I have a set of tables which track access logs. The logs contain data about the user's access including user agent strings. Since we know that user agent strings are, for all intents and purposes, practically unlimited, these would need to be stored as a text/blob type. Given the high degree of duplication, I'd like to store these in a separate reference table and have my main access log table have an id linking to it. Something like this:
accesslogs table:
username|accesstime|ipaddr|useragentid
useragents table:
id|crc32|md5|useragent
(the hashes are for indexing and quicker searching)
Here's the catch, i am working inside a framework that doesn't give me access to create fancy things like foreign keys. In addition, this has to be portable across multiple DBMSs. I have the join logic worked out for doing SELECTS but I am having trouble figuring out how to insert properly. I want to do something like
INSERT INTO accesslogs (username, accesstime, ipaddr, useragentid)
VALUES
(
:username,
:accesstime,
:ipaddr,
(
CASE WHEN
(
SELECT id
FROM useragents
WHERE
useragents.crc32 = :useragentcrc32
AND
useragents.md5 = :useragentmd5
AND useragents.useragent LIKE :useragent
) IS NOT NULL
THEN
THAT_SAME_SELECT_FROM_ABOVE()
ELSE
GET_INSERT_ID_FROM(INSERT INTO useragents (crc32, md5, useragent) VALUES (:useragentcrc32, :useragentmd5, :useragent))
)
)
Is there any way to do this that doesn't use pseudofunctions whose names i just made up? The two parts i'm missing is how to get the select from above and how to get the new id from a subquery insert.
You will need to do separate inserts to each of the tables. You can not do insert into both at the same time.
If you use MS SQL Server once you inserted you can get inserted id by SCOPE_IDENTITY(), and then use it in another table insert.
I'm not sure there is a cross platform way of doing this. You may have to have a lot of special cases for each supported back end. For Example, for SQL Server you'd use the merge statement as the basis of the solution. Other DBMSs have different names if they support it at all. Searching for "Upsert" might help.
Edt - added the second query to be explicit, and added parameters.
-- SQL Server Example
--Schema Defs
Create Table Test (
id int not null identity primary key,
UserAgent nvarchar(50)
)
Create Table WebLog (
UserName nvarchar(50),
APAddress nvarchar(50),
UserAgentID int
)
Create Unique Index UQ_UserAgent On Test(UserAgent)
-- Values parsed from log
Declare
#UserName nvarchar(50) = N'Loz',
#IPAddress nvarchar(50) = N'1.1.1.1',
#UserAgent nvarchar(50) = 'Test'
Declare #id int
-- Optionally Begin Transaction
-- Insert if necessary and get id
Merge
Into dbo.Test as t
Using
(Select #UserAgent as UserAgent) as s
On
t.[UserAgent] = s.[UserAgent]
When Matched Then
Update Set #id = t.id
When Not Matched Then
Insert (UserAgent) Values (s.UserAgent);
If #id Is Null Set #id = scope_identity()
Insert Into WebLog (UserName, IPAddress, UserAgentID) Values (#UserName, #IPAddress, #id)
-- Optionally Commit Transaction
Related
My database contains three tables called Object_Table, Data_Table and Link_Table. The link table just contains two columns, the identity of an object record and an identity of a data record.
I want to copy the data from DATA_TABLE where it is linked to one given object identity and insert corresponding records into Data_Table and Link_Table for a different given object identity.
I can do this by selecting into a table variable and the looping through doing two inserts for each iteration.
Is this the best way to do it?
Edit : I want to avoid a loop for two reason, the first is that I'm lazy and a loop/temp table requires more code, more code means more places to make a mistake and the second reason is a concern about performance.
I can copy all the data in one insert but how do get the link table to link to the new data records where each record has a new id?
In one statement: No.
In one transaction: Yes
BEGIN TRANSACTION
DECLARE #DataID int;
INSERT INTO DataTable (Column1 ...) VALUES (....);
SELECT #DataID = scope_identity();
INSERT INTO LinkTable VALUES (#ObjectID, #DataID);
COMMIT
The good news is that the above code is also guaranteed to be atomic, and can be sent to the server from a client application with one sql string in a single function call as if it were one statement. You could also apply a trigger to one table to get the effect of a single insert. However, it's ultimately still two statements and you probably don't want to run the trigger for every insert.
