Suppose in database i have some 1000 record of user , hisfriend, timeStampOfChat (i.e this are column)
Now for user (suppose subrata) , we have 30 friends name and its timestamp value. [so there are still 970 records of other user and their friends.]
Now i want to update a new data set where user subrata has 50 records out of which few are new and few are old. (for new it should insert the whole and for old it should update the time stamp.)
i want to use batch update/insert.
Now thats how i want to write the logic
if data base has user subrata then batch update time stamp where user = subrata
with this i will update the existing records but how to insert the new records out of that 50 record.
You haven't tagged this question with a RDBMS, but the correct way to do this in MySQL is an INSERT INTO...ON DUPLICATE KEY UPDATE query.
As long as you define an appropriate index, when the table already contains the row you're trying to insert, it will update the time instead of inserting a copy.
INSERT INTO table (user, hisfriend, timeStampOfChat) VALUES (1, 2, 3)
ON DUPLICATE KEY UPDATE timeStampOfChat = VALUES(timeStampOfChat)
Related
I have a table in MS access having more than 30 thousand rows.But in this table some values are duplicate so i delete duplicate rows and during this process autonumber fields also delete.Now i want to reset existing autonumber values using any query or vba code.
I use below mentioned query for reset values but query starts next value from one not resetting existing values.
ALTER TABLE [urlcheck] ALTER COLUMN [ID] COUNTER(1,1);
Currently auto number field values are just like this 1,2,5,7,9 now i want to reset values in this format 1,2,3,4,5
I have a table called YearTable with three columns (Year, Status, and LastUpdatedTime). Every time someone adds/updates a value into the year or status column LastUpdatedTime needs to be updated. I wrote a trigger for this, but now every time I try to add a new record I get an error message:
ErrorSource: .NetSqlClient Data Provider.
Error Message: Cannot insert the value NULL into Column 'Year', table 'Budget.YearTable'; column does not allow nulls. Insert fails.
This is the trigger:
CREATE TRIGGER UpdateTrigger
ON YearTable
AFTER INSERT,DELETE,UPDATE
AS
BEGIN
insert into tblaudit(LastUpdatedTime)
values(GETDATE())
END
GO
You stated:
I wrote a trigger for this, but now every time I try to add a new record I get an error message:
ErrorSource: .NetSqlClient Data Provider. Error Message: Cannot insert the value NULL into Column 'Year', table 'Budget.YearTable'; column does not allow nulls. Insert fails.
From this, does this mean your updates and deletes are working? If that is the case, then it sounds like just like the error message states. When you're doing an insert into the table, you aren't supplying a value for the year column on the YearTable.
Have you tried disabling the trigger and seeing if the behavior exists when doing the same operations?
After further consideration of your question, I'm now assuming you're meaning that when a row in YearTable is updated, that that same row in YearTable has its LastUpdated column updated. Though now I'm not really sure where your tblAudit is coming from. Or why you would have the trigger created for deletes when there would be no row to update at that point.
I'm going to assume that your key on the table is year - if you don't currently have a key, you probably need one.
To handle the LastUpdated for inserts/updates you could use the following in your trigger (assuming year is your key):
UPDATE YearTable
SET LastUpdated = GetDate()
FROM inserted
where YearTable.Year = inserted.year
I have a requirement as a trigger should get fired when any row is inserted or deleted from table FAB which contains num as unique value. and depending upon that num value, another table should be update.
e.g.
FAB table
num code trs
10 A2393 80
20 B3445 780
Reel table
reelnr num use flag
340345 10 500 1
when num 10 from FAB table gets deleted(or any new num gets inserted), the trigger should get fired and should check the reel table which contains that num value and give the reelnr.
How to proceed with this?
you can Use Inserted & Deleted Table in SQL
These two tables are special kind of table that are only available inside the scope of the triggers.
If you tries to use these tables outside the scope of Triggers then you will get Error.
Inserted : These table is use to get track of any new records that are insert in the table.
Suppose there are Six rows are inserted in your table then these table will consist of all the six rows that are inserted.
Deleted : These table is used to track all the Deleted record from your tables.
