In SQL Server (2016) we have the SESSION_CONTEXT() and sp_set_session_context to retrieve/store custom variables in a key-value store. These values are available only in the session and their lifetime ends when the session is terminated. (Or in earlier versions the good old CONTEXT_INFO to store some data in a varbinary).
I am looking for a similar solution in EXASol (6.0).
An obvious one would be to create a table and store this info there, however this requires scheduled cleanup script and more error prone than a built-in solution. This is the fallback plan, however I'd like to be sure that there is no other options.
Another option could be to create individual users in the database and configure them, but just because of the amount of users to be added, this was ruled out.
The use-case is the following: An application has several users, each user have some values to be used in each queries. The application have access only to some views.
This works wonderfully in SQL Server, but we want to test EXASol as an alternative with the same functionality.
I cannot find anything related in the EXASol Manual but it is possible, that I just missed something.
Here is a simplified sample code in SQL Server 2016
sp_set_session_context #key='filter', #value='asd', #read_only=1;
CREATE VIEW FilteredMyTable AS
SELECT Col1, Col2, Col3 FROM MyTable
WHERE MyFilterCol = CONVERT(VARCHAR(32), SESSION_CONTEXT('filter'))
I've tried an obviously no-go solution, just to test if it works (it does not).
ALTER SESSION SET X_MY_CUSTOM_FILTER = "asd"
You cannot really set a session parameter in EXASOL, the only way to achieve something similar is to store the values that you need in a table with a structure like:
SESSION_ID KEY VALUE READ_ONLY
8347387 filter asd 1
With LUA you could create a script that will make easier for you to manage these "session" variables.
I think you can achieve what you need by using the scripting capabilities within Exasol - see section 3.5 in the user manual..
You could also handle the parameterisation 'externally' via a shell script
Related
I have a very strange 'reload.sql' file that I need to use to build a database.
It references about 200 XXX.dat files with straight-up readable data (although useless without explanations regarding the meaning of the fields).
I have tried msssql server, mysql workbench (on a server local-hosted on wamp), and directly accessing it through DBeaver and IBConsole, but I cannot manage to execute/build it.
It uses a weird syntax. There are elements like
begin
...
end
go
that hinted me towards T-SQL, but using sqlcmd on it gave me thousands upon thousands of errors regarding keywords.
Specifically, the very first batch of executable lines says
SET OPTION date_order = 'YMD'
go
SET OPTION PUBLIC.preserve_source_format = 'OFF'
go
SET TEMPORARY OPTION tsql_outer_joins = 'ON'
go
SET TEMPORARY OPTION st_geometry_describe_type = 'binary'
go
SET TEMPORARY OPTION st_geometry_on_invalid = 'Ignore'
go
SET TEMPORARY OPTION non_keywords = 'attach,compressed,detach,kerberos,nchar,nvarchar,refresh,varbit'
go
which generates about 150 errors 'Incorrect syntax near OPTION keyword' on its own, and according to google is part of a 'rexx' procedure but 'date_order' should then be 'DATFMT', right?
Another track is that of SyBase, but I cannot for the life of me get it to work (through my trials I did manage to build a .db file, that, well, is useless to me since I can't build it either..).
I've tried accessing it through ODBC pilots as well but none worked (the paradox ODBC did not crash, but said there was an error with a FROM clause, which are generated automatically...).
I need to know a way to build a database from this file or directly access the data it references, which I can't really post since it contains private medical data.
Also what madman came up with this.
The very first google link (for me anyway) against 'st-geometry-describe-option' shows this is a SAP SQL Anywhere database i.e. http://dcx.sybase.com/1200/en/dbadmin/st-geometry-describe-option.html
So I would suggest starting from the SQL Anywhere documentation and you will need to install the database software beforehand.
I want to modify a column name to new name present in a table
but here problem i want to manually modify the column name present in Triggers or SP's.
Is there a any better way of doing it.