You still need two INSERT statements, but it sounds like you want to get the IDENTITY from the first insert and use it in the second, in which case, you might want to look into OUTPUT or OUTPUT INTO: http://msdn.microsoft.com/en-us/library/ms177564.aspx
The following sets up the situation I had, using table variables.
DECLARE #Object_Table TABLE
(
Id INT NOT NULL PRIMARY KEY
)
DECLARE #Link_Table TABLE
(
ObjectId INT NOT NULL,
DataId INT NOT NULL
)
DECLARE #Data_Table TABLE
(
Id INT NOT NULL Identity(1,1),
Data VARCHAR(50) NOT NULL
)
-- create two objects '1' and '2'
INSERT INTO #Object_Table (Id) VALUES (1)
INSERT INTO #Object_Table (Id) VALUES (2)
-- create some data
INSERT INTO #Data_Table (Data) VALUES ('Data One')
INSERT INTO #Data_Table (Data) VALUES ('Data Two')
-- link all data to first object
INSERT INTO #Link_Table (ObjectId, DataId)
SELECT Objects.Id, Data.Id
FROM #Object_Table AS Objects, #Data_Table AS Data
WHERE Objects.Id = 1
Thanks to another answer that pointed me towards the OUTPUT clause I can demonstrate a solution:
-- now I want to copy the data from from object 1 to object 2 without looping
INSERT INTO #Data_Table (Data)
OUTPUT 2, INSERTED.Id INTO #Link_Table (ObjectId, DataId)
SELECT Data.Data
FROM #Data_Table AS Data INNER JOIN #Link_Table AS Link ON Data.Id = Link.DataId
INNER JOIN #Object_Table AS Objects ON Link.ObjectId = Objects.Id
WHERE Objects.Id = 1
It turns out however that it is not that simple in real life because of the following error
the OUTPUT INTO clause cannot be on
either side of a (primary key, foreign
key) relationship
I can still OUTPUT INTO a temp table and then finish with normal insert. So I can avoid my loop but I cannot avoid the temp table.
I want to stress on using
SET XACT_ABORT ON;
for the MSSQL transaction with multiple sql statements.
See: https://msdn.microsoft.com/en-us/library/ms188792.aspx
They provide a very good example.
So, the final code should look like the following:
SET XACT_ABORT ON;
BEGIN TRANSACTION
DECLARE #DataID int;
INSERT INTO DataTable (Column1 ...) VALUES (....);
SELECT #DataID = scope_identity();
INSERT INTO LinkTable VALUES (#ObjectID, #DataID);
COMMIT
It sounds like the Link table captures the many:many relationship between the Object table and Data table.
My suggestion is to use a stored procedure to manage the transactions. When you want to insert to the Object or Data table perform your inserts, get the new IDs and insert them to the Link table.
This allows all of your logic to remain encapsulated in one easy to call sproc.
If you want the actions to be more or less atomic, I would make sure to wrap them in a transaction. That way you can be sure both happened or both didn't happen as needed.
You might create a View selecting the column names required by your insert statement, add an INSTEAD OF INSERT Trigger, and insert into this view.
Before being able to do a multitable insert in Oracle, you could use a trick involving an insert into a view that had an INSTEAD OF trigger defined on it to perform the inserts. Can this be done in SQL Server?
Insert can only operate on one table at a time. Multiple Inserts have to have multiple statements.
I don't know that you need to do the looping through a table variable - can't you just use a mass insert into one table, then the mass insert into the other?
By the way - I am guessing you mean copy the data from Object_Table; otherwise the question does not make sense.
