I'm creating a table to store cars, and another table to store the time when the new car was added to the database, can someone please explain to me how to create the relationship to update time automatically when the car was created.
Create table Cars
(
CarID int Primary Key identity(1,1),
Make varchar(50),
Model varchar(50),
Colour varchar(59)
)
create Table TimeLogs
(
AddedOn SYSDATETIME(),
CarId int unique foreign key references Cars(CarId)
)
I would solve this by not using a second table for what should be a column in the Cars table. The table would be designed more appropriately like this.
Create table Cars
(
CarID int Primary Key identity(1,1),
Make varchar(50),
Model varchar(50),
Colour varchar(59),
AddedOn datetime default SYSDATETIME()
)
To automatically update one table whenever another table is updated, you need to use a TRIGGER.
You needs to use insert trigger for the same, as below
CREATE TRIGGER yourNewTrigger ON yourSourcetable
FOR INSERT
AS
INSERT INTO yourDestinationTable
(col1, col2 , col3, user_id, user_name)
SELECT
'a' , default , null, user_id, user_name
FROM inserted
go
Related
How can I clone a table with guid's as well as another table that references those guid's as foreign keys.
The two tables have a one to many relationship. I would need to do this in an automated way.
My problem is being able to reference the relationship between the two tables when newly created guid's are created during the clone.
EDIT: I need to clone the entries to the tables themselves, not new tables.
Basically, we want to duplicate the Tables with new Ids but keep the relationship the same as the originals.
If required, you could keep the same Ids, but in practice this shouldn't be a requirement; for testing, the Ids should not matter - only the relationship.
I'll demonstrate this with two Tables:
The first is AnimalType with Id (uniqueidentifier - RowGuid, Primary Key) and AnimalType (nvarchar) Columns
The second is Animal with AnimalName (nvarchar) and AnimalType (uniqueidentifier, Foreign Key) Columns
For the parent/lookup Table:
Create a new Table (newTable) to populate with the data of the existing Table (oldTable).
Create newTable with its own Primary Key Id column (ROWGUID, IDENTITY etc.) with its Default
Create an extra Column in newTable to hold a copy of oldTable's Id Column values
The Id Column in newTable will generate unique Ids on creation of records
The second (child) Table:
Create a new Table (newChildTable) to populate with the data of the existing Table (oldChildTable).
Create newChildTable with its own Foreign Key Column to point to newTable's Primary Key Column
Create an extra Column in newChildTable to hold a copy of oldChildTable's Foreign Key Column values
Once created, we populate the new parent/lookup Table with the data from the original Table, placing the Id values in the extra Column added for this data. The Table's own Ids will generate uniquely as usual.
Next, we populate the child Table with the data from its original Table, placing the original Foreign Key Column values into the added Column for this data.
Next, we join the two new tables on the Columns that hold the original Id values and update the Foreign Key Column values to the new Ids in the parent/lookup Table.
Finally, we can remove the Columns holding the original Id values, and we are left with two Tables linked to the same data but by the new Ids we generated when created when the records were copied.
You will not have any reference to the original Ids - just in case of selecting the wrong Table at any time in your testing (although this should be done in a different server...). If you needed the original Ids too, you can perform the above, not move the Ids around, rename the Columns etc. - as you wish really.
