How do sqlite's tcl bindings work? Looking at an example snippet, the sqlite3 procedure seems to open the given database and then - I guess - define a procedure db1 which dispatches on the eval method?
sqlite3 db1 ./testdb
db1 eval {CREATE TABLE t1(a int, b text)}
I would have expected that I can somehow create a database object that I can pass around as a parameter in other procedures and return from a proc connect procedure for example.
The sqlite3 command creates another Tcl command (implemented in C, so formally not a procedure) whose name is given by the first argument. That command in turn encapsulates the connection handle to the database.
If you want to return the handle, just return the name (db1 in this case). But you can also do it the other way round, and have the caller suggest what name to use. Either way works.
Note that this is a model that's used quite a few other places in object-oriented coding in Tcl, where it is common for the caller to suggest the name of the object, which is conceptually both handle and command. Or the object engine can be told to pick a name itself. (The exact preferred syntax for this has varied over the years.) Once the object is made, method calling then becomes naturally geared to parsing the first argument to the handle command.
Related
I found a query like select cast (:v as customtabletype) from dual.
Not able to understand what is the meaning of above line, written as dynamic query.
:<variablename>, in your case ":v", is what is known as a bind variable.
Essentially, this is a placeholder which is replaced with another value as the SQL statement is executed.
For more in-depth reading it is probably worth looking for bind variables in the Oracle documentation, as there is a lot of information available on why they're used and their benefits.
I used Listing 3 in the following link to create a FIELDPROC program QGPL/MOBHOMEPAS which should encrypt a variable char column Field Encryption in DB2 for i
I compiled the RPGLE program and I created a separate database DBMLIB/UMAAAP00 as follows
A R UMAAAF00 TEXT('-
A TEST ENCRYPTION')
A*
A IPIAAA 20A VARLEN(20)
A KYGAAA 11S 2 COLHDG('SALARY')
I then use strsql to alter the table and protect IPIAAA
ALTER TABLE DBMLIB/UMAAAP00 alter column IPIAAA set FIELDPROC
QGPL.MOBHOMEPAS
ALTER COMPLETED FOR TABLE UMAAAP00 IN DBMLIB.
For some reason when I go in to add entries through upddta directly to the file itself and then do a wrkqry to query and file and view them I don't see them as encrypted.
Is this not how it's supposed to work? Is anyone able to assist me with the logic? Ultimately, I'd like to create a simple table from scratch that has a single 20 character or so password column as encrypted.
If the code being utilized for the named FieldProc program QGPL.MOBHOMEPAS was modeled-after [an effective copy of] the source code that was found at the URL from the OP [which BTW includes a position-to request to the comments section... Why?], then that code is implemented using the base-level of the DB2 for IBM i 7.1 SQL FieldProc support, not the next [enhanced] level of support in which the masking feature was added. That is, every invocation other than for function-code=8 will necessarily always be an Encode or a Decode operation for which any masking of the data is unsupported, because changing the data [with that level of support] would corrupt the data in the TABLE.
Note [from http://www.mcpressonline.com/rpg/db2-field-procedures-finally-support-conditional-masking.html] the differences in the coding requirements described for the pre-masking-support [eight parameters] and since-masking-support [nine parameters] as the pre-requisite to have the Run Query (RUNQRY) and Update Data (UPDDTA) features mask the data that is presented to the user:
The new FieldProc Masking support revolves around two main components.
The first component is a new parameter that was added to the parameter
lists that the DB2 engine passes to the FieldProc program on each
decode call. This new parameter controls whether or not the FieldProc
program can return a masked value. There are some DB2 operations—such
as the RGZPFM (Reorganize Physical File Member) command and trigger
processing—that always require the clear-text version of the data to
be returned. The second component is a new special SQLState value
('09501') that is to be returned by the FieldProc program whenever it
is passed a masked value on the encode call. This prevents the masked
value from being encoded, which would result in the original data
value being lost. When this special SQLState value is returned, DB2
will ignore the encoded value that is passed back by the FieldProc
program and instead use the value that's currently stored in the
record image for that column.
For some reason when I go in to add entries through upddta directly to
the file itself and then do a wrkqry to query and file and view them I
don't see them as encrypted. Is this not how it's supposed to work?
No, that's not how it's supposed to work. The data will be encoded on disk only.
When you view the data it will be decoded automatically by the FIELDPROC program no matter what you're using to view it (WRKQRY [yuck], DFU, STRSQL, whatever). This is how it works regardless of field masking (which is different/additional functionality).
I would like to know how to accomplish this task. I've looked at CASE, DECODE or IF condition and I'm not able to make it work. My goal is to pass a block of predefined column/value pair constructed from ASP.NET data to my Oracle stored procedure. I am trying to only update certain columns out of many to preserve other columns not needing updates. So here's my set up:
Stored procedure:
UpdateSelectedColumns(myValuePairString, updatedBy)
-- Passed variable from ASP.NET, myValuePairString = 'col1 = 10,col2 = 'Dog''
-- update statement final
UPDATE MyTable
SET
col1 = 10,
col2 = 'Dog'
col3 = 'john';
COMMIT;
Thank you in advance...
Ricky
For once I'm gonna advise to not use a stored proc. There is no point here in using a stored procedure.
As it is your stored procedure would blindly accept its arguments and execute the update without adding any value. Furthermore, by using this procedure, you preclude the use of binds and exposes yourself to bugs (whenever you encouner a value with a quote '), performance hit and SQL injection vulnerability.
The advantage of PL/SQL (simple transparent binding, transparent use and reuse of cursors, strict static SQL parsing and metadata dependancy) are all pointless if you take an aribtrary string as argument and put it in a dynamic cursor.