//if you want to insert the same as first table
$qry = "INSERT INTO table (one, two, three) VALUES('$one','$two','$three')";
$result = #mysql_query($qry);
$qry2 = "INSERT INTO table2 (one,two, three) VVALUES('$one','$two','$three')";
$result = #mysql_query($qry2);
//or if you want to insert certain parts of table one
$qry = "INSERT INTO table (one, two, three) VALUES('$one','$two','$three')";
$result = #mysql_query($qry);
$qry2 = "INSERT INTO table2 (two) VALUES('$two')";
$result = #mysql_query($qry2);
//i know it looks too good to be right, but it works and you can keep adding query's just change the
"$qry"-number and number in #mysql_query($qry"")
I have 17 tables this has worked in.
-- ================================================
-- Template generated from Template Explorer using:
-- Create Procedure (New Menu).SQL
--
-- Use the Specify Values for Template Parameters
-- command (Ctrl-Shift-M) to fill in the parameter
-- values below.
--
-- This block of comments will not be included in
-- the definition of the procedure.
-- ================================================
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE InsetIntoTwoTable
(
#name nvarchar(50),
#Email nvarchar(50)
)
AS
BEGIN
SET NOCOUNT ON;
insert into dbo.info(name) values (#name)
insert into dbo.login(Email) values (#Email)
END
GO
I'm a novice when it comes to Stored Procedures in SQL Server Management Studio. I have an application that I was told to make the following changes to using a stored procedure:
Step 1. User types in an item number.
Step 2. Customer name, address, etc. displays in the other fields on the same form.
There are 3 tables: Bulk orders, Small orders, and Customer information.
Bulk orders and small orders are in Database_1 and Customer information is in Database_2.
The primary key for small orders is the order number. A column in small orders contains the customer number for each order. That customer number is the primary key in the customer table.
The bulk orders table is similar.
I want to include a conditional statement that says: if order number is found in small orders table, show data from customer table that coorelates with that order number. I've attempted this multiple ways, but keep getting a "The multi-part identifier.... could not be bound" error.
I.E:
SELECT DB1.db.Customer_Table.Customer_Column AS CustomerNumber;
IF(CustomerNumber NOT LIKE '%[a-z]%')
BEGIN
SELECT * FROM db.small_orders_table;
END
ELSE
BEGIN
SELECT * FROM db.buld_orders_table;
END
Please help.
Sounds like it's 2 databases on the same server...in that case, you'll need to specify the fully qualified table name (database.schema.table) when referencing a table on the other database from where your stored procedure is found.
Database_1.db.small_orders_tables
first of all, you cannot use aliases as variables. If you want to assign a value to a variable in order to test it, you have to do a SELECT statement like SELECT #var = DB1.db.Customer_Table.Customer_Column FROM <YourTableFullName> WHERE <condition>. Then you can use the #var (which must be declared before) for your test.
About the error you're experiencing, youre using fully qualified names in a wrong way. If you're on the same server (different databases), you need to specify just the database name on the top and then the schema of your objects. Suppose to have the following database objects on the Database1:
USE Database1;
GO
CREATE TABLE dbo.Table1
(
id int IDENTITY(1, 1) NOT NULL PRIMARY KEY CLUSTERED
, val varchar(30)
);
GO
INSERT INTO dbo.Table1 (val) VALUES ('test1');
GO
INSERT INTO dbo.Table1 (val) VALUES ('test2');
GO
INSERT INTO dbo.Table1 (val) VALUES ('test3');
GO
And the following ones on Database2:
USE Database2;
GO
CREATE TABLE dbo.Table2
(
id int IDENTITY(1, 1) NOT NULL PRIMARY KEY CLUSTERED
, val varchar(30)
);
GO
Now, suppose that you want to read from the first table the value with id = 2, and then to apply your IF. Let's declare a variable and test it:
USE Database1;
GO
DECLARE #var varchar(30);
-- since you're on Database1, you don't need to specify full name
SELECT #var = val FROM dbo.Table1 WHERE id = 2;
IF #var = 'test2'
BEGIN
SELECT id, val FROM dbo.Table1;
END
ELSE
BEGIN
-- in this case the database name is needed
SELECT id, val FROM Database2.dbo.Table2;
END
GO
Does it help?
This may have been asked before, but it's really hard to search for terms that limit the search results...
