I need to do updates over a table that contains over 600M lines on sql server, and this table does not contain the identity column, this is how it works by far :
UPDATE myTable set myBitColmun=1 where key='specifickey'
This kind of query takes over 1minute to update this specific line. And imagine the time needed to do updates on the whole table. And I need to do this kind of updates on my table everytime possible.
My question is : can identity column help perform update statement ?
alter table myTable
add id int identity(1,1)
and change my previous query:
UPDATE myTable set myBitColmun=1 where id=specificId
Related
I have a large table with given number of rows in which I'd like to replace personal informations with dummy data. I've written functions for this but actually struggling with how to implement it.
I'd like to do something like:
ALTER TABLE SomeTable DROP COLUMN SomeName
ALTER TABLE SomeTable ADD COLUMN SomeName NVARCHAR(30) DEFAULT (SELECT * FROM dbo.FakeName)
Help would be appreciated.
Instead of dropping and adding a column, just do an UPDATE.
If you just want to update the actual data with dummy data , why can't you use update statement as below. We do almost similar in our day to day work. For ex. if we would like to sanitize actual email address of users while restoring the data in my local or test machine (in column SomeName) and in another column we just want to update it with 'XXX' .
UPDATE SomeTable
SET Email_address= SUBSTRING(Email_address,0,CHARINDEX('#',Email_address)) + '#mytest.com',
SomeName2= 'XXX',
The primary key of my table is an Identity column of an ID. I want to be able to insert a new row and have it know what the last ID in the table currently is and add one to it. I know I can use Scope Identity to get the last inserted column from my code, but I am worried about people manually adding entries in the database, because they do this quite often. Is there a way I can look at the last ID in the table and not just the last ID my code inserted?
With a SQL Identity column, you don't need to do anything special. This is the default behavior. SQL Server will handle making sure you don't have collisions regardless of where the inserts come from.
The ##Identity will pull the latest identity, and scope_identity will grab the identity from the current scope.
A scope is a module: a stored procedure, trigger, function, or batch. Therefore, if two statements are in the same stored procedure, function, or batch, they are in the same scope.
If you don't want to allow manual entries to the primary column, then you can add Identity constraint to it along with primary key constraint.
Example, while creating a table,
CREATE Table t_Temp(RowID Int Primary Key Identity(1,1), Name Varchar(50))
INSERT Into t_Temp values ('UserName')
INSERT Into t_Temp values ('UserName1')
SELECT * from t_Temp
You can query the table and get the next available code in one SQL query:
SELECT COALESCE(MAX(CAST("RowID" AS INT)),0) +1 as 'NextRowID' from <tableName>
The "0" here is a default, meaning if there are no rows found, the first code returned would be (0+1) =1
Generally I have 999 instead of the 0 as I like my RowID/primary key etc. to start at 1000.
I want to add another row in my existing table and I'm a bit hesitant if I'm doing the right thing because it might skew the database. I have my script below and would like to hear your thoughts about it.
I want to add another row for 'Jane' in the table, which will be 'SKATING" in the ACT column.
Table: [Emp_table].[ACT].[LIST_EMP]
My script is:
INSERT INTO [Emp_table].[ACT].[LIST_EMP]
([ENTITY],[TYPE],[EMP_COD],[DATE],[LINE_NO],[ACT],[NAME])
VALUES
('REG','EMP','45233','2016-06-20 00:00:00:00','2','SKATING','JANE')
Will this do the trick?
Your statement looks ok. If the database has a problem with it (for example, due to a foreign key constraint violation), it will reject the statement.
If any of the fields in your table are numeric (and not varchar or char), just remove the quotes around the corresponding field. For example, if emp_cod and line_no are int, insert the following values instead:
('REG','EMP',45233,'2016-06-20 00:00:00:00',2,'SKATING','JANE')
Inserting records into a database has always been the most common reason why I've lost a lot of my hairs on my head!
