For my school project I need to add a trigger to my SQL Server database. I decided a 'no double usernames' trigger on my Users table would be relevant.
The problem is, that this trigger is firing every time I execute an INSERT query. I can't figure out why this is happening every time. I even tried different ways of writing my trigger.
The trigger I have now:
CREATE TRIGGER [Trigger_NoDuplicates]
ON [dbo].[Users]
FOR INSERT
AS
BEGIN
SET NOCOUNT ON
IF(EXISTS(SELECT Username FROM Users
WHERE Username = (SELECT Username FROM inserted)))
BEGIN;
RAISERROR('This username already exists!',15, 0)
ROLLBACK
END
END
Thanks in advance!
A trigger always fires every time, do you mean "raises an error every time"?
You currently have the following (expanded to multiple lines to make it clearer)...
IF (
EXISTS (
SELECT Username
FROM users
WHERE Username = (SELECT Username FROM inserted)
)
)
The key point here is the name of the table inserted. Past tense. It's already happened.
Anything in the inserted table has already been inserted into the target table.
So, what you need to check is that the username is in the target table more than once already.
However, it is possible to insert more than one record in to a table at once. This means that Username = (SELECT Username FROM inserted) will cause its own error. (You can't compare a single value to a set of values, and inserted can contain more than one row => more than one username...)
This is how I would approach your trigger...
IF EXISTS (
SELECT
users.Username
FROM
users
INNER JOIN
inserted
ON inserted.Username = users.Username
GROUP BY
users.Username
HAVING
COUNT(*) > 1
)
This takes the (already inserted in to) users table, and picks out all the records that mach username with any record in the inserted table.
Then it GROUPs them by they username field.
Then it filters the results to only include groups with more than 1 record.
These groups (usernames), have duplicate entries and should cause your trigger to raise an error.
An alternative is a bit more similar to your approach, but many people won't recognise it, so I generally wouldn't recommend it...
IF EXISTS (
SELECT
users.Username
FROM
users
WHERE
users.Username = ANY (SELECT username FROM inserted)
GROUP BY
users.Username
HAVING
COUNT(*) > 1
)
The ANY keyword gets very rarely used, but does what it sounds like. It allows a single value to be compared to a set of values.
Finally, if your table has an IDENTITY column, you can avoid the GROUP BY by explicitly stating you don't want to compare a row to itself...
IF EXISTS (
SELECT
users.Username
FROM
users
INNER JOIN
inserted
ON inserted.Username = users.Username
AND inserted.id <> users.id
)
Related
I am trying to delete all voters from a voters table where they are not registered as a democrat or republican AND only voted once. I have a database with three tables, congress_members, voters, and votes and have to JOIN votes with voters in order to delete the right data.
This code finds the data I want to delete:
SELECT voters.*
FROM voters JOIN votes ON voters.id = votes.voter_id
WHERE party = 'green' OR party = 'na' OR party = 'independent'
GROUP BY votes.voter_id
HAVING COUNT(*) = 1;
But I am unable to delete it because I am getting an error everytime I try to delete with a JOIN statement
You can phrase this as a delete with a where clause:
delete from voters
where votes.party not in ('democrat', 'republican') and
voters.id in (select id from votes group by id having count(*) = 1);
You are getting the error because the join will query your database and create a temporary table that will hold your newly queried data. The delete staements are used to remove data that is stored inside your database on your disk and not inside your memory.
The delete statement syntax is "DELETE FROM table WHERE conditions". The table value will need to be one of the three tables in your database, and your target is voters. As of right now, you have half of your delete statement complete.
The where clause needs to evaluate to a boolean value for each row. There is a function called EXISTS (). This function can be used to delete this data. Essentially, you will place your select statement from your post inside of the EXISTS (). The function will compare each of your rows in the target delete table to a row in your table inside of exists. If there is a match, then the row exists, the function evaluates to true for that row, and it is deleted.