Take the following SQL snippet:
declare #source table (id int)
declare #target table(id int primary key, sourceId int)
set nocount on
insert into #target values (0,0)
insert into #source(id) values(1)
--insert into #source(id) values(2)
set nocount off
insert into #target select (select max(id)+1 from #target), s.id from #source s
select * from #target
This obviously executes without error, but now uncomment the second insert line and the following error occurs:
Msg 2627, Level 14, State 1, Line 15
Violation of PRIMARY KEY constraint 'PK__#7DB3CB72__7EA7EFAB'. Cannot insert duplicate key in object 'dbo.#target'.
I realise that the insert statement more than likely is effected against a snapshot of the #target table so (select max(id)+1 from #target) will always return a value of 1 - causing the violation error above...
Is there any way around this apart from resorting to a cursor?
Change your insert statement to the following:
insert into #target select (select
max(id) from #target) + (ROW_NUMBER()
OVER(ORDER BY s.id)), s.id from
#source s
This should work for this specific case but I would be careful about generalizing it.
You could use an identity column (that's exactly what they are meant for)
declare #target table(id int IDENTITY(1,1), sourceId int)
If your problem is that the select clause is "computed" before the insert is executed, there's afaik no way around this using a single SQL request
I think it's by design ; For your insertion to avoid duplicates, the index id must be computed during the insert, not during the select. This is the exact purpose of the IDENTITY keyword.
If you want to insert one select at a time, you must write separate requests (using cursors for example, but you'll lose atomicity, and will have to use proper locking keywords to avoid race conditions)
The way you're determining your new PK value, is a race condition waiting to happen.
If your DB is under high load, and multiple records are being inserted at the same time, you're going to get unexpected results.
Why don't you just use an identity column , and let the database handle the assignment of a new primary Id ?
Or, you can create some kind of meta-table, which holds a record for every table in your database, and this record contains the next value that should be used as a primary id in the table.
Then, you must make sure that every time you create a new record, you also update the next-value in your meta-table (and you should make sure that you do the appropriate locking), but, I see no added value in this approach vs making use of identity columns.
My database contains three tables called Object_Table, Data_Table and Link_Table. The link table just contains two columns, the identity of an object record and an identity of a data record.
I want to copy the data from DATA_TABLE where it is linked to one given object identity and insert corresponding records into Data_Table and Link_Table for a different given object identity.
I can do this by selecting into a table variable and the looping through doing two inserts for each iteration.
Is this the best way to do it?
Edit : I want to avoid a loop for two reason, the first is that I'm lazy and a loop/temp table requires more code, more code means more places to make a mistake and the second reason is a concern about performance.
I can copy all the data in one insert but how do get the link table to link to the new data records where each record has a new id?
In one statement: No.
In one transaction: Yes
BEGIN TRANSACTION
DECLARE #DataID int;
INSERT INTO DataTable (Column1 ...) VALUES (....);
SELECT #DataID = scope_identity();
INSERT INTO LinkTable VALUES (#ObjectID, #DataID);
COMMIT
The good news is that the above code is also guaranteed to be atomic, and can be sent to the server from a client application with one sql string in a single function call as if it were one statement. You could also apply a trigger to one table to get the effect of a single insert. However, it's ultimately still two statements and you probably don't want to run the trigger for every insert.
You still need two INSERT statements, but it sounds like you want to get the IDENTITY from the first insert and use it in the second, in which case, you might want to look into OUTPUT or OUTPUT INTO: http://msdn.microsoft.com/en-us/library/ms177564.aspx
The following sets up the situation I had, using table variables.
DECLARE #Object_Table TABLE
(
Id INT NOT NULL PRIMARY KEY
)
DECLARE #Link_Table TABLE
(
ObjectId INT NOT NULL,
DataId INT NOT NULL
)
DECLARE #Data_Table TABLE
(
Id INT NOT NULL Identity(1,1),
Data VARCHAR(50) NOT NULL
)
-- create two objects '1' and '2'
INSERT INTO #Object_Table (Id) VALUES (1)
INSERT INTO #Object_Table (Id) VALUES (2)
-- create some data
INSERT INTO #Data_Table (Data) VALUES ('Data One')
INSERT INTO #Data_Table (Data) VALUES ('Data Two')
-- link all data to first object
INSERT INTO #Link_Table (ObjectId, DataId)
SELECT Objects.Id, Data.Id
FROM #Object_Table AS Objects, #Data_Table AS Data
WHERE Objects.Id = 1
Thanks to another answer that pointed me towards the OUTPUT clause I can demonstrate a solution:
-- now I want to copy the data from from object 1 to object 2 without looping
INSERT INTO #Data_Table (Data)
OUTPUT 2, INSERTED.Id INTO #Link_Table (ObjectId, DataId)
SELECT Data.Data
FROM #Data_Table AS Data INNER JOIN #Link_Table AS Link ON Data.Id = Link.DataId
INNER JOIN #Object_Table AS Objects ON Link.ObjectId = Objects.Id
WHERE Objects.Id = 1
It turns out however that it is not that simple in real life because of the following error
the OUTPUT INTO clause cannot be on
either side of a (primary key, foreign
key) relationship
I can still OUTPUT INTO a temp table and then finish with normal insert. So I can avoid my loop but I cannot avoid the temp table.
I want to stress on using
SET XACT_ABORT ON;
for the MSSQL transaction with multiple sql statements.
See: https://msdn.microsoft.com/en-us/library/ms188792.aspx
They provide a very good example.
So, the final code should look like the following:
SET XACT_ABORT ON;
BEGIN TRANSACTION
DECLARE #DataID int;
INSERT INTO DataTable (Column1 ...) VALUES (....);
SELECT #DataID = scope_identity();
INSERT INTO LinkTable VALUES (#ObjectID, #DataID);
COMMIT
It sounds like the Link table captures the many:many relationship between the Object table and Data table.
My suggestion is to use a stored procedure to manage the transactions. When you want to insert to the Object or Data table perform your inserts, get the new IDs and insert them to the Link table.
This allows all of your logic to remain encapsulated in one easy to call sproc.
If you want the actions to be more or less atomic, I would make sure to wrap them in a transaction. That way you can be sure both happened or both didn't happen as needed.
You might create a View selecting the column names required by your insert statement, add an INSTEAD OF INSERT Trigger, and insert into this view.
Before being able to do a multitable insert in Oracle, you could use a trick involving an insert into a view that had an INSTEAD OF trigger defined on it to perform the inserts. Can this be done in SQL Server?
Insert can only operate on one table at a time. Multiple Inserts have to have multiple statements.
I don't know that you need to do the looping through a table variable - can't you just use a mass insert into one table, then the mass insert into the other?
By the way - I am guessing you mean copy the data from Object_Table; otherwise the question does not make sense.
//if you want to insert the same as first table
$qry = "INSERT INTO table (one, two, three) VALUES('$one','$two','$three')";
$result = #mysql_query($qry);
$qry2 = "INSERT INTO table2 (one,two, three) VVALUES('$one','$two','$three')";
$result = #mysql_query($qry2);
//or if you want to insert certain parts of table one
$qry = "INSERT INTO table (one, two, three) VALUES('$one','$two','$three')";
$result = #mysql_query($qry);
$qry2 = "INSERT INTO table2 (two) VALUES('$two')";
$result = #mysql_query($qry2);
//i know it looks too good to be right, but it works and you can keep adding query's just change the
"$qry"-number and number in #mysql_query($qry"")
I have 17 tables this has worked in.
-- ================================================
-- Template generated from Template Explorer using:
-- Create Procedure (New Menu).SQL
--
-- Use the Specify Values for Template Parameters
-- command (Ctrl-Shift-M) to fill in the parameter
-- values below.
--
-- This block of comments will not be included in
-- the definition of the procedure.
-- ================================================
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE InsetIntoTwoTable
(
#name nvarchar(50),
#Email nvarchar(50)
)
AS
BEGIN
SET NOCOUNT ON;
insert into dbo.info(name) values (#name)
insert into dbo.login(Email) values (#Email)
END
GO
How am I supposed to get the IDENTITY of an inserted row?
