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I am trying to create a stream object to insert data into a text column in SQL Server, but am not too sure how to go about it.
How would I create an IStorage object or gain access to an IStorage interface so I can use the CreateStream function?
Matt Harvey
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See IStream - Compound File Implementation[^].
Presumably you have your data either already in memory or in a disk file. If the former, you probably want to use CreateStreamOnHGlobal to wrap memory with an object that implements IStream. If the latter, see StgCreateDocfile with STGM_CONVERT. Once you've created the storage, you should be able to call IStorage::OpenStream on the newly converted "Contents" stream. As long as you don't call IStorage::Commit, the original file will not be affected.
Stability. What an interesting concept. -- Chris Maunder
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The data is in memory. This is the process I am using:
1. Execute "SELECT column FROM table" command and obtain the IRowset object.
2. Get IRowSetChange and IRowsetUpdate objects
3. Set bindings and CreateAccessor
4. Call IRowset->GetNextRows() and IRowset->GetData() to obtain row accessor.
5. Use CreateStreamOnHGlobal() to create Stream.
6. Call IRowsetChange->SetData, then IRowsetUpdate->Update
This process works ok if I bind as a simple DBTYPE_STR, but when I try to do the update using a DBTYPE_IUNKNOWN object of type IID_ISequentialStream, then update does not insert the stream object I created.
This may have something to do with it. In the bindings I specify, the only DBOBJECT flags and iid that work for the CreateAccessor call are these:
dbObject->dwFlags = STGM_READ;
dbObject->iid = IID_ISequentialStream;
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I have just realised what I have missed out here. I did a QueryInterface on the IStream to get an ISequentialStream pointer and now using that the update works.
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i'm just trying to insert some values into a table, but i got this error which says:
Operator & not defined for types System.Data.SqlTypes.SqlMoney
This is the line which gives the error:
cmd = New SqlCeCommand("INSERT INTO stock (name,price,desp) VALUES ('" & name & "', '" & newprice & "' ,'" & desp & "'')", connectionstring)
all other parts of the code work fine, which is why i'm only posting this small bit. price in my database is defined as type money, and newprice is of type SqlMoney too. Can someone help? thanks!
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You should not create SQL Statements like this if at all possible because it is vulnerable to a SQL Injection Attack.
SQL Injection Attacks and Some Tips on How to Prevent Them[^]
Some Microsoft documentation that might help:
SqlCeCommand.Parameters[^]
I've left the explanantion for your error until the end of this message as I wanted to get across the point about security your applications against attack.
The reason for your error is that SqlMoney is not a string and the & operator is used for concatenating strings together. This is an inefficient way to concatenate strings, you should consider using String.Concat() or String.Format(), the latter being more likly to understand how to insert a SqlMoney object into the string without you having to write any code to convert it yourself.
Does this help?
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i know that SqlMoney is not of a string type, but then again i'm not trying to insert a string into the query. The data type i specified in my database is of type Money, which is why i'm using SqlMoney in my code. Right now i'm thinking of ways on how to insert the value in, but its giving me errors so far.......thanks for the reply anyway.
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gundamhamtaro wrote:
i know that SqlMoney is not of a string type, but then again i'm not trying to insert a string into the query
You are trying to concatenate the SqlString object into a string. The SQL query is a string, therefore anything in the query must be converted to a string so it can be submitted to the database.
gundamhamtaro wrote:
Right now i'm thinking of ways on how to insert the value in, but its giving me errors so far
Did you read my post? Have you tried parameterised queries like I suggested? It isn't just for the security considerations. It makes converting data types to SQL much easier also.
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i tried String.format and String.Concat, and when i use String.format, i get this error: System.ArgumentNullException; and if i use Concat i get an error when trying to insert the data: the specified data type is not valid. maybe i'm doing it wrongly, so i'll just post my code:
dim price as string
price = String.Concat(newprice)
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Okay - I give up. You obviously don't want to take my advice and use parameterised queries.
String.Concat() is used with 2 or more strings. You cannot put anything in there that is not a string. SqlMoney is not a string. That is why you get an error message saying "data type is not valid".
String.Format() is used with a format string and some parameters. For example String.Format("{0}", newPrice) The value newPrice is formatted into a string. You can also do a lot more powerful things with format, but you can read that in the documentation.