DELETE FROM voters
WHERE (party = 'green' OR party = 'na' OR party = 'independent')
AND EXISTS (
SELECT 1 FROM votes WHERE votes.id = voters.id
HAVING COUNT(*) = 1
)
I have 3 tables that I am currently working with. USER, WORKSTATION and USER_WORKSTATION (basically a temp table).
My
USER table consists of user_id and user_name,
WORKSTATION consists of workstation_id, workstation_name and user_id.
As of right now, the user_id column is empty for all workstations and that is my problem.
I have created a table (imported from excel) USER_WORKSTATION. It consists of only user_names and their corresponding workstation(s). Is there someway that I can write an update query that will update the WORKSTATION table with the user_id found in the USER table based on the user_name and workstation_name combination in the USER_WORKSTATION table? I do not have any constraints currently set up and I'm using Oracle.
You can use the MERGE statement for this:
MERGE
INTO WORKSTATION W1
USING (SELECT W2.rowid AS rid, U.user_id
FROM USER_WORKSTATION UW
JOIN USER U
ON UW.user_name = U.user_name
JOIN WORKSTATION W2
ON UW.workstation_name = W2.workstation_name
) q
ON (W1.rowid = q.rid)
WHEN MATCHED THEN
UPDATE
SET W1.user_id = q.user_id;
You can do an UPDATE as well, it's a little messier.
See Update statement with inner join on Oracle
Hi try this plsql block.
I Suppose one user one workstation.
Declare
user_id User.userid%type;
ws_name WorkStationUser.wsname%type;
Cursor WSUSER is select * from WorkStationUser;
user_name WorkStationUser.username%type;
Begin
Open WSUSER;
Loop
Fetch WSUSER into user_name, ws_name;
select userid into user_id from USER where username=user_name;
select wsname into ws_name from WORKSTATIONUSER where username=user_name;
update WORKSTATION set userid=user_id whrer wsname=ws_name;
EXIT WHEN WSUSER%notfound;
END LOOP;
close WSUSER;
END;
I have tried it but not successful so far. Since my knowledge in query is limited, I thought I will better post it here.
I have students table with the following structure
create table students(
id int not null primary key identity,
sname varchar(25),
status varchar(25),
renew varchar(15),
enrollment datetime,
)
I have a number of students who has an ID, studentName(sname),status('active' or 'not-active'), renew('no' for new student, yes' for renewed student) and enrollment date.
insert into students values('jay','active','no','2010-01-01')
insert into students values('Phil','active','no','2010-01-01')
insert into students values('Cru','active','no','2010-01-01')
insert into students values('slow','active','no','2010-01-01')
insert into students values('true','active','no','2010-01-01')
insert into students values('false','active','no','2010-01-01')
Now I have an INSERT Trigger which is suppose to deactive an old student when a student is renewed. So if I insert the following which has renewal set to 'yes', it should make the already existing record 'inactive'.
insert into students values('false','active','yes','2011-01-01')
I wrote this INSERT Trigger and it works but it in-actives the old and the new inserted record both. I want only the original record to be inactivated. Also not that only enrollment date and nenew fields are different, the rest are the same between original and insert records. How to fix this? Here is my trigger
set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
GO
CREATE TRIGGER [dbo].[tr_renew_student]
ON [dbo].students
-- WITH ENCRYPTION
FOR INSERT
-- WITH APPEND
-- NOT FOR REPLICATION
AS
-- insert sql here
if exists(select * from inserted where Renew = 'yes')
BEGIN
UPDATE students
SET status = 'Inactive'
FROM Inserted i
INNER JOIN students T2
ON i.sname = T2.sname
END
Note that this is close approximation to my problem. Thank you
Change your update to this:
UPDATE students
SET status = 'Inactive'
FROM Inserted i
INNER JOIN students T2
ON i.sname = T2.sname
AND i.id <> t2.id
This checks that the row you are updating is NOT the newly inserted row.
Have you looked at ##identity? Years back I dealt with something similar and used ##identity to get the last created identity value; basically getting the latest identity value then setting all the records matching the criteria except the one with the ID returned via ##identity.
