying to load.
Thanks!
Shyam
If you prefer to use triggers on HANA database tables you can use following samples on a column table, if you are working with row tables then you can prefer statement based approach
create trigger Salary_A_DEL after DELETE on Salary
REFERENCING OLD ROW myoldrow
FOR EACH ROW
begin
INSERT INTO SalaryLog (
Employee,
Salary,
Operation,
DateTime
) VALUES (
:myoldrow.Employee,
:myoldrow.Salary,
'D',
CURRENT_DATE
);
end;
create trigger Salary_A_UPD after UPDATE on Salary
REFERENCING NEW ROW mynewrow, OLD ROW myoldrow
FOR EACH ROW
begin
INSERT INTO SalaryLog (
Employee,
Salary,
Operation,
DateTime
) VALUES (
:mynewrow.Employee,
:mynewrow.Salary,
'U',
CURRENT_DATE
);
end;
create trigger Salary_A_INS after INSERT on Salary
REFERENCING NEW ROW mynewrow
FOR EACH ROW
begin
INSERT INTO SalaryLog (
Employee,
Salary,
Operation,
DateTime
) VALUES (
:mynewrow.Employee,
:mynewrow.Salary,
'I',
CURRENT_DATE
);
end;
I am using Access 2013 and I am trying to insert rows to a table but I don't want any duplicates. Basically if not exists in table enter the data to table. I have tried to using 'Not Exists' and 'Not in' and currently it still does not insert to table. Here is my code if I remove the where condition then it inserts to table but If I enter same record it duplicates. Here is my code:
INSERT INTO [UB-04s] ( consumer_id, prov_id, total_charges, [non-covered_chrgs], patient_name )
VALUES ([Forms]![frmHospitalEOR]![client_ID], [Forms]![frmHospitalEOR]![ID], Forms![frmHospitalEOR].[frmItemizedStmtTotals].Form.[TOTAL BILLED], Forms![frmHospitalEOR].[frmItemizedStmtTotals].Form.[TOTAL BILLED], [Forms]![frmHospitalEOR]![patient_name])
WHERE [Forms]![frmHospitalEOR]![ID]
NOT IN (SELECT DISTINCT prov_id FROM [UB-04s]);
You cannot use WHERE in this kind of SQL:
INSERT INTO tablename (fieldname) VALUES ('value');
You can add a constraint to the database, like a unique index, then the insert will fail with an error message. It is possible to have multiple NULL values for several rows, the unique index makes sure that rows with values are unique.
To avoid these kind of error messages you can build a procedure or use code to check data first, and then perform some action - like do the insert or cancel.
This select could be used to check data:
SELECT COUNT(*) FROM [UB-04s] WHERE prov_id = [Forms]![frmHospitalEOR]![ID]
It will return number of rows with the spesific value, if it is 0 then you are redy to run the insert.
Is it possible to have a non-primary key to be auto-incremented with every insertion?
For example, I want to have a log, where every log entry has a primary key (for internal use), and a revision number ( a INT value that I want to be auto-incremented).
As a workaround, this could be done with a sequence, yet I believe that sequences are not supported in SQLite.
You can do select max(id)+1 when you do the insertion.
For example:
INSERT INTO Log (id, rev_no, description)
VALUES ((SELECT MAX(id) + 1 FROM log), 'rev_Id', 'some description')
Note that this will fail on an empty table since there won't be a record with id is 0 but you can either add a first dummy entry or change the sql statement to this:
INSERT INTO Log (id, rev_no, description)
VALUES ((SELECT IFNULL(MAX(id), 0) + 1 FROM Log), 'rev_Id', 'some description')
SQLite creates a unique row id (rowid) automatically. This field is usually left out when you use "select * ...", but you can fetch this id by using "select rowid,* ...". Be aware that according to the SQLite documentation, they discourage the use of autoincrement.
create table myTable ( code text, description text );
insert into myTable values ( 'X', 'some descr.' );
select rowid, * from myTable;
:: Result will be;
1|X|some descr.
