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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!
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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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Does anyone know how to transfer an entire database out of mssql server 2005 (express) into a .sql file so I can recreate it? I have looked though the TSQL commands on msdn and tried bcp (unless I'm missing somthing that will only do tables and I need the stored procedures as well) The reason for this is I want to export the data and put it into a ms sql 2000 database but dts won't work because the database is so different (neither will the sp_attach_db stored procedure (gives an error about indexes)
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I've not had a chance to play around with SQL Server 2005, but in SQL Server 2000 the Enterprise Manager has a feature where you can script database objects (tables, views, stored procedures, user defined functions, etc.) by right clicking on them and selecting the Script item. You can also click on the database to script the whole DB. I'm guessing that SQL Server 2005 will have something similar.
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that's the problem  the express version of 2005 doesn't have enterprise manager, it has a community built one that doesn't have much funtionality right now. The higher versions of 2005 are suppose to have this but not express (express is the msde of 2005)
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it has all the *funtionality* but not the tools (oh and 1 gig ram usage is the other limitation)
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SQL Express Manager is supposed to have this capability.
Download from here[^]. Note that the version of Express Manager needs to match the version of SQL Server Express, so you'll need to upgrade your database server to the April CTP to match the currently-available Express Manager CTP.
Stability. What an interesting concept. -- Chris Maunder
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I have that but the problem is it's not in it yet... or if it is I haven't found it...
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Hello:
I get this error when trying to add a series of datarows to a datatable
Any Ideas, Here Is the Code:
Public SaveIt()
{
DataRow dr;
for(int i=0;i<12;i++)
{
dr["Months"] = arrMonths[i]; //Throws Exception
MyDataTable.Rows.Add(dr);
}
MyDatSet.GetChanges();
MyDataSet.WriteXml(strFileName, XmlWriteMode.DiffGram);
}
TIA
GostWrtyer
}
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GostWryter wrote:
I get this error when trying to add a series of datarows to a datatable
"this" has no associated context as you have not actually given an error message.
There is no data row object here.
DataRow dr; does not actually create a DataRow object, only a reference to one, and since you don't reference one then the line fails because you are trying to use a DataRow that does not exist.
To create an appropriate DataRow object use DataTable.NewRow()[^] before trying to use dr. e.g.
dr = MyDataTable.NewRow();
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Colin Angus Mackay wrote:
"this" has no associated context as you have not actually given an error message.
Yes he has, it's in the subject line 
Seriously, while looking at the code, I would expect that it would generate an "Object instance not set to an object" exception instead of that column not found in table.
For GostWryter, yes, the solution given by Colin should fix your problem. A little more explanation. You need to use the DataTable to create a new DataRow so the row contains the table's schema (columns for example), even if the row itself is not in the table yet (that's why you Add it to the Rows collection later.)
-- LuisR
Luis Alonso Ramos
Intelectix - Chihuahua, Mexico
Not much here: My CP Blog!
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