/*
Create copy of parent/lookup Table with its own Id column
Add a column to hold the original Ids
*/
CREATE TABLE [dbo].[AnimalTypeBak](
[Id] [uniqueidentifier] ROWGUIDCOL NOT NULL CONSTRAINT [DF_AnimalTypeBak_Id] DEFAULT (newid()),
[OriginalId] [uniqueidentifier] NOT NULL,
[AnimalType] [nvarchar](32) NOT NULL,
CONSTRAINT [PK_AnimalTypeBak] PRIMARY KEY CLUSTERED
(
[Id] ASC
)
) ON [PRIMARY]
GO
/*
Create copy of child Table
Add a column to hold the original Foreign Key values
*/
CREATE TABLE [dbo].[AnimalBak](
[AnimalName] [nvarchar](20) NOT NULL,
[OriginalAnimalType] [uniqueidentifier] NOT NULL,
[AnimalType] [uniqueidentifier] NOT NULL
) ON [PRIMARY]
GO
/*
Import data from the parent/lookup Table placing the origional Ids into the added Column
*/
INSERT INTO [dbo].[AnimalTypeBak]
([OriginalId]
,[AnimalType])
SELECT [Id], [AnimalType]
FROM [dbo].[AnimalType]
GO
/*
Import data from the child Table placing the origional Foreign Key values into the added Column
*/
INSERT INTO [dbo].[AnimalBak]
([OriginalAnimalType]
,[AnimalName])
SELECT [AnimalType], [AnimalName]
FROM [dbo].[Animal]
GO
/*
Update the child Table placing the new parent/lookup Ids into the Foreign Key Column
*/
UPDATE [dbo].[AnimalBak]
SET [dbo].[AnimalBak].[AnimalType] = [dbo].[AnimalTypeBak].[Id]
FROM [dbo].[AnimalBak]
INNER JOIN [dbo].[AnimalTypeBak]
ON [dbo].[AnimalBak].[OriginalAnimalType] = [dbo].[AnimalTypeBak].[OriginalId]
GO
/*
Drop the redundant Columns
*/
ALTER TABLE [dbo].[AnimalBak]
DROP COLUMN [OriginalAnimalType]
GO
ALTER TABLE [dbo].[AnimalTypeBak]
DROP COLUMN [OriginalId]
/*
Add the Foreign Key Contraint between the two Tables
*/
ALTER TABLE [dbo].[AnimalBak] WITH CHECK ADD CONSTRAINT [FK_AnimalBak_AnimalTypeBak] FOREIGN KEY([AnimalType])
REFERENCES [dbo].[AnimalTypeBak] ([Id])
GO
/*
And select the data to ensure the data is related as it was in the original Tables
*/
SELECT a.AnimalName, a.AnimalType, b.AnimalType FROM [dbo].[AnimalBak] as a INNER JOIN [dbo].[AnimalTypeBak] as b ON b.Id = a.AnimalType
declare #Parents table (Id uniqueidentifier, Name varchar(50));
declare #Children table (Id uniqueidentifier, ParentId uniqueidentifier, Name varchar(50));
declare #NewId uniqueidentifier = newid();
insert into #Parents values (#NewId, 'Original parent');
insert into #Children values (newid(), #NewId, 'First original child');
insert into #Children values (newid(), #NewId, 'Second original child');
declare #Ids table (CloneId uniqueidentifier, OriginalId uniqueidentifier);
merge #Parents as target
using (
select
CloneId = newid(),
OriginalId = Id,
Name = Name + ' (Cloned)'
from
#Parents
where
Id = #NewId
)
as source on source.CloneId = target.Id
when not matched by target then
insert (Id, Name)
values (source.CloneId, source.Name)
output
source.CloneId, source.OriginalId
into #Ids (CloneId, OriginalId);
merge #Children as target
using (
select
Id = newid(),
ParentId = ids.CloneId,
Name = Name + ' (Cloned)'
from
#Children c
inner join #Ids ids on ids.OriginalId = c.ParentId
)
as source on source.Id = target.Id
when not matched by target then
insert (Id, ParentId, Name)
values (source.Id, source.ParentId, source.Name);
select * from #Parents
select * from #Children
CREATE TABLE Persons
(
P_Id varchar(6) NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
PRIMARY KEY (P_Id)
)
in this table P_Id is the primary key. We want to generate autoincrement of P_Id with default value (PN00) in the start while inserting only LastName and FirstName .eg :-PN001 for first entry ,PN002 for second,PN003 for third and so on .
The only viable solution is to use
an ID INT IDENTITY(1,1) column to get SQL Server to handle the automatic increment of your numeric value
a computed, persisted column to convert that numeric value to the value you need
So try this:
CREATE TABLE dbo.Persons
(ID INT IDENTITY(1,1) NOT NULL PRIMARY KEY CLUSTERED,
P_ID AS 'PN' + RIGHT('00000' + CAST(ID AS VARCHAR(5)), 5) PERSISTED,
.... your other columns here....
)
Now, every time you insert a row into Persons without specifying values for ID or P_ID:
INSERT INTO dbo.Persons(Col1, Col2, ..., ColN)
VALUES (Val1, Val2, ....., ValN)
then SQL Server will automatically and safely increase your ID value, and P_Id will contain values like PN00001, PN00002,...... and so on - automatically, safely, reliably, no duplicates.