To rename a column am using this
sp_RENAME 'Tablename.old_Column', 'new_column' , 'COLUMN';
similarly how can i do it for triggers or SP's.? without opening each script?
Well, there are a bunch of 3rd party tools that are promising this type of "safe rename", some for free and some are not:
ApexSQL has a free tool for that, as MWillemse wrote in his answer,
RedGate have a commercial tool called SQLPrompt that also have a safe renaming feture, However it is far from being free.
Microsoft have a visual studio add-in called SQL Server Data Tools (or SSDT in the short version), as Dan Guzman wrote in his comment.
I have to say I've never tried any of these specific tools for that specific task, but I do have some experience with SSDT and some of RedGate's products and I consider them to be very good tools. I know nothing about ApexSQL.
Another option is to try and write the sql script yourself, However there are a couple of things to take into consideration before you start:
Can your table be accessed directly from outside the sql server? I mean, is it possible that some software is executing sql statement directly on that table? If so, you might break it when you rename that column, and no sql tool will help in this situation.
Are your sql scripting skills really that good? I consider myself to be fairly experienced with sql server, but I think writing a script like that is beyond my skills. Not that it's impossible for me, but it will probably take too much time and effort for something I can get for free.
Should you decide to write it yourself, there are a few articles that might help you in that task:
First, Microsoft official documentation of sys.sql_expression_dependencies.
Second, an article called Different Ways to Find SQL Server Object Dependencies that is written by a 13 years experience DBA,
and last but not least, a related question on StackExchange's Database Administrator's website.
You could, of course, go with the safe way Gordon Linoff suggested in his comment, or use synonyms like destination-data suggested in his answer, but then you will have to manually modify all of the columns dependencies manually, and from what I understand, that is what you want to avoid.
Renaming the Table column
Deleting the Table column
Alter Table Keys
Best way use Database Projects in Visual Studio.
Refer this links
link 1
link 2
you can do what #GorDon suggested.
Apart from this,you can also play with this query,
select o.name, sc.* from sys.syscomments sc inner join sys.objects o
on sc.id=o.object_id where sc.text like '%oldcolumnname%'
this will return list of all proc and trigger.Also you can modify filter to get exact list.then it will be very easy for you to modify,manually.
But whatever you decide,don't simply drop old column.
To be safe,even keep back up.
This suggestion relates to Oracle DB, however there may be equivalent solutions in other DBMS's.
A temporary solution to your issue is to create a pseudocolumn. This solution looks a little hacky because the syntax for a pseudocolumn requires an expression. The simplest expression I can think of is the case statement below. Let me know if you can make it more simple.
ALTER TABLE <<tablename>> ADD (
<<new_column_name>> AS (
CASE
WHEN 1=1 THEN <<tablename>>.<<old_column_name>>
END)
);
This strategy basically creates a new column on the fly by evaluating the case statement and copying the value of <<old_column_value>> to <<new_column_value>>. Because you are dynamically interpolating this column there is a performance penalty vs just selecting the original column.
The one gotcha is that this will only work if you are duplicating a column once. Multiple pseudocolumns cannot contain duplicate expressions in Oracle.
The other strategy you can consider is to create a view and you can name the columns whatever you want. You can even INSERT/UPDATE/DELETE (execute DML) against views, but this would give you a whole new table_name, not just a new column. You could however rename the old table, and name your view the same as your old table. This also has a performance penalty vs just accessing the underlying table.
You might want to replace that text in definition. However, you will be needing a dedicated administrator connection in sql server. Versions also vary in setting up a dedicated administrator connection. Setting up the startup parameter by adding ;-T7806 under advanced. And by adding Admin: before the servername upon logging in. By then, you may be able to modify the value of the definition.
I'm getting a little confused about using parameters with SQL queries, and seeing some things that I can't immediately explain, so I'm just after some background info at this point.
First, is there a standard format for parameter names in queries, or is this database/middleware dependent ? I've seen both this:-
DELETE * FROM #tablename
and...
