I am relatively new to databases and SQL, and I am not clear on how or whether transactions may relate to a problem that I am trying to solve. I want to be able to temporarily set a value in a database table, run some query, and then clear out the value that was set, and I don't want any operations outside of the transaction to be able to see or alter the temporary value that was set.
The reason I am doing this is so that I can create predefined views that query certain data depending on variables such as the current user's id. In order for the predefined view to have access to the current user's id, I would save the id into a special table just before querying the view, then delete the id immediately afterward. I don't want to worry about some other user overwriting the current user's id while the transaction is in process. Is this a proper use for a transaction?
I am using H2 if that makes a difference.
SET #tempVar=value;
I don't know if you really need to go through the pain of creating a temp table and setting the value. This seems far simpler.
You can then do - SELECT * FROM TABLE_NAME WHERE COLUMN=#tempVar;
I think you want a Procedure or Function. Both can take a parameter as input.
ex.
CREATE PROCEDURE pr_emp
(
#input INT
)
AS
SELECT *
FROM myTable
WHERE emp_id = #input
ex.
CREATE FUNCTION v_empid (#input INT)
RETURNS TABLE
AS
RETURN
SELECT * FROM myTABLE WHERE emp_id = #input;
These could let you to access information for an empid. For example:
SELECT * FROM v_empid(32)
Related
I'm trying to split what was a large table update into multiple inserts into working tables. One of the queries needs uses the row number in it. On an INSERT in oracle, can I explicitly add the ROWNUM as an explicit column? This is a working table ultimately used in a reporting operation with a nasty partion over clause and having a true row number is helpful.
create table MY_TABLE(KEY number,SOMEVAL varchar2(30),EXPLICIT_ROW_NUMBER NUMBER);
INSERT /*+PARALLEL(AUTO) */ INTO MY_TABLE(KEY,SOMEVAL,EXPLICIT_ROW_NUMBER) (
SELECT /*+PARALLEL(AUTO) */ KEY,SOMEVAL,ROWNUM
FROM PREVIOUS_VERSION_OF_MY_TABLE
);
where PREVIOUS_VERSION_OF_MY_TABLE has both a KEY and SOMEVAL fields.
I'd like it to number the rows in the order that the inner select statement does it. So, the first row in the select, had it been explicitly run, would have a ROWNUM of 1, etc. I don't want it reversed, etc.
The table above has over 80MM records. Originally I used an UPDATE, and when I ran it, I got some ORA error saying that I ran out of UNDO space. I do not have the exact error message at this point anymore.
I'm trying to accomplish the same thing with multiple working tables that I would have done with one or more updates. Apparently it is either hard, impossible, etc to add UNDO space, for this query (our company DB team says), without making me a DBA, or spending about $100 on a hard drive and attaching it to the instance. So I need to write a harder query to get around this limitation. The goal is to have a session id and timestamps within that session, but for each timestamp within a session (except the last timestamp), show the next session. The original query is included below:
update sc_hub_session_activity schat
set session_time_stamp_rank = (
select /*+parallel(AUTO) */ order_number
from (
select /*+parallel(AUTO) */ schat_all.explicit_row_number as explicit_row_number,row_number() over (partition by schat_all.session_key order by schat_all.session_key,schat_all.time_stamp) as order_number
from sc_hub_session_activity schat_all
where schat_all.session_key=schat.session_key
) schat_all_group
where schat.explicit_row_number = schat_all_group.explicit_row_number
);
commit;
update sc_hub_session_activity schat
set session_next_time_stamp = (
select /*+parallel(AUTO) */ time_stamp
from sc_hub_session_activity schat2
where (schat2.session_time_stamp_rank = schat.session_time_stamp_rank+1) and (schat2.session_key = schat.session_key)
);
commit;
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',
I'm trying to figure out how to determine if a table has been affected by a number of processes that run in sequence, and need to know what the state of the table is before and after each runs. What I've been trying to do is run some SQL before all the processes run that saves a before checksum of every table in the db to a table, then running it again when each ends and updating the table row with an after checksum. After all the processes are over, I compare the checksums and get all rows where before <> after.
Only problem is that I'm not the best guy for SQL, and am a little lost. Here's where I'm at right now:
select checksum_agg(binary_checksum(*)) from empcomp with (nolock)
create table Test_CheckSum_Record ( TableName varchar(max), CheckSum_Before int, CheckSum_After int)
SELECT name into #TempNames
FROM sys.Tables where is_ms_shipped = 0
And the pseudocode for what I want to do is something like
foreach(var name in #TempNames)
insert into Test_CheckSum_Record(name, ExecuteSQL N'select checksum_agg(binary_checksum(*)) from ' + name + ' with (nolock)', null)
But how does one do this?