Read about the identity value getters here:
http://blog.sqlauthority.com/2007/03/25/sql-server-identity-vs-scope_identity-vs-ident_current-retrieve-last-inserted-identity-of-record/
Added: You're right about the inserted table. If you didn't want to / can't use the inserted table, your trigger could look something like this.
SELECT ##identity // <- this gets the last identity value inserted.
UPDATE students
SET status = 'Inactive'
WHERE students.name = (SELECT name FROM students WHERE id = ##identity)
AND id <> ##identity
Note: written from memory and not tested.
I am currently using a SQL Server Agent job to create a master user table for my in-house web applications, pulling data from 3 other databases; Sharepoint, Practice Management System and Our HR Database.
Currently it goes...
truncate table my_tools.dbo.tb_staff
go
insert into my_tools.dbo.tb_staff
(username
,firstname
,surname
,chargeoutrate)
select right(wss.nt_user_name,
,hr.firstname
,hr.surname
,pms.chargeoutrate
from sqlserver.pms.dbo.staff as pms
inner join sqlserver.wss_content.dbo.vw_staffwss as wss
on pms.nt_user_name = wss.nt_user_name
inner join sqlserver.hrdb.dbo.vw_staffdetails as hr
on wss.fullname = hr.knownas
go
The problem is that the entire table is cleared as the first step so my auto increment primary key/identified on tb_staff is certain to change. Also if someone is removed from sharepoint or the PMS they will not be recreated on this table and this will cause inconsistencies throughout the database.
I want to preserve entries in this table, even after they are removed from one of the other systems.
I suppose what I want to do is:
1) Mark all exiting entries in tb_staff as inactive (using a column called active and set it to false)
2) Run the query on the three joined tables and update every found record, also marking them as active.
I can't see how I can nest a select statement within an Update statement like I have here with the Insert statement.
How can I achieve this please?
*please note I have edited my SQL down to 4 columns and simplified it so small errors are probably due to rushed editing. The real query is far bigger.
WITH source AS(
SELECT RIGHT(wss.nt_user_name, 10) nt_user_name, /*Or whatever - this is invalid in the original SQL*/
hr.firstname,
hr.surname,
pms.chargeoutrate
FROM staff AS pms
INNER JOIN vw_staffwss AS wss
ON pms.nt_user_name = wss.nt_user_name
INNER JOIN vw_staffdetails AS hr
ON wss.fullname = hr.knownas
)
MERGE
INTO tb_staff
USING source
ON source.nt_user_name= tb_staff.username /*Or whatever you are using as the key */
WHEN MATCHED
THEN UPDATE SET active=1 /*Can synchronise other columns here if needed*/
WHEN NOT MATCHED BY TARGET
THEN INSERT (username, firstname, surname, chargeoutrate, active) VALUES (nt_user_name,firstname, surname, chargeoutrate, 1)
WHEN NOT MATCHED BY source
THEN UPDATE SET active=0;
Ok, so you have something like this working. You Insert into a table from a tmp table, where the Equipment Number and the Account Number are missing...
Insert INTO ClientEquipments(
SUB_ACCT_NO_SBB,
EquipmentDate,
EquipmentText,
EquipmentNumber)
Select
replace(a.SUB_ACCT_NO_SBB,'"','') as SUB_ACCT_NO_SBB,
getdate() as edate,'' as etext,
replace(a.equipmentNumber,'"','') equipmentNumber
from clientspaymenttemp a
where not exists
(select b.equipmentNumber
from clientEquipments b
where b.sub_acct_no_sbb=replace(a.SUB_ACCT_NO_SBB,'"','') and b.equipmentNumber=replace(a.equipmentNumber,'"',''))
group by SUB_ACCT_NO_SBB,equipmentNumber
But found a problem if the Equipment Number belonged to a different account number before, then my previous query will insert a new row, with the same Equipment Number but a new Account Number.
What I need it to do is simple:
If Account Number and Equipment Number exists, leave it alone no need to insert.