I know about ##IDENTITY and IDENT_CURRENT and SCOPE_IDENTITY, but don't understand the implications or impacts attached to each.
Can someone please explain the differences and when I would be using each?
##IDENTITY returns the last identity value generated for any table in the current session, across all scopes. You need to be careful here, since it's across scopes. You could get a value from a trigger, instead of your current statement.
SCOPE_IDENTITY() returns the last identity value generated for any table in the current session and the current scope. Generally what you want to use.
IDENT_CURRENT('tableName') returns the last identity value generated for a specific table in any session and any scope. This lets you specify which table you want the value from, in case the two above aren't quite what you need (very rare). Also, as #Guy Starbuck mentioned, "You could use this if you want to get the current IDENTITY value for a table that you have not inserted a record into."
The OUTPUT clause of the INSERT statement will let you access every row that was inserted via that statement. Since it's scoped to the specific statement, it's more straightforward than the other functions above. However, it's a little more verbose (you'll need to insert into a table variable/temp table and then query that) and it gives results even in an error scenario where the statement is rolled back. That said, if your query uses a parallel execution plan, this is the only guaranteed method for getting the identity (short of turning off parallelism). However, it is executed before triggers and cannot be used to return trigger-generated values.
I believe the safest and most accurate method of retrieving the inserted id would be using the output clause.
for example (taken from the following MSDN article)
USE AdventureWorks2008R2;
GO
DECLARE #MyTableVar table( NewScrapReasonID smallint,
Name varchar(50),
ModifiedDate datetime);
INSERT Production.ScrapReason
OUTPUT INSERTED.ScrapReasonID, INSERTED.Name, INSERTED.ModifiedDate
INTO #MyTableVar
VALUES (N'Operator error', GETDATE());
--Display the result set of the table variable.
SELECT NewScrapReasonID, Name, ModifiedDate FROM #MyTableVar;
--Display the result set of the table.
SELECT ScrapReasonID, Name, ModifiedDate
FROM Production.ScrapReason;
GO
I'm saying the same thing as the other guys, so everyone's correct, I'm just trying to make it more clear.
##IDENTITY returns the id of the last thing that was inserted by your client's connection to the database.
Most of the time this works fine, but sometimes a trigger will go and insert a new row that you don't know about, and you'll get the ID from this new row, instead of the one you want
SCOPE_IDENTITY() solves this problem. It returns the id of the last thing that you inserted in the SQL code you sent to the database. If triggers go and create extra rows, they won't cause the wrong value to get returned. Hooray
IDENT_CURRENT returns the last ID that was inserted by anyone. If some other app happens to insert another row at an unforunate time, you'll get the ID of that row instead of your one.
If you want to play it safe, always use SCOPE_IDENTITY(). If you stick with ##IDENTITY and someone decides to add a trigger later on, all your code will break.
The best (read: safest) way to get the identity of a newly-inserted row is by using the output clause:
create table TableWithIdentity
( IdentityColumnName int identity(1, 1) not null primary key,
... )
-- type of this table's column must match the type of the
-- identity column of the table you'll be inserting into
declare #IdentityOutput table ( ID int )
insert TableWithIdentity
( ... )
output inserted.IdentityColumnName into #IdentityOutput
values
( ... )
select #IdentityValue = (select ID from #IdentityOutput)
Add
SELECT CAST(scope_identity() AS int);
to the end of your insert sql statement, then
NewId = command.ExecuteScalar()
will retrieve it.
From MSDN
##IDENTITY, SCOPE_IDENTITY, and IDENT_CURRENT are similar functions in that they return the last value inserted into the IDENTITY column of a table.
##IDENTITY and SCOPE_IDENTITY will return the last identity value generated in any table in the current session. However, SCOPE_IDENTITY returns the value only within the current scope; ##IDENTITY is not limited to a specific scope.
IDENT_CURRENT is not limited by scope and session; it is limited to a specified table. IDENT_CURRENT returns the identity value generated for a specific table in any session and any scope. For more information, see IDENT_CURRENT.
