SQL Server parameterized query with a WHERE clause with Nulls - sql-server

VB.NET 2012, ADO.NET, SQL Server 2014
I setup a parameterized query that works well. I essentially read records from a DataTable that comes from a different source than my SQL Server. It's small enough that I elected to read record by record and build a query and hit the SQL Server for a match.
However I am having trouble getting a match when one of my fields is supposed to be matched for a null. I know a record exist because I can look at it in SQL Server directly and see it. With my parameterized query somehow the null is being translated improperly. I tried manually replacing the parameter #EngSerialNo with DBNull.Value and still doesn't work. Almost seems like I need two different queries depending if my DataTable value is null.
sqQry.AppendLine("SELECT CityCode,CarNum,RegNum,Event,EngSerialNum)")
sqQry.AppendLine("FROM [MyDB].[dbo].[Events]")
sqQry.AppendLine("WHERE (CityCode=#City AND CarNum=#CarNo AND RegNum=#RegNo AND Event=#Event AND EngSerialNum=#EngSerialNo)") 'this looks for a value in EngSerialNo
'sqQry.AppendLine("WHERE (CityCode=#City AND CarNum=#CarNo AND RegNum=#RegNo AND Event=#Event AND EngSerialNum IS NULL)") 'this looks for a Null in EngSerialNo
Dim cmd As New SqlCommand
With cmd
.Connection = connMyDb
.CommandType = CommandType.Text
.CommandText = sqQry.ToString
'cycle through each DataRow in the DataTable and check for returns
Dim total As Integer = 0
For Each row As DataRow In dtMain.Rows
.Parameters.Clear()
.Parameters.AddWithValue("#City", row.Item("City"))
.Parameters.AddWithValue("#CarNo", row.Item("CarNo"))
.Parameters.AddWithValue("#RegNo", row.Item("RegNo"))
.Parameters.AddWithValue("#Event", row.Item("Event"))
.Parameters.AddWithValue("#EngSerialNo", row.Item("EngSerialNo")) 'how do I get this to look for a null value when the DataTable contains a null value?
Dim rowsAffected As Integer = .ExecuteNonQuery()
total += rowsAffected
Next row
End With
Update: I ended up creating a dynamic SQL for every DataRow. Basically for each DataRow I check key fields for NULL or an actual value and create the appropriate SQL command text. I have 4 fields that could contain a NULL but for sake of simplicity I only demonstrated one here. I think the developer can follow the example to create their own query.
Dim cmd As New SqlCommand
With cmd
.Connection = connMyDb
.CommandType = CommandType.Text
'cycle through each DataRow in the DataTable and check for returns
Dim total As Integer = 0
For Each row As DataRow In dtMain.Rows
.CommandText = BuildSql(row)
.Parameters.Clear()
.Parameters.AddWithValue("#City", row.Item("City"))
.Parameters.AddWithValue("#CarNo", row.Item("CarNo"))
.Parameters.AddWithValue("#RegNo", row.Item("RegNo"))
.Parameters.AddWithValue("#Event", row.Item("Event"))
.Parameters.AddWithValue("#EngSerialNo", row.Item("EngSerialNo"))
Dim rowsAffected As Integer = .ExecuteNonQuery()
total += rowsAffected
Next row
End With
Private Function BuildSql(ByVal dr As DataRow) As String
Dim sqQry As New StringBuilder
sqQry.AppendLine("SELECT CityCode,CarNum,RegNum,Event,EngSerialNum)")
sqQry.AppendLine("FROM [MyDB].[dbo].[Events]")
If dr.Item("EngSerialNo") Is DBNull.Value Then
sqQry.AppendLine("WHERE (CityCode=#City AND CarNum=#CarNo AND RegNum=#RegNo AND Event=#Event AND EngSerialNum IS NULL)") 'this looks for a Null in EngSerialNo
Else
sqQry.AppendLine("WHERE (CityCode=#City AND CarNum=#CarNo AND RegNum=#RegNo AND Event=#Event AND EngSerialNum=#EngSerialNo)") 'this looks for a value in EngSerialNo
End If
Return sqQry.ToString
End Function

In SQL you can't compare null values, i.e. EngSerialNum = null always evaluates to false, even if the value in the field is null.
Either you can create the query dynamically so that you use is null to match the null values, or you can use an expression like this:
((EngSerialNum is null and #EngSerialNo is null) or EngSerialNum = #EngSerialNo)

Related

Display value from SQL Server on a VB.NET label

I want to get a value from a SQL Server column ID and show it on label.text with help the of following code:
Sub getID()
Dim selquery As String = ("select max(id)+1 from picture1")
Dim command As New SqlCommand(selquery, con)
con.Open()
Label1.Text = (command.ExecuteScalar)
con.Close()
End Sub
The scenario is to get maximum value from ID make it plus 1, and assign it to label.text, it works correctly when I have at least one record in my SQL Server table but if I have no record in my table picture1 then it shows error
You can leverage the ISNULL T-SQL function to deal with this:
SELECT ISNULL(MAX(id), 0) + 1 from picture1
If you have no records in your table, the max(id) part will return null, and you cannot +1 to a null.
To work around that problem use the COALESCE operator, like:
COALESCE(MAX(ID), 0) + 1
If there is a value returned from max(id) it will use that, otherwise it will return 0
The return value of command.ExecuteScalar is of type Object, so you have to check the value.
This should work:
Dim objResult As Object = command.ExecuteScalar
Dim intResult As Integer = If(TypeOf objResult Is Integer, DirectCast(objResult, Integer), 0)
Label1.Text = intResult.ToString
Also you should switch Option Strict On

SqlDataAdapter.Update not updating

(I should say that im fairly new to vb.net)
I'm having a problem overwriting the entries in my database. I think the problem is that SqlDataAdapter.Update isn't overwriting the database properly with the new datatable info that i've created.
As I understand it, it should totally replace the the info in the database with the datatable when i tell it to update... no?
Here's the problem in a nutshell:
Basically, I have a database (.mdf file) with a table in it called 'test'. I've used SqlDataAdapter to make a dataset using 'test'. I have another datatable that I've made from parsing in a csv - it's called 'ToLoad'. I now want to clear the 'test' datatable, copy in all entries from the csv datatable, then save this to the database.
I've debugged all this and it all seems to work ok, except when I use SqlDataAdapter.Update I get an error telling me I cant duplicate the primary key. This is because the old entries aren't being cleared from the database entirely, before the new ones are being entered from the datatable.
I've checked that the test datatable is being actually cleared early on in the code... and it is.
I've checked that the new csv entries are being copied to the 'test' datatable... and they are.
Any help you can give on this would be really appreciated
Thanks
Craig
'MAKE A NEW SQL CONNECTION
Dim DBConnection As New SqlConnection
'SET THE CONNECTION STRING.
DBConnection.ConnectionString = "Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=C:\Project\Members.mdf;Integrated Security=True"
'OPEN THE CONNECTION TO THE DATABASE
DBConnection.Open()
'OPEN AN ADAPTER AND SELECT EVERYTHING FROM THE 'TEST' TABLE
Dim mySqlDataAdapter As New SqlDataAdapter("SELECT * FROM Test", DBConnection)
Dim mySqlCommandBuilder As New SