I am working on an assignment where I have to create a database using SQL Server 2019. I am wondering how to create a function which uses the existing PK of one table and puts it into the FK of the linked table. I can't upload a picture of it. But here is a description of my two tables:
Table Item:
Columns: itemID(PK), itemPackID(FK), description......
Table ItemPack:
Columns: ItemPackID(PK) ItemID(FK), quantity...
In the Item table, itemPackID as a foreign key is holding NULL and I want to replace the NULL with the PK value of the ItemPack table.
I'm considering that itemID(PK) is not null in ItemPack table. Please check the bellow code, hope this will help you.
SQL query:
UPDATE Item SET [itemPackID(FK)] = (SELECT [ItemPackID(PK)] FROM ItemPack WHERE [ItemID(FK)]=[itemID(PK)]) WHERE [itemPackID(FK)] IS NULL
Thank you
Related
I have created a database through Entity Framework Code First Approach and My application is ready and running live . The problem is that I did not turned "False" on Cascade Delete at the time of creating database.
Now if I delete any record from one table that is referenced with another table through foreign so all the record containing foreign key of deleted row is deleted from another table .
Practically demonstration :
Let say I have a Table called Passenger:
ID Name CategoryID
1 ABC 1
CategoryID here is a foreign key
Here is the category Table
ID Name
1 Gold
Let say I run my query on category table
delete from Category where ID = 1
Now all the record from my Passenger Table is deleted . I want to restrict it. Is it Possible through SQL now ?
I suppose
This is what you are looking for :
alter TRIGGER customers_del_prevent
ON dbo.customers
INSTEAD OF DELETE
AS
BEGIN
insert into dbo.log
values ('DELETE')
RAISERROR ('Deletions not allowed from this table (source = instead of)', 16, 1)
END
Hope this helps you. :)
I searched but only could found partial answer to this question
The goal would be here to create a new ID column on an existing table.
This new column would be the primary key for the table and I simply want it to be filled with integer values from 1 to number of rows.
What would be the query for that?
I know I have to first alter table to create the new column :
ALTER TABLE <MYTABLE> ADD (ID INTEGER);
Then I could use the series generator :
INSERT INTO <MYTABLE.ID> SELECT SERIES_GENERATE_INTEGER(1,1,(number of rows));
Once the column is filled I could use this line:
ALTER TABLE <MYTABLE> ADD PRIMARY KEY ("ID");
I am sure there is an easier way to do this
You wrote that you want to add a "new ID column to an existing table" and fill it with unique values.
That's not a "standard" operation in any DBMS, as the usual assumption is that records are created with a primary key and not retro fitted.
Thus, "ease" of operation for this is relative to what else you want to do.
For example, if you want to continue using this ID as a primary key for further operations, then using a once-off generator function like the SERIES_GENERATE_INTEGER or a query won't be very helpful since you have to avoid duplicates of already existing values.
Two, relatively easy, options come to mind:
Using a sequence:
create sequence myid;
update <table> set ID = myid.nextval;
And for succeeding inserts:
insert into <table> (id, ..., ...) VALUES (myid.nextval, ..., ...) ;
Note that this generates a value for every existing record and not a predefined set of size X.
Using a GUID
By using a GUID you generate a unique value every time you call the 'SYSUUID' function in SAP HANA. check docu here
Something like
update <table> set ID = SYSUUID;
should do the trick here.
Subsequent inserts would simply call the function for values of ID.
Application has different versions. Each version has it's own set of values in each table. I need to provide functionality to copy data from one version to another. Problem :
By inserting data I am trying to insert Ids which has already been in use in this table. So, I need to change ids of components which I want to insert but I must save relationship between those components. How cat I do that?
Create a master table which has a surrogate key as your primary key. A numeric value of type NUMBER(9) works well. You can create a sequence and trigger to automatically insert this.
The rest of the table is the column of your current table plus a column to indicate which version the row is for.
For simplicity you may wish to create views on top of the table along the lines of
select * from master_table where version_id = ####;
To copy the data from one version to another this will work:
Insert into master_table seq_master_table.nextval, new version_id,.....
from master_table
where version_id = ####;
I am trying to update a table so that rows that are missing are added and rows that are not up to date are updated using information from another table on a different database as a reference.
However, some tables have primary keys and some do not.
If there is a primary key the insert command will not run and if there is not a primary key, rows will duplicate.
Is there a way to have the insert command skip over primary key values that are already there?
I'm using sql server management studio 2005 and here is the code I have so far for a table with a primary key (PKcolumn):
INSERT [testDB].[dbo].[table1]
SELECT * FROM [sourceDB].[dbo].[table1]
UPDATE test
SET
test.[PKcolumn] = source.[PKcolumn]
,test.[column2] = source.[column2]
,test.[column3] = source.[column3]
FROM
[sourceDB].[dbo].[sourceDB] AS source
INNER JOIN
[testDB].[dbo].[PKcolumn] AS test
ON source.[PKcolumn] = test.[PKcolumn]
Update works perfectly but Insert will not run at all if there is even one duplicate.
Any suggestions on how to make this code work?
Also, any tips for doing the same thing on a table without a primary key?
You'll need to exclude rows that are already present in the table in your INSERT query, using a LEFT OUTER JOIN:
INSERT [testDB].[dbo].[table1]
SELECT * FROM [sourceDB].[dbo].[table1]
LEFT OUTER JOIN [testDB].[dbo].[table1] ON [sourceDB].[dbo].[table1].[PKcolumn] = [testDB].[dbo].[table1].[PKcolumn]
WHERE [testDB].[dbo].[table1].[PKcolumn] IS NULL
For a table without a primary key, I suppose you'd need to join on ALL columns to avoid duplicates.
I have the Tables
PatientEligibilit
and
PatientsEligibilitiesDoctorsSpecialties
and
DoctorsSpecialties
PatientEligibilit
has foreign key PatientsEligibilitiesDoctorsSpecialtyID from
PatientsEligibilitiesDoctorsSpecialties
table
and
PatientsEligibilitiesDoctorsSpecialty
has foreign key DoctorsSpecialtyID from
DoctorsSpecialties
table
THEN USING VB.NET LINQ: i'm tring to add child item ( PatientsEligibilitiesDoctorsSpecialty)
to it's parent (PatientEligibilit)
then I submit Changes
like :
PatientEligibilityObject.PatientsEligibilitiesDoctorsSpecialties.Add(New PatientsEligibilitiesDoctorsSpecialty With {.DoctorSpecialtyID = si.ID, .RegDate = Date.Now}) PatientEligibilityObject.PatientsEligibilitiesDoctorsSpecialties.Add(PEDS)
HMSData.SubmitChanges()
it's worked fine and save record in Database with correct date
BUT
DoctorSpecialtyID
always saved with value 1
I solve it. the problem was in the relation between the tables.
The foreign key between PatientEligibilit and PatientsEligibilitiesDoctorsSpecialties
was not correct..