There are different ways to address your issue.
You could use a Trigger.Triggers are activated on some events. You could create a trigger for 'Instead of Insert On Persons' event. When the event is triggered, then generate a new P_Id. Insert this new P_Id alongwith all the values as the new record for your table.
This approach wont have coupling with the table's schema.
Refer this link for more information on Triggers :
https://msdn.microsoft.com/en-IN/library/ms189799.aspx
Refer this link to emulate 'before insert trigger' in SQL Server:
How to emulate a BEFORE INSERT trigger in T-SQL / SQL Server for super/subtype (Inheritence) entities?
You could also use a Procedure like :
create procedure Persons_insert(#lastname varchar(255), #firstname varchar(255))
as
begin
--write code to generate the ID as you like
insert into Persons(p_id,lastname,firstname)values(generated_id,lastname,firstname);
end
I have created two tables and also created a relationship between them.
Table students:
create table students
(
[StudentId] NVARCHAR(50) NOT NULL PRIMARY KEY,
[Name] NVARCHAR(50) NOT NULL
);
Table studentprofile:
create table studentprofile
(
[Id] INT NOT NULL PRIMARY KEY IDENTITY(1, 1),
[StudentId] NVARCHAR(50) NOT NULL,
[Address] NVARCHAR(50) NOT NULL,
);
and relationship:
alter table studentprofile
add constraint students_studentprofile_FK
foreign key (StudentId)
references students(StudentId)
on delete cascade on update cascade
But, when I wrote this line:
insert into students values('110111', 'Marik')
the value of StudentId (in table studentprofile) wasn't updated automatically. Why?
Can you tell me how to set the value of StudentId (in table studentprofile) can be inserted automatically whenever I insert into table students?
There is no such thing as insert cascade.
You can implement such a thing by using a trigger for insert on your students table, inserting default values (or nulls) into the studentprofile table:
CREATE TRIGGER students_insert ON students AFTER INSERT
AS
INSERT INTO studentprofile(StudentId, Address)
SELECT StudentId, 'NO ADDRESS'
FROM inserted
Note that your Address column is defined as not null and has no default value, this is why I've used the hard coded 'NO ADDRESS' for it.
However, I agree with the comments on your question: you would be better off inserting the data to the student profile using a different insert statement (perhaps inside a transaction with the insert to students).
I am aware that using IDENT_CURRENT will not always return me the correct identity value (especially true in multi-threaded applications). I wanted to use SCOPE_IDENTITY() instead.
For example this is my Employee table:
create table Employee
(
ID int identity(1,1),
Name varchar(20),
SystemID int,
constraint Employee_PK primary key (ID asc)
)
I have a statement below:
alter table Employee
add constraint Employee_D1 default ident_current('Employee') for SystemID
which I need to modify to use SCOPE_IDENTITY() instead.
I tried the below:
alter table Employee
add constraint Employee_D1 default SCOPE_IDENITITY() for SystemID
This did not give any errors. But upon inserting a row, I did not see this column getting updated with the identity value. What am I doing wrong?
Note that the SystemID must not be readonly, so computed field isn't an option.
My exercise here is to try eliminating entry of wrong IDENTITY value in SystemID in case parallel processes try to insert rows.
Just re-read your answer. SystemID isn't an identity column. I don't think you can use SCOPE_IDENITITY() as it hasn't added the row and retrieved the new Identity value at the point it would need the value to save.
What you will need to do is create a trigger After Insert of the row to update the SystemId value. CREATE TRIGGER
Here's how I'd approach this problem (apologies for the poor field names, I'm not feeling inventive)
CREATE TABLE employees (
id int identity(1,1) NOT NULL
, name varchar(20) NOT NULL
, actual_system_id int NULL
, system_id As Coalesce(actual_system_id, id)
, CONSTRAINT pk_employees PRIMARY KEY (id)
)
;
INSERT INTO employees (name)
VALUES ('John')
, ('Paul')
, ('George')
, ('Ringo')
;
SELECT id
, name
, system_id
FROM employees
;
UPDATE employees
SET actual_system_id = 937
WHERE name = 'George'
;
SELECT id
, name
, system_id
FROM employees
;
Yes i am very well aware the consequences. But i just want to reorder them. Start from 1 to end.