IDENT_CURRENT is a function which takes a table as a argument.
##IDENTITY may return confusing result when you have an trigger on the table
SCOPE_IDENTITY is your hero most of the time.
When you use Entity Framework, it internally uses the OUTPUT technique to return the newly inserted ID value
DECLARE #generated_keys table([Id] uniqueidentifier)
INSERT INTO TurboEncabulators(StatorSlots)
OUTPUT inserted.TurboEncabulatorID INTO #generated_keys
VALUES('Malleable logarithmic casing');
SELECT t.[TurboEncabulatorID ]
FROM #generated_keys AS g
JOIN dbo.TurboEncabulators AS t
ON g.Id = t.TurboEncabulatorID
WHERE ##ROWCOUNT > 0
The output results are stored in a temporary table variable, joined back to the table, and return the row value out of the table.
Note: I have no idea why EF would inner join the ephemeral table back to the real table (under what circumstances would the two not match).
But that's what EF does.
This technique (OUTPUT) is only available on SQL Server 2008 or newer.
Edit - The reason for the join
The reason that Entity Framework joins back to the original table, rather than simply use the OUTPUT values is because EF also uses this technique to get the rowversion of a newly inserted row.
You can use optimistic concurrency in your entity framework models by using the Timestamp attribute: 🕗
public class TurboEncabulator
{
public String StatorSlots)
[Timestamp]
public byte[] RowVersion { get; set; }
}
When you do this, Entity Framework will need the rowversion of the newly inserted row:
DECLARE #generated_keys table([Id] uniqueidentifier)
INSERT INTO TurboEncabulators(StatorSlots)
OUTPUT inserted.TurboEncabulatorID INTO #generated_keys
VALUES('Malleable logarithmic casing');
SELECT t.[TurboEncabulatorID], t.[RowVersion]
FROM #generated_keys AS g
JOIN dbo.TurboEncabulators AS t
ON g.Id = t.TurboEncabulatorID
WHERE ##ROWCOUNT > 0
And in order to retrieve this Timetsamp you cannot use an OUTPUT clause.
That's because if there's a trigger on the table, any Timestamp you OUTPUT will be wrong:
Initial insert. Timestamp: 1
OUTPUT clause outputs timestamp: 1
trigger modifies row. Timestamp: 2
The returned timestamp will never be correct if you have a trigger on the table. So you must use a separate SELECT.
And even if you were willing to suffer the incorrect rowversion, the other reason to perform a separate SELECT is that you cannot OUTPUT a rowversion into a table variable:
DECLARE #generated_keys table([Id] uniqueidentifier, [Rowversion] timestamp)
INSERT INTO TurboEncabulators(StatorSlots)
OUTPUT inserted.TurboEncabulatorID, inserted.Rowversion INTO #generated_keys
VALUES('Malleable logarithmic casing');
The third reason to do it is for symmetry. When performing an UPDATE on a table with a trigger, you cannot use an OUTPUT clause. Trying do UPDATE with an OUTPUT is not supported, and will give an error:
Cannot use UPDATE with OUTPUT clause when a trigger is on the table
The only way to do it is with a follow-up SELECT statement:
UPDATE TurboEncabulators
SET StatorSlots = 'Lotus-O deltoid type'
WHERE ((TurboEncabulatorID = 1) AND (RowVersion = 792))
SELECT RowVersion
FROM TurboEncabulators
WHERE ##ROWCOUNT > 0 AND TurboEncabulatorID = 1
I can't speak to other versions of SQL Server, but in 2012, outputting directly works just fine. You don't need to bother with a temporary table.
INSERT INTO MyTable
OUTPUT INSERTED.ID
VALUES (...)
By the way, this technique also works when inserting multiple rows.
INSERT INTO MyTable
OUTPUT INSERTED.ID
VALUES
(...),
(...),
(...)
Output
ID
2
3
4
##IDENTITY is the last identity inserted using the current SQL Connection. This is a good value to return from an insert stored procedure, where you just need the identity inserted for your new record, and don't care if more rows were added afterward.