SQL is great when it comes to SELECT or even UPDATEs but when it comes to INSERTs it's like someone from another planet came into the SQL standards commitee and managed to get their way of doing it implemented into the final SQL standard!
If your table does not have an automatic primary key that automatically gets generated on every insert, then you have to code it yourself to manage avoiding duplicates.
Start by writing a normal SELECT to see if the record(s) you're going to add don't already exist. But as Robert implied, your table may not have a primary key because it looks like a LOG table to me. So insert away!
If it does require to have a unique record everytime, then I strongly suggest you create a primary key for the table, either an auto generated one or a combination of your existing columns.
Assuming the first five combined columns make a unique key, this select will determine if your data you're inserting does not already exist...
SELECT COUNT(*) AS FoundRec FROM [Emp_table].[ACT].[LIST_EMP]
WHERE [ENTITY] = wsEntity AND [TYPE] = wsType AND [EMP_COD] = wsEmpCod AND [DATE] = wsDate AND [LINE_NO] = wsLineno
The wsXXX declarations, you will have to replace them with direct values or have them DECLAREd earlier in your script.
If you ran this alone and recieved a value of 1 or more, then the data exists already in your table, at least those 5 first columns. A true duplicate test will require you to test EVERY column in your table, but it should give you an idea.
In the INSERT, to do it all as one statement, you can do this ...
INSERT INTO [Emp_table].[ACT].[LIST_EMP]
([ENTITY],[TYPE],[EMP_COD],[DATE],[LINE_NO],[ACT],[NAME])
VALUES
('REG','EMP','45233','2016-06-20 00:00:00:00','2','SKATING','JANE')
WHERE (SELECT COUNT(*) AS FoundRec FROM [Emp_table].[ACT].[LIST_EMP]
WHERE [ENTITY] = wsEntity AND [TYPE] = wsType AND
[EMP_COD] = wsEmpCod AND [DATE] = wsDate AND
[LINE_NO] = wsLineno) = 0
Just replace the wsXXX variables with the values you want to insert.
I hope that made sense.
I am trying to add a column to a tsql table, i do this using SMO in c#. Altering the table is fine but i want to set the column to have a value. The table contains 650 million rows and the update query is taking over a day and a half to run.
Update [TempDatabase].[dbo].[table1] set RawSource = 'DTP'
This is the query I am running above.
Can anyone think of a more efficient way of doing this?
Thanks in advance.
Sometimes, it is more efficient to copy the table with the new value and re-create the table in a single command. Also, you might want to be sure that you have minimal logging for these operations.
Probably the best solution is to use a default value when you create the column:
alter table table1 add RawSource varchar(255) not null default 'DTP';
If you don't want the default moving forward, you can remove it after the column is added.
Another method uses computed columns, but basically does the same thing:
alter table table1 add _RawSource varchar(255);
alter table1 add RawSource as (coalesce(_RawSource, 'DTP'));
at the time of addition of column to table only we can set a default value which will applies for all rows
Note:U should keep not null compulsory because if not all rows are applicable with nulls
alter table table_name
add row_source nvarchar(5) not null default(N'DTP')
I have a column called fixedID, and it's current Value = 2, I want to update this value to be 42. What is the best way to do this. I would like to do this modification as simply as possible. However, if I could do this while doing an select insert that would be fantastic also.
update tblFixedId
set FixedId = (FixedId + 400)
possible to change the value here?
Select * INTO mynewTable from myOldertable
Identity columns are not updatable in SQL Server.
The only way of doing this as an actual UPDATE rather than a DELETE ... INSERT would be to use ALTER TABLE ... SWITCH to mark the column as no longer an IDENTITY column, do the UPDATE then ALTER TABLE ... SWITCH again to re-mark the column as IDENTITY (For example code the first way round see the workarounds on this Connect Item and for the second way here).
Note that in the common scenario that the identity column is the clustered index key the Update will likely be implemented as an INSERT ... DELETE anyway.