If Equipment Number exists, but it's assigned to a different Account Number, delete the old row. (Import file handles assignments so I am 100% sure that it needs to be assigned to new account)
Something Like this added somewhere in the previous code:
DELETE FROM ClientEquipments
WHERE (clientEquipmentId =
(SELECT clientEquipmentId
FROM ClientEquipments AS ClientEquipments_1
WHERE (equipmentNumber = '0012345CAEC6')))
If nothing exists then Insert a new row.
:::EDIT SOME MORE INFORMATION TO HELP ME OUT:::
I am reading a CSV file:
Sample Data:
Account | Name | Address | Some Extra Stuff | Equipment Number
"1234","First1,Last1","Address 1",etc etc... "ENum1234"
"1234","First1,Last1","Address 1",etc etc... "ENum5678"
"5678","First2,Last2","Address 2",etc etc... "ENum9123"
"9123","First3,Last3","Address 3",etc etc... "ENum4567"
This gets bulked imported into a temp table. (dbo.clients_temp)
Notice how account 1234 has 2 equipment numbers.
From here I insert new accounts into dbo.clients by doing a query from dbo.clients_temp to dbo.clients
Then I update dbo.clients with new information from dbo.clients_temp (ie Account 1234 might exists but now they have a new address.)
Now that my dbo.clients table is update with new clients, and new information for existing clients, I need to update my dbo.equipments table. I was originally doing what you see above, Insert Where Not Exists Account Number and Equipment Number.
Now the problem is that since equipments do change accounts, for example, Account Number 5678 might have become inactive which I don't track or care for at the database level, but the equipment Number might now belong to Account Number 1234. In this case, my original query will insert a new row into the database, since Account 1234 and Equipment Number are not returned in the SELECT.
Ok, I have lost this now :P I will try and revisit the question later on the weekend because I just confused myself O.o
I had to modify Gordon's answer above a bit, but that did the trick...
Below is the relevant line of code that deletes the inactive accounts.
DELETE FROM ClientEquipments WHERE EquipmentNumber =
(SELECT E.equipmentNumber FROM ClientEquipments As E INNER JOIN ClientsPaymentTemp AS T
on E.equipmentNumber = T.equipmentNumber and e.SUB_ACCT_NO_SBB <> T.SUB_ACCT_NO_SBB)
-- Fix Account Numbers and Equipment Numbers
update ClientPaymentTemp
set SUB_ACCT_NO_SBB = replace(SUB_ACCT_NO_SBB,'"',''),
equipmentNumber = replace(equipmentNumber,'"','')
-- Delete Existing Accounts Mapped to New Equipment
delete e
from ClientEquipments e
inner join clientspaymenttemp t
on e.EquipmentNumber = t.EquipmentNumber
and e.SUB_ACCT_NO_SBB <> t.SUB_ACCT_NO_SBB
-- Insert New Accounts
insert into ClientEquipments
(SUB_ACCT_NO_SBB,
EquipmentDate,
EquipmentText,
EquipmentNumber)
Select
SUB_ACCT_NO_SBB,
getdate() as edate,
'' as etext,
equipmentNumber
from ClientsPaymentTemp a
where not exists (select 1 from ClientEquipments where SUB_ACCT_NO_SBB = a.SUB_ACCT_NO_SBB and EquipmentNumber = a.EquipmentNumber)
I may be misunderstanding, but if all you're looking to do is delete a record where the account number isn't equal to something and the equipment number is equal to something, can't you just perform a delete with multiple where conditions?
Example:
DELETE FROM table
WHERE
equipmentNumber = someNumber AND
accountNumber <> someAccount
You could then get the number of rows affected using ##ROWCOUNT to check the number of rows affected and then insert if nothing was deleted. The example from the TechNet link above uses the following example:
USE AdventureWorks;
GO
UPDATE HumanResources.Employee
SET Title = N'Executive'
WHERE NationalIDNumber = 123456789
IF ##ROWCOUNT = 0
PRINT 'Warning: No rows were updated';
GO
I would think you could easily adapt that to do what you're looking to do.