How do I go about reordering the keys using a single query ?
It is clustered primary key index
Reordering like
First record Id 1
second record Id 2
The primary key is Int
Drop PK constraint
Drop Identity column
Re-create Identity Column
Re-Create PK
USE Test
go
if(object_id('IdentityTest') Is not null)
drop table IdentityTest
create table IdentityTest
(
Id int identity not null,
Name varchar(5),
constraint pk primary key (Id)
)
set identity_insert dbo.IdentityTest ON
insert into dbo.IdentityTest (Id,Name) Values(23,'A'),(26,'B'),(34,'C'),(35,'D'),(40,'E')
set identity_insert dbo.IdentityTest OFF
select * from IdentityTest
------------------1. Drop PK constraint ------------------------------------
ALTER TABLE [dbo].[IdentityTest] DROP CONSTRAINT [pk]
GO
------------------2. Drop Identity column -----------------------------------
ALTER table dbo.IdentityTest
drop column Id
------------------3. Re-create Identity Column -----------------------------------
ALTER table dbo.IdentityTest
add Id int identity(1,1)
-------------------4. Re-Create PK-----------------------
ALTER TABLE [dbo].[IdentityTest] ADD CONSTRAINT [pk] PRIMARY KEY CLUSTERED
(
[Id] ASC
)
--------------------------------------------------------------
insert into dbo.IdentityTest (Name) Values('F')
select * from IdentityTest
IDENTITY columns are not updatable irrespective of SET IDENTITY_INSERT options.
You could create a shadow table with the same definition as the original except for the IDENTITY property. Switch into that (this is a metadata only change with no movement of rows that just affects the table's definition) then update the rows and switch back though.
A full worked example going from a situation with gaps to no gaps is shown below (error handling and transactions are omitted below for brevity).
Demo Scenario
/*Your original table*/
CREATE TABLE YourTable
(
Id INT IDENTITY PRIMARY KEY,
OtherColumns CHAR(100) NULL
)
/*Some dummy data*/
INSERT INTO YourTable (OtherColumns) VALUES ('A'),('B'),('C')
/*Delete a row leaving a gap*/
DELETE FROM YourTable WHERE Id =2
/*Verify there is a gap*/
SELECT *
FROM YourTable
Remove Gaps
/*Create table with same definition as original but no `IDENTITY`*/
CREATE TABLE ShadowTable
(
Id INT PRIMARY KEY,
OtherColumns CHAR(100)
)
/*1st metadata switch*/
ALTER TABLE YourTable SWITCH TO ShadowTable;
/*Do the update*/
WITH CTE AS
(
SELECT *,
ROW_NUMBER() OVER (ORDER BY Id) AS RN
FROM ShadowTable
)
UPDATE CTE SET Id = RN
/*Metadata switch back to restore IDENTITY property*/
ALTER TABLE ShadowTable SWITCH TO YourTable;
/*Remove unneeded table*/
DROP TABLE ShadowTable;
/*No Gaps*/
SELECT *
FROM YourTable
I don't think there is any way to do this in a single query. Your best bet is to copy the data to a new table, drop and recreate the original table (or delete the data and reseed the identity) and reinsert the data in the original order using the previous identity as the ordering (but not re-inserting it).
CREATE TABLE Table1_Stg (bla bla bla)
INSERT INTO Table1_Stg (Column2, Column3,...) SELECT Column2, Column3,... FROM Table1 ORDER BY Id
Here the Id column is excluded from the SELECT column list.
Or, you can do:
SELECT * INTO Table1_Stg FROM Table1 ORDER BY Id
DROP Table1
sp_rename Table1_stg Table1
Please lookup the usage for sp_rename as I am doing this from memory.
Hope this helps.
EDIT: Please save a script with all your indexes and constraints if any on Table1.
EDIT2: Added second method of creating table and inserting into table.
UPDATE tbl SET id = (SELECT COUNT(*) FROM tbl t WHERE t.id <= tbl.id);
This last statement is genius. Just had to remove the primary key from the table design first and make sure under the design option Identity Specifications is set to no. Once you run the query set these options back.