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;
Related
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
)
I have 2 tables:
1. Tbl_Master: columns:
a. SEQ_id
b. M_Email_id
c. M_location_id
d. Del_flag
2. Tbl_User: columns
a. U_email_id
b. Last_logged_date
c. User_id
First table Is master table it has unique rows i.e. single record of all users in the system.
Each User can be uniquely identified by the email_id in each table.
One user can have multiple profile, which means for one us_email_id field in the tblUser table, there can be many user_id in tbl_User,
i.e there can be multiple entries in second table for each user.
Now I have to select only those users who have logged in for last time before, lets say '2012', i.e before 1-Jan-2012.
But if one user has 2 or more user_id and one user_id has last_logged_date less than 2012
But other user_id has greater than 2012 then such user should be ignored.
In the last all all the result user will be marked for deletion by setting DEL_flag in master table to ‘Yes’
For eg:
Record in Tbl_Master:
A123 ram#abc.com D234 No
A123 john#abc.com D256 No
Record in tbl_User can be Like:
ram#abc.com '11-Dec-2011' Ram1
ram#abc.com '05-Apr-2014' Ram2
john#abc.com '15-Dec-2010' John1
In such case only John's Record should be selected not of Ram whose one profile has last_logged_date>1-Jan-2012
Another possibility was
SELECT
m.M_Email_id,
MAX(u.Last_logged_date) AS last_login
FROM
Tbl_Master m
INNER JOIN
Tbl_User u on u.U_email_id = m.M_Email_id
GROUP BY m.M_Email_id
HAVING
-- Year(MAX(u.Last_logged_date)) < 2012 -- use the appropriate function of your DBMS
EXTRACT(YEAR FROM(MAX(u.Last_logged_date))) < 2012 -- should be the version for oracle
-- see http://docs.oracle.com/cd/B14117_01/server.101/b10759/functions045.htm#i1017161
Your UPDATE operation can use this select in the WHERE clause.
Try this, this ans is in sql server, I haven't worked on Oracle.
select * from Tbl_Master
outer apply
(
select U_email_id,max(Last_logged_date)as LLogged,count(U_email_id) as RecCount
from Tbl_User
where Tbl_User.U_email_id = Tbl_Master.M_Email_id
group by U_email_id
)as a
where RecCount >2
and Year(LLogged) < '2012'
Try this DEMO
Hope it helps you.
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 to migrate a large amount of existing data in a Postgres DB after a schema change.
In the old schema a country attribute would be stored in the users table. Now the country attribute has been moved into a separate address table:
users:
country # OLD
address_id # NEW [1:1 relation]
addresses:
id
country
The schema is actually more complex and the address contains more than just the country. Thus, every user needs to have his own address (1:1 relation).
When migrating the data, I'm having problems setting the foreign keys in the users table after inserting the addresses:
INSERT INTO addresses (country)
SELECT country FROM users WHERE address_id IS NULL
RETURNING id;
How do I propagate the IDs of the inserted rows and set the foreign key references in the users table?
The only solution I could come up with so far is creating a temporary user_id column in the addresses table and then updating the the address_id:
UPDATE users SET address_id = a.id FROM addresses AS a
WHERE users.id = a.user_id;
However, this turned out to be extremely slow (despite using indices on both users.id and addresses.user_id).
The users table contains about 3 million rows with 300k missing an associated address.
Is there any other way to insert derived data into one table and setting the foreign key reference to the inserted data in the other (without changing the schema itself)?
I'm using Postgres 8.3.14.
Thanks
I have now solved the problem by migrating the data with a Python/sqlalchemy script. It turned out to be much easier (for me) than trying the same with SQL. Still, I'd be interested if anybody knows a way to process the RETURNING result of an INSERT statement in Postgres SQL.
The table users must have some primary key that you did not disclose. For the purpose of this answer I will name it users_id.
You can solve this rather elegantly with data-modifying CTEs introduced with PostgreSQL 9.1:
country is unique
The whole operation is rather trivial in this case:
WITH i AS (
INSERT INTO addresses (country)
SELECT country
FROM users
WHERE address_id IS NULL
RETURNING id, country
)
UPDATE users u
SET address_id = i.id
FROM i
WHERE i.country = u.country;
You mention version 8.3 in your question. Upgrade! Postgres 8.3 has reached end of life.
Be that as it may, this is simple enough with version 8.3. You just need two statements:
INSERT INTO addresses (country)
SELECT country
FROM users
WHERE address_id IS NULL;
UPDATE users u
SET address_id = a.id
FROM addresses a
WHERE address_id IS NULL
AND a.country = u.country;
country is not unique
That's more challenging. You could just create one address and link to it multiple times. But you did mention a 1:1 relationship that rules out such a convenient solution.
WITH s AS (
SELECT users_id, country
, row_number() OVER (PARTITION BY country) AS rn
FROM users
WHERE address_id IS NULL
)
, i AS (
INSERT INTO addresses (country)
SELECT country
FROM s
RETURNING id, country
)
, r AS (
SELECT *
, row_number() OVER (PARTITION BY country) AS rn
FROM i
)
UPDATE users u
SET address_id = r.id
FROM r
JOIN s USING (country, rn) -- select exactly one id for every user
WHERE u.users_id = s.users_id
AND u.address_id IS NULL;
As there is no way to unambiguously assign exactly one id returned from the INSERT to every user in a set with identical country, I use the window function row_number() to make them unique.
Not as straight forward with Postgres 8.3. One possible way:
INSERT INTO addresses (country)
SELECT DISTINCT country -- pick just one per set of dupes
FROM users
WHERE address_id IS NULL;
UPDATE users u
SET address_id = a.id
FROM addresses a
WHERE a.country = u.country
AND u.address_id IS NULL
AND NOT EXISTS (
SELECT * FROM addresses b
WHERE b.country = a.country
AND b.users_id < a.users_id
); -- effectively picking the smallest users_id per set of dupes
Repeat this until the last NULL value is gone from users.address_id.
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;