Judging by the comments you need to create a trigger that handles all CRUD operations and just places a flag
Syntax is
Create TRIGGER [TriggerName] ON [TableName]
AFTER UPDATE, AFTER Delete, AFTER UPDATE
In the trigger you can do a
select CHECKSUM_AGG([Columns you want to compare against])
from [ParentTable] store that value in a variable and check it against the checksum table before column. If it does not exist you add a new entry with the DELETED tables checksum_AGG value as the before entry
Please note the choice not to use the inserted table is just preference for me on calculated columns
I will edit later when I have more time to add code
Im writing a VB app that is scrubbing some data inside a DB2 database. In a few tables i want to update entire columns. For example an account number column. I am changing all account numbers to start at 1, and increment as I go down the list. Id like to be able to return both the old account number, and the new one so I can generate some kind of report I can reference so I dont lose the original values. Im updating columns as so:
DECLARE #accntnum INT
SET #accntnum = 0
UPDATE accounts
SET #accntnum = accntnum = #accntnum + 1
GO
Is there a way for me to return both the original accntnum and the new one in one table?
DB2 has a really nifty feature where you can select data from a "data change statement". This was tested on DB2 for Linux/Unix/Windows, but I think that it should also work on at least DB2 for z/OS.
For your numbering, you might considering creating a sequence, as well. Then your update would be something like:
CREATE SEQUENCE acct_seq
START WITH 1
INCREMENT BY 1
NO MAXVALUE
NO CYCLE
CACHE 24
;
SELECT accntnum AS new_acct, old_acct
FROM FINAL TABLE (
UPDATE accounts INCLUDE(old_acct INT)
SET accntnum = NEXT VALUE FOR acct_seq, old_acct = accntnum
)
ORDER BY old_acct;
The INCLUDE part creates a new column in the resulting table with the name and the data type specified, and then you can set the value in the update statement as you would any other field.
A possible solution is to add an additional column (let's call it oldaccntnum) and assign old values to that column as you do your update.
Then drop it when you no longer need it.
Here's what I'd do:
-- create a new table to track the changes.
- with columns identifying a unique key, old-vale, new-value, timestamp
-- create a trigger on the accounts table
to write the old and new values to the new table.
But, not knowing all the conditions, it may not be worth the trouble.
Goal: When everybody else does SELECT * FROM mytable they see one version of the table. But when a specific user does SELECT * FROM mytable they see another version of the table.
I think I'm like halfway there with creating a new role and putting the single user in it. Then creating a copy of the default table with SELECT * INTO newrole.mytable FROM dbo.mytable. But when the user does SELECT * FROM mytable they still see the dbo.mytable. How do I get them to default to the newrole.mytable? I still need them to see all the other dbo tables just not this one.
Create a new schema, and a duplicate table (or view onto dbo.table if that's what you want) in it - eg., otheruser.table. Then, set the user's login to default to that schema:
USE atest
GO
CREATE ROLE [arole]
GO
CREATE SCHEMA [aschema] AUTHORIZATION [arole]
GO
CREATE USER [auser] FOR LOGIN [modify_user] WITH DEFAULT_SCHEMA = aschema
GO
EXEC sp_addrolemember 'arole', 'auser'
GO
CREATE TABLE dbo.atable ( col1 int )
GO
CREATE TABLE aschema.atable (col2 varchar(10))
GO
INSERT INTO dbo.atable( col1 ) VALUES( 1 )
GO
INSERT INTO aschema.atable( col2 ) VALUES( 'One' )
GO
PRINT 'dbo'
SELECT * FROM atable
GO
EXECUTE AS USER = 'auser'
GO
PRINT 'aschema'
SELECT * FROM atable
GO
REVERT
GO
I don't know if this may help but you may be able to make a view of a different table with the same name, here is an excerpt from http://www.w3schools.com/SQl/sql_view.asp:
In SQL, a view is a virtual table based on the result-set of an SQL statement.
A view contains rows and columns, just like a real table. The fields in a view are fields from one or more real tables in the database.
You can add SQL functions, WHERE, and JOIN statements to a view and present the data as if the data were coming from one single table.
I use Postgres primarily, so YMMV, but in postgres you need to
1) Create the new schema, preferably owned by the new role, and put the table in it
2) Set the search_path variable to include that schema BEFORE the other one.
Hope it helps.
This is a very bad idea. I'm not sure why people try all these crazy methods to improve security but it's just plain counter productive.
Ultimately every security system comes down to some line like the following if(User.HasAccessTo(object)). In fact, if you've designed a well thought out security system that's almost exactly how it should work. The more disjointed your authentication checks, the more likely you'll make a mistake. If only some users have access to certain record information you should add a flag to those records and verify access based on that.