You'll be better off to use your language native cursors and use bind variables.
If you really want to use PL/SQL, replace your single argument with a couple of tables. One for the column names, one for the variable values. You could then use DBMS_SQL to parse the statement and use appropriate bind variables. You'll need some convention to be able to parse date, number and character values. You'll need to read metadata from the database to check the datatypes. This would be a lot of code for not a bit of value.
I have a sqlite3 prepared statement. I know the number of values to bind to this prepared statement, but don't know their data types. (I just get a CSV file with the right values). Is there a generic bind method I can use for this? All the bind method in the documentation are for a specific data type.
I know that sqlite3 uses a dynamic type system. But it doesn't help if you are using the C API due to the absence of a generic bind method.
Any ideas/tricks anyone has tried?
The C API does not have a generic bind method because the C language does not have a generic type. Simply use the bind method for the type that you have, if it is wrong then sqlite will convert it for you.
I need to be able to run a query such as
SELECT * FROM atable WHERE MyFunc(afield) = "some text"
I've written MyFunc in a VB module but the query results in "Undefined function 'MyFunc' in expression." when executed from .NET
From what I've read so far, functions in Access VB modules aren't available in .NET due to security concerns. There isn't much information on the subject but this avenue seems like a daed end.
The other possibility is through the CREATE PROCEDURE statement which also has precious little documentation: http://msdn.microsoft.com/en-us/library/bb177892%28v=office.12%29.aspx
The following code does work and creates a query in Access:
CREATE PROCEDURE test AS SELECT * FROM atable
However I need more than just a simple select statement - I need several lines of VB code.
While experimenting with the CREATE PROCEDURE statement, I executed the following code:
CREATE PROCEDURE test AS
Which produced the error "Invalid SQL statement; expected 'DELETE', 'INSERT', 'PROCEDURE', 'SELECT', or 'UPDATE'."
This seems to indicate that there's a SQL 'PROCEDURE' statement, so then I tried
CREATE PROCEDURE TEST AS PROCEDURE
Which resulted in "Syntax error in PROCEDURE clause."
I can't find any information on the SQL 'PROCEDURE' statement - maybe I'm just reading the error message incorrectly and there's no such beast. I've spent some time experimenting with the statement but I can't get any further.
In response to the suggestions to add a field to store the value, I'll expand on my requirements:
I have two scenarios where I need this functionality.
In the first scenario, I needed to enable the user to search on the soundex of a field and since there's no soundex SQL function in Access I added a field to store the soundex value for every field in every table where the user wants to be able to search for a record that "soundes like" an entered value. I update the soundex value whenever the parent field value changes. It's a fair bit of overhead but I considered it necessary in this instance.
For the second scenario, I want to normalize the spacing of a space-concatenation of field values and optionally strip out user-defined characters. I can come very close to acheiving the desired value with a combination of TRIM and REPLACE functions. The value would only differ if three or more spaces appeared between words in the value of one of the fields (an unlikely scenario). It's hard to justify the overhead of an extra field on every field in every table where this functionality is needed. Unless I get specific feedback from users about the issue of extra spaces, I'll stick with the TRIM & REPLACE value.
My application is database agnostic (or just not very religious... I support 7). I wrote a UDF for each of the other 6 databases that does the space normalization and character stripping much more efficiently than the built-in database functions. It really annoys me that I can write the UDF in Access as a VB macro and use that macro within Access but I can't use it from .NET.
I do need to be able to index on the value, so pulling the entire column(s) into .NET and then performing my calculation won't work.
I think you are running into the ceiling of what Access can do (and trying to go beyond). Access really doesn't have the power to do really complex TSQL statements like you are attempting. However, there are a couple ways to accomplish what you are looking for.
First, if the results of MyFunc don't change often, you could create a function in a module that loops through each record in atable and runs your MyFunc against it. You could either store that data in the table itself (in a new column) or you could build an in-memory dataset that you use for whatever purposes you want.
The second way of doing this is to do the manipulation in .NET since it seems you have the ability to do so. Do the SELECT statement and pull out the data you want from Access (without trying to run MyFunc against it). Then run whatever logic you want against the data and either use it from there or put it back into the Access database.
Why don't you want to create an additional field in your atable, which is atable.afieldX = MyFunc(atable.afield)? All what you need - to run UPDATE command once.
You should try to write a SQL Server function MyFunc. This way you will be able to run the same query in SQLserver and in Access.
A few usefull links for you so you can get started:
MSDN article about user defined functions: http://msdn.microsoft.com/en-us/magazine/cc164062.aspx
SQLServer user defined functions: http://www.sqlteam.com/article/intro-to-user-defined-functions-updated
SQLServer string functions: http://msdn.microsoft.com/en-us/library/ms181984.aspx
What version of JET (now called Ace) are you using?
I mean, it should come as no surprise that if you going to use some Access VBA code, then you need the VBA library and a copy of MS Access loaded and running.
However, in Access 2010, we now have table triggers and store procedures. These store procedures do NOT require VBA and in fact run at the engine level. I have a table trigger and soundex routine here that shows how this works:
http://www.kallal.ca/searchw/WebSoundex.htm
The above means if Access, or VB.net, or even FoxPro via odbc modifies a row, the table trigger code will fire and run and save the soundex value in a column for you. And this feature also works if you use the new web publishing feature in access 2010. So, while the above article is written from the point of view of using Access Web services (available in office 365 and SharePoint), the above soundex table trigger will also work in a stand a alone Access and JET (ACE) only application.