SCOPE_IDENTITY is the last identity inserted using the current SQL Connection, and in the current scope -- that is, if there was a second IDENTITY inserted based on a trigger after your insert, it would not be reflected in SCOPE_IDENTITY, only the insert you performed. Frankly, I have never had a reason to use this.
IDENT_CURRENT(tablename) is the last identity inserted regardless of connection or scope. You could use this if you want to get the current IDENTITY value for a table that you have not inserted a record into.
ALWAYS use scope_identity(), there's NEVER a need for anything else.
One other way to guarantee the identity of the rows you insert is to specify the identity values and use the SET IDENTITY_INSERT ON and then OFF. This guarantees you know exactly what the identity values are! As long as the values are not in use then you can insert these values into the identity column.
CREATE TABLE #foo
(
fooid INT IDENTITY NOT NULL,
fooname VARCHAR(20)
)
SELECT ##Identity AS [##Identity],
Scope_identity() AS [SCOPE_IDENTITY()],
Ident_current('#Foo') AS [IDENT_CURRENT]
SET IDENTITY_INSERT #foo ON
INSERT INTO #foo
(fooid,
fooname)
VALUES (1,
'one'),
(2,
'Two')
SET IDENTITY_INSERT #foo OFF
SELECT ##Identity AS [##Identity],
Scope_identity() AS [SCOPE_IDENTITY()],
Ident_current('#Foo') AS [IDENT_CURRENT]
INSERT INTO #foo
(fooname)
VALUES ('Three')
SELECT ##Identity AS [##Identity],
Scope_identity() AS [SCOPE_IDENTITY()],
Ident_current('#Foo') AS [IDENT_CURRENT]
-- YOU CAN INSERT
SET IDENTITY_INSERT #foo ON
INSERT INTO #foo
(fooid,
fooname)
VALUES (10,
'Ten'),
(11,
'Eleven')
SET IDENTITY_INSERT #foo OFF
SELECT ##Identity AS [##Identity],
Scope_identity() AS [SCOPE_IDENTITY()],
Ident_current('#Foo') AS [IDENT_CURRENT]
SELECT *
FROM #foo
This can be a very useful technique if you are loading data from another source or merging data from two databases etc.
Create a uuid and also insert it to a column. Then you can easily identify your row with the uuid. Thats the only 100% working solution you can implement. All the other solutions are too complicated or are not working in same edge cases.
E.g.:
1) Create row
INSERT INTO table (uuid, name, street, zip)
VALUES ('2f802845-447b-4caa-8783-2086a0a8d437', 'Peter', 'Mainstreet 7', '88888');
2) Get created row
SELECT * FROM table WHERE uuid='2f802845-447b-4caa-8783-2086a0a8d437';
Even though this is an older thread, there is a newer way to do this which avoids some of the pitfalls of the IDENTITY column in older versions of SQL Server, like gaps in the identity values after server reboots. Sequences are available in SQL Server 2016 and forward which is the newer way is to create a SEQUENCE object using TSQL. This allows you create your own numeric sequence object in SQL Server and control how it increments.
Here is an example:
CREATE SEQUENCE CountBy1
START WITH 1
INCREMENT BY 1 ;
GO
Then in TSQL you would do the following to get the next sequence ID:
SELECT NEXT VALUE FOR CountBy1 AS SequenceID
GO
Here are the links to CREATE SEQUENCE and NEXT VALUE FOR
Complete solution in SQL and ADO.NET
const string sql = "INSERT INTO [Table1] (...) OUTPUT INSERTED.Id VALUES (...)";
using var command = connection.CreateCommand();
command.CommandText = sql;
var outputIdParameter = new SqlParameter("#Id", SqlDbType.Int) { Direction = ParameterDirection.Output };
command.Parameters.Add(outputIdParameter);
await connection.OpenAsync();
var outputId= await command.ExecuteScalarAsync();
await connection.CloseAsync();
int id = Convert.ToInt32(outputId);
After Your Insert Statement you need to add this. And Make sure about the table name where data is inserting.You will get current row no where row affected just now by your insert statement.
IDENT_CURRENT('tableName')