Once again, I would suggest you use parameterise queries (the links I gave in past posts show examples of how to use them) because then you do not have to worry about converting data into a string in order to format them to fit in a SQL statement.
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huh??? i didnt say that i dont want to use parameterised queries did i? there was a misunderstanding, i thought that parameterised queries was something thats similar to what i had typed out. now that i've checked it, i know i was wrong and now i that i've changed it, everything works fine. thanks for everything =)
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Hopefully this is very simple - using a vb.net front end & access database for college assignment and need to write a SQL query as follows (and never having used SQL before its proving beyond me!!)
I need to apply a filter criteria within a SQL query, using a value stored in a variable.
A value is applied in a combo box, which is then stored as the variable, and another combo box should then show results filtered on the first combo box selection.
Cheers.
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So, which bit are you stuck on? Getting the value from the conbo box into the SQL? or, the SQL itself?
The SQL for Access uses a ? to denote a parameter position, which you can add in your VB.NET program using the Parameters collection on the OleDbCommand object. I hope I've supplied enough hints. I won't fully answer a homework question (for obvious reasons) and I hope you'll understand why I don't give a complete solution. But I am willing to nudge you in the right direction if necessary.  Feel free to elaborate on what you have done and where you are stuck.
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The bit I am stuck on is getting the SQL query to recognise that the value I want to search from is the value in the variable, rather than looking for the name of the variable as a value,
e.g. (its a very basic query..)
SELECT names
FROM Reservations
Where names = "name" (I don't want it to look for "name" in the query, but the value contained within "name"
Theres probably something more I need to to in the vb.net code as well but not sure what yet
Yes, its something want to/ got to learn, but have only been learning vb.net for a month and SQl for about two weeks, so hints greatly apprecaited so can move forward!
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Okay. Like I said in my previous post you can replace your search criteria with a ? which is a parameter placeholder. So, your WHERE clause will look like this:
WHERE names = ? You can then add the parameter value to your command object in VB.NET. For example:
MyCommand.Parameters.Add("search value", OleDbType.VarChar)Remember that if you have more than one parameter then the order of the parameters in VB.NET must match the order of the ?s in the SQL Statement because Access does not support named parameters (in other DBs you can use a name prefixed with an @ instead of a ?)
Here are some links to some documentation you might find useful. They also contain examples of how to create a Command with parameters and run it:
OleDbCommand.Parameters[^]
OleDbParametersCollection.Add()[^]
OleDbType[^] enumerations
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Many thanks, you have been most helpful, I have more of an idea how to approach this now, will give it a try.
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Firstly, i'm very new to Sql Server 2000.
I'm just wondering why there isn't an option in the Enterprise Manager for selecting a database and executing SQL from a file on it.
I've been using the osql command in the command prompt to perform my sql functions (create table, drop, alter, etc..) but i need to modify each one by specifying the (USE myDB) and then GO.
Do i need to go through DTS and all that package stuff or is there an easier way? I havn't touched the Query Analyzer yet.
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I open up query analyzer and click the drop down up top to choose my db and then copy and paste the sql file into it and click the run button...
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I have the following problem. I have two columns. One is a number, the other is a name. I want to make a calculation that sums ONLY where the name is the same. For example:
Name Value CALCULATEDVALUE
Bob 3 9
Bob 2 9
Alice 1 1
Bob 4 9
Carol 2 5
Carol 3 5
How do I go about doing this? I don't have the faintest clue.
Thanks a lot!
Did I post well? Rate it! Did I post badly? Rate that too!
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Use the GROUP BY clause.
SELECT Name, SUM(Value)
FROM MyTable
GROUP BY Name If you need the output to be like the table you have above, you will need to create a subquery and join to it, like this:
SELECT Name, Value, GroupValue
FROM MyTable
INNER JOIN (SELECT Name, SUM(Value) AS GroupValue
FROM MyTable
GROUP BY Name) AS Group ON Group.Name = MyTable.Name
Does this help?
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Hello Friends
Someone know some article about "Database SQL Syntax Comparison" among:
- SQL Server 2000
- SQL Server 2005
- Firebird
- Interbase
- MySQL
- PostgreSql
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Oops... I forgot:
- Oracle
Thanks for all!
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Does anyone have an example of code required to connect to an AS400. I am new to .Net and looking for the best way.
Thanks
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