Last delete rows will be tracked by these table.
For Insert :
CREATE TRIGGER TR_AUDIT_Insert
ON Reel_table
FOR INSERT
AS
BEGIN
INSERT INTO Reel_table (reelnr, num, use, flag)
SELECT
reelnr,
num,
use,
flag
FROM
INSERTED
END
For Delete :
CREATE TRIGGER TR_AUDIT_Delete
ON Product
FOR DELETED
AS
BEGIN
INSERT INTO Reel_table (reelnr, num, use, flag)
SELECT
reelnr,
num,
use,
flag
FROM
DELETED
END
Note :
I don't know from where these three reelnr, use flag values you are getting
So, Please modify this as per your need.
This is the format of the Triggers that normally we use.
You also can do this by using single trigger also
I dont know what is your exact requirement
If you want to achieve by only single Trigger then you can refer this link :
Refer
I have written a Trigger which is transferring a record from a table members_new to members_old. The Function of trigger is to insert a record into members_old on after insert in members_new. So suppose a record is getting inserted into a members_new like
nMmbID nMmbName nMmbAdd
1 Abhi Bangalore
This record will get inserted into members_old with the same data structure of the table
My trigger is like :
create trigger add_new_record
after
insert on members_new
for each row
INSERT INTO `test`.`members_old`
(
`nMmbID`,
`nMmbName`,
`nMmbAdd`
)
(
SELECT
`members_new`.`nMmbID`,
`members_new`.`nMmbName`,
`members_new`.`nMmbAdd`
FROM `test`.`members_new`
where nMmbID = (select max(nMmbID) from `test`.`members_new` // written to read the last record from the members_new and stop duplication on the members_old , also this will reduce the chances of any error . )
)
This trigger is working for now , but my confusion is that what will happen if a multiple insertion is happening at one instance of time.
Will it reduce the performance?
Will I face deadlock condition ever in any case as my members_old have FKs?
If any better solution for this situation is there, please give limelight on that
From the manual:
You can refer to columns in the subject table (the table associated with the trigger) by using the aliases OLD and NEW. OLD.col_name refers to a column of an existing row before it is updated or deleted. NEW.col_name refers to the column of a new row to be inserted or an existing row after it is updated.
create trigger add_new_record
after
insert on members_new
for each row
INSERT INTO `test`.`members_old`
SET
`nMmbID` = NEW.nMmbID,
`nMmbName` = NEW.nMmbName,
`nMmbAdd` = NEW.nMmbAdd;
And you will have no problem with deadlocks or whatever. Also it should be much faster, because you don't have to read the max value before (which is also unsecure and might lead to compromised data). Read about isolation levels and transactions if you're interested why...
I am trying to create a database trigger that will update certain characters in a field for a table when a user inserts data into the table...
Ex.
ID EXCHANGE LEADRT
1 new L-3
2 new 3
3 new 5
So I would want to leave id 1 alone because the format for the LEADRT is correct but ids 2 and 3 are not.
CREATE TRIGGER triggerupdate ON PoleUnits FOR INSERT,
UPDATE AS
if not exists (select * from Poleunits where LEADRT like '%L-%')
update PoleUnits set LEADRT = STUFF (LEADRT, 1, 0,'L-');
Any ideas why I can't get this to work or better suggestions on how to accomplish this?
In insert and update triggers you have access to a specific table called inserted where the rows to be inserted/updated are held. Those are not real tables, they are just logical tables with the same structure as the table on which the trigger fired.
Your current logic works on the original table, thus working with all the existing data, but not with the data you are actually inserting, i.e. it will update everything except the data you actually want updated. Something like this could work:
CREATE TRIGGER triggerupdate ON PoleUnits
FOR INSERT, UPDATE AS
update PoleUnits
set LEADRT = STUFF (PoleUnits.LEADRT, 1, 0,'L-')
from PoleUnits
inner join inserted -- this is basically a self join
on PoleUnits.ID = inserted.ID
where PoleUnits.LEADRT not like '%L-%'
This will only update those rows in PoleUnits that are being inserted, and only if their LEADRT field is not in the L- format.