DELETE * FROM :tablename
Second - where (typically) does the parameter replacement happen? Are parameters replaced/expanded before the query is sent to the database, or does the database receive params and query separately, and perform the expansion itself?
Just as background, I'm using the DevArt UniDAC toolkit from a C++Builder app to connect via ODBC to an Excel spreadsheet. I know this is almost pessimal in a few ways... (I'm trying to understand why a particular command works only when it doesn't use parameters)
With such data access libraries, like UniDAC or FireDAC, you can use macros. They allow you to use special markers (called macro) in the places of a SQL command, where parameter are disallowed. I dont know UniDAC API, but will provide a sample for FireDAC:
ADQuery1.SQL.Text := 'DELETE * FROM &tablename';
ADQuery1.MacroByName('tablename').AsRaw := 'MyTab';
ADQuery1.ExecSQL;
Second - where (typically) does the parameter replacement happen?
It doesn't. That's the whole point. Data elements in your query stay data items. Code elements stay code elements. The two never intersect, and thus there is never an opportunity for malicious data to be treated as code.
connect via ODBC to an Excel spreadsheet... I'm trying to understand why a particular command works only when it doesn't use parameters
Excel isn't really a database engine, but if it were, you still can't use a parameter for the name a table.
SQL parameters are sent to the database. The database performs the expansion itself. That allows the database to set up a query plan that will work for different values of the parameters.
Microsoft always uses #parname for parameters. Oracle uses :parname. Other databases are different.
No database I know of allows you to specify the table name as a parameter. You have to expand that client side, like:
command.CommandText = string.Format("DELETE FROM {0}", tableName);
P.S. A * is not allowed after a DELETE. After all, you can only delete whole rows, not a set of columns.
I have used mysql for some projects and recently I moved to postgresql. In mysql when I alter a table or a field the corresponding query will be displayed in the page. But such a feature was not found in postgresql(kindly excuse me if I'm wrong). Since the query was readily available it was very helpful for me to test something in the local database(without explicitly typing the query), copy the printed query and run it in the server. Now it seems like I've to manually do all the trick. Even though I'm familiar with the query operations,at times it can be pretty time consuming process. Can anybody help me? How can I get the corresponding query to get displayed in postgresql(like in mysql) whenever a change is made to the table?
If you use SELECT * FROM ... there should not be any reason for your output to not include newly added columns, no matter how you get your results - would that be psql in command line, PgAdmin3 or any other IDE.
After you add new columns, it is possible that these changes are still in open transaction in other window or SQL command - be sure to COMMIT such transaction. Note that your changes to data or schema will not be visible to any other database clients until transaction commits.
If your IDE still does not show changes, maybe you need to refresh list of tables or if that option is not available, restart your IDE. If that does not work still, maybe you should use better IDE.
If you have used SELECT field1, field2, ... FROM ... then you must add new fields into your SELECT statement(s) - but this would be true for any other SQL implementation, MySQL included.
You could use the LISTEN / NOTIFY mechanism in PostgreSQL to notify your client on altering the database schema.
Im having trouble identifying my databases as correct and valid version of my model. I have a GUID-id for my model I could use, but where do I put it? I dont want an entire table with only one row for this GUID. Is there any metadata-repository for databases (SQL Server 2008) or is there any other methods of identifying databases except their names? I could name the database to my model-GUID but it doesnt seem right...
The scenario is like this: I have a Entity Framework-model and I identify it by a GUID. I let the user pick a database-connectionstring and now I want to verify that its a valid database (which has been created from my app). I want to do this every time the app starts just to be sure. What Im doing now is checking that a certain table with a certain name exists but thats not good enough. I want to be 99% sure.
Edit: I would prefer to set this value from the DDL-script which is already setting up the database and I want to be able to get it from a SqlCommand in ado.net.
Use an Extended database property
In script:
USE preet;
GO
EXEC sys.sp_addextendedproperty
#name = N'myVersion',
#value = N'999-abc-123-nop';
GO
and
In the UI