If you use this id as a foreign key, you can export rowid - AND import the correct value in order to keep data integrity;
insert into myTable values( rowid, code text, description text ) values
( 1894, 'X', 'some descr.' );
You could use a trigger (http://www.sqlite.org/lang_createtrigger.html) that checks the previous highest value and then increments it, or if you are doing your inserts through in a stored procedure, put that same logic in there.
My answer is very similar to Icarus's so I no need to mention it.
You can use Icarus's solution in a more advanced way if needed. Below is an example of seat availiabilty table for a train reservation system.
insert into Availiability (date,trainid,stationid,coach,seatno)
values (
'11-NOV-2013',
12076,
'SRR',
1,
(select max(seatno)+1
from Availiability
where date='11-NOV-2013'
and trainid=12076
and stationid='SRR'
and coach=1)
);
You can use an AFTER INSERT trigger to emulate a sequence in SQLite (but note that numbers might be reused if rows are deleted). This will make your INSERT INTO statement a lot easier.
In the following example, the revision column will be auto-incremented (unless the INSERT INTO statement explicitly provides a value for it, of course):
CREATE TABLE test (
id INTEGER PRIMARY KEY NOT NULL,
revision INTEGER,
description TEXT NOT NULL
);
CREATE TRIGGER auto_increment_trigger
AFTER INSERT ON test
WHEN new.revision IS NULL
BEGIN
UPDATE test
SET revision = (SELECT IFNULL(MAX(revision), 0) + 1 FROM test)
WHERE id = new.id;
END;
Now you can simply insert a new row like this, and the revision column will be auto-incremented:
INSERT INTO test (description) VALUES ('some description');
I got the following trigger on my sql server 2008 database
CREATE TRIGGER tr_check_stoelen
ON Passenger
AFTER INSERT, UPDATE
AS
BEGIN
IF EXISTS(
SELECT 1
FROM Passenger p
INNER JOIN Inserted i on i.flight= p.flight
WHERE p.flight= i.flightAND p.seat= i.seat
)
BEGIN
RAISERROR('Seat taken!',16,1)
ROLLBACK TRAN
END
END
The trigger is throwing errors when i try to run the query below. This query i supposed to insert two different passengers in a database on two different flights. I'm sure both seats aren't taken, but i can't figure out why the trigger is giving me the error. Does it have to do something with correlation?
INSERT INTO passagier VALUES
(13392,5315,3,'Janssen Z','2A','October 30, 2006 10:43','M'),
(13333,5316,2,'Janssen Q','2A','October 30, 2006 11:51','V')
UPDATE:
The table looks as below
CREATE TABLE Passagier
(
passengernumber int NOT NULL CONSTRAINT PK_passagier PRIMARY KEY(passagiernummer),
flight int NOT NULL CONSTRAINT FK_passagier_vlucht REFERENCES vlucht(vluchtnummer)
ON UPDATE NO ACTION ON DELETE NO ACTION,
desk int NULL CONSTRAINT FK_passagier_balie REFERENCES balie(balienummer)
ON UPDATE NO ACTION ON DELETE NO ACTION,
name varchar(255) NOT NULL,
seat char(3) NULL,
checkInTime datetime NULL,
gender char(1) NULL
)
There are a few problems with this subquery:
SELECT 1
FROM Passenger p
INNER JOIN Inserted i on i.flight= p.flight
WHERE p.flight= i.flight AND p.seat= i.seat
First of all, the WHERE p.flight = i.flight is quite unnecessary, as it's already part of your join.
Second, the p.seat = i.seat should also be part of the JOIN.
Third, this trigger runs after the rows have been inserted, so this will always match, and your trigger will therefore always raise an error and roll back.
You can fix the trigger, but a much better method would be to not use a trigger at all. If I understand what you're trying to do correctly, all you need is a UNIQUE constraint on flight, seat:
ALTER TABLE passgier
ADD CONSTRAINT IX_passagier_flightseat
UNIQUE (flight, seat)
If you run your trigger after inserting a record, and then look for a record with the values you just inserted, you will always find it. You might try an INSTEAD OF trigger so you can check for an existing records before actually doing the insert.
It might be throwing the error by finding itself in the table (circular reference back to itself). You might want to add an additional filter to the where clause like " AND Passenger.ID <> inserted.ID "