Hello i have a question i assume mainly about SQL server functionality. Im building a test database and i have stumbled a problem when i try to insert data into my tables.
picture 1 shows the error message i get when trying to add rows.
https://i.stack.imgur.com/GW3C2.png
Picture 2 shows all relations in the database
//i.stack.imgur.com/7BhHa.png
picture 3 shows the table i am currently trying to update
//i.stack.imgur.com/3JqtA.png
In the table i have a combined primary key ("SDat" and "Kurs") The error message i get implyes that primary key must be uniqe, but what dont understand is since i have a third column "Elev" which makes the row uniqe, why wont SQL server me insert this row to table? I have tried making the same database in Acess and it works so i assume problem is something in SQL server
Regards Robert
A Primary Key by definition means the value must be unique. So if you have a combined primary key on 2 fields, then that value on those 2 fields needs to be unique meaning it can only have 1 row. If you need to enforce unique values on the combination of 3 fields (SDat, Kurs, and Elev) then your PK needs to include all 3 fields.
If you really need to enforce a unique constraint across alot of fields in a table, I wouldn't use a PK to enforce that, but instead use a UNIQUE constraint.
ALTER TABLE tablename ADD CONSTRAINT constraintname UNIQUE (column1, ..., columnn)
Then you can create a different column for your Primary Key so that as you add columns and need to require those additional columns be unique, you don't have to edit your PK and rebuild your table.
Related
There is one column named Line_no (smallint) now. I want to change this column data type is bigint ,but this column is primary key, and have so many tables has foreign key reference on it, so how to change it?, i need to change both Sql server and oracle database
First of all there's no easy way to do that currently. especially in Oracle, in order to change the data type, all the values of the field should be null. anyway the following process works for both Oracle and SQL Server:
make your database off line so that no operation can disturb our
process.
Add a new field, say line_num having your new data type.
update the the new field with the line_no values for all records.
write a Stored Procedure to drop all the FKs referencing current
PK, using meta data and this SP should write the add FK command to
dbms output, while it is looping, so that later you can execute them
to add these FKs again in step 9.
drop the primary key off the line_no field.
drop the field line_no.
rename the field
line_num to line_no.
add the primary key on the new field.
run the commands generated in step 4 to add all the FKs again.
make your db online :)
It depends on your DBMS. You may have to drop the foreign key constraints, alter the columns and re-create the constraints.
This question have been asked by several people but my problem seems to be different.
Actually I have to merge same structured tables from different databases in postgresql into a new DB. What I am doing is that I connect to remote db using dblink, reads that table in that db and insert it into the table in the current DB like below
INSERT INTO t_types_of_dementia SELECT * FROM dblink('host=localhost port=5432 dbname=snap-cadence password=xxxxxx', 'SELECT dementia_type, snapid FROM t_types_of_dementia') as x(dementia_type VARCHAR(256),snapid integer);
First time this query runs fine, but when I run it again or try to run it with some other remote database's table: it gives me this error
ERROR: duplicate key value violates unique constraint
"t_types_of_dementia_pkey"
I want that this new tables gets populated by entries of others tables from other dbs.
Some of the solutions proposed talks about sequence, but i am not using any
The structure of the table in current db is
CREATE TABLE t_types_of_dementia(
dementia_type VARCHAR(256),
snapid integer NOT NULL,
PRIMARY KEY (dementia_type,snapid)
);
P.S. There is a specific reason why both the columns are used as a primary key which may not be relevant in this discussion, because same issue happens in other tables where this is not the case.
As the error message tells you - you can not have two rows with the same value in the columns dementia_type, snapid since they need to be unique.
You have to make sure that the two databases has the same values for dementia_type, snapid.
A workaround would be to add a column to your table alter table t_types_of_dementia add column id serial generated always and use that as primary key instead of your current.
I am newbie to MSSQL Server and don't have any knowledge about it.
i have below question.
I have added nine records with same value as show per below image in SQL Server 2005.
i Have not given any primary key to Table.
Now when i selecting one record or multiple record and hit the delete key it does not delete the records from table instead it gives me error.
You need to add a primary key to uniquely identify each record, otherwise the SQL server has no way of distinguishing the records, and therefore no way of knowing which one to delete, causing an error.
That's because you don't have any primary key and server doesn't know which row to remove. Clear the table ( DELETE * FROM dbo.Patient ) and create new Id column as a primary key.
In MSSQL you need to have a primary key for the table. This will uniquely identify each row of that particular table.
For example in Oracle you don't need this as there you can use ROWID (meaning every row from every table has a unique ID in the database). Once you know this ID you Oracle knows for sure from which table it is.
So now you can add a primary key to the table and you can make it be auto-increment - ensuring uniqueness.
I need to make some changes to a SQL Server 2008 database.
This requires the creation of a new table, and inserting a foreign key in the new table that references the Primary key of an already existing table. So I want to set up a relationship between my new tblTwo, which references the primary key of tblOne.
However when I tried to do this (through SQL Server Management Studio) I got the following error:
The columns in table 'tblOne' do not
match an existing primary key or
UNIQUE constraint
I'm not really sure what this means, and I was wondering if there was any way around it?
It means that the primary key in tblOne hasn't been properly declared - you need to go to tblOne and add the PRIMARY KEY constraint back onto it.
If you're sure that tblOne does have a PRIMARY KEY constraint, then maybe there are multiple tblOne tables in your DB, belonging to different schemas, and your references clause in your FK constraint is picking the wrong one.
If there's a composite key (which your comment would indicate), then you have to include both columns in your foreign key reference also. Note that a table can't have multiple primary keys - but if it has a composite key, you'll see a key symbol next to each column that is part of the primary key.
If you have a composite key the order is important when creating a FK, and sometimes the order is not how it is displayed.
What I do is go to the Keys section of the table1 and select script primary key as create to clipboard and then create FK using the order as shown in script
I've had this situation that led me to this topic. Same error but another cause. Maybe it will help someone.
Table1
ColA (PK)
ColB (PK)
ColC
Table2
ID (PK)
ColA
COLB
When trying to create foreign key in Table2 I've choose values from combobox in reverse order
Table1.ColB = Table2.ColB
Table1.ColA = Table2.ColA
This was throwing me an error like in topic name. Creating FK keeping order of columns in Primary key table as they are, made error disappear.
Stupid, but.. :)
If you still get that error after you have followed all advice from the above answers and everything looks right.
One way to fix it is by Removing your Primary keys for both tables, Save, Refresh, and add them again.
Then try to add your relationship again.
This Error happened with me When I tried to add foreign key constraint starting from PrimaryKey Table
Simpy go to other table and and create this foreign key constraint from there (foreign key Table)
This issue caught me out, I was adding the relationship on the wrong table. So if you're trying to add a relationship in table A to table B, try adding the relationship in table B to table A.
That looks like you are trying to create a foreign key in tblTwo that does not match (or participate) with any primary key or unique index in tblOne.
Check this link on MSDN regarding it. Here you have another link with a practical case.
EDIT:
Answwering to your comment, I understand you mean there are 2 fields in the primary key (which makes it a composite). In SQL it is not possible to have 2 primary keys on the same table.
IMHO, a foreign key field should always refer to a single register in the referenced table (i.e. the whole primary key in your case). That means you need to put both fields of the tblOne primary key in tblTwo before creating the foreign key.
Anyway, I have investigated a bit over the Internet and it seems SQL Server 2008 (as some prior versions and other RDBMS) gives you the possibility to reference only part of the primary key as long as this part is a candidate key (Not Null and Unique) and you create an unique constraint on it.
I am not sure you can use that in your case, but check this link for more information on it.
I have found that the column names must match.
Example:
So if tblOne has id called categoryId a reference in tblTwo must also be called categoryId.
_tblname, primary key name, foreign key_
tblOne, "categoryId", none
tblTwo, "exampleId", "categoryId"
I noticed this when trying to create foreign key between 2 tables that both had the column name "id" as primary key.
If nothing helps, then this could be the reason:
Considering this case:
Table A:
Column 1 (Primary Key)
Column 2 (Primary Key)
Column 3
Column 4
Table B:
Column a (Primary Key)
Column b
Column c
when you are defining a dependency B to A, then you are forced to respect the order in which the primaries are defined.
That's mean your dependency should look like this:
Table A Table B
Column 1 Column b
Column 2 Column c
AND NOT:
Table A Table B
Column 2 Column c
Column 1 Column b
then this will lead to the error you are encountering.
I've found another way to get this error. This can also happen if you are trying to make a recursive foreign key (a foreign key to the primary key in the same table) in design view in SQL Management Studio. If you haven't yet saved the table with the primary key it will return this message. Simply save the table then it will allow you to create the foreign key.
If you have data in your tables this could be the issue.
In my case I had some data in the Account table that I loaded at 3 pm, and some data in Contact table that I loaded at 3:10 pm, so Contact table had some values that weren't in my Account table yet.
I ended up deleting these values from the contact table and then managed to add a key without any problems.
Kindly also see that there are no existing data inside the table where the primary key is defined while setting the foreign key with another table column.
this was the cause of the error in my case.
I had to take backup empty the table set the relationship and then upload the data back.
sharing my experience
Was using ms sql smss
I'm learning databases, using SQLce. Got some problems, with this error:
A foreign key value cannot be inserted because a corresponding primary key value does not exist.
How does the integrity and acceptance of data work when attempting to save a data row that does not have specified one foreign key. Isn't it possible to set it to NULL in some way, meaning it will not reference the other table? In case, how would I do that? (For an integer key field)
Also, what if you save a row with a valid foreign key that corresponds to an existing primary key in other table. But then decide to delete that entry in this other table. So the foreign key will no longer be valid. Will I be allowed to delete? How does it work? I would think it should then be simply reset to a null value.. But maybe it's not that simple?
What you need to do is insert your data starting from the parent down.
So if you have an orders table and an items table that refers to orders, you have to create the new order first before adding all the children to the list.
Many of the data access libraries that you can get (in C# there is Linq to SQL) which will try and abstract this problem.
If you need to delete data you actually have to go the other way, delete the items before you delete the parent order record.
Of course, this assumes you are enforcing the foreign key, it is possible to not enforce the key, which might be useful during a bulk delete.
This is because of "bad data" you have in the tables. Check if you have all corresponding values in the primary table.
DBMS checks the referential integrity for ensuring the "correctness" of data within database.
For example, if you have a column called some_id in TableA with values 1 through 10 and a column called some_id in TableB with values 1 through 11 then TableA has no corresponding value (11) for that which you have already in TableB.
You can make a foreign key nullable but I don't recommend it. There are too many problems and inconsistencies that can arise. Redesign your tables so that you don't need to populate the foreign key for values that don't exist. Usually you can do that by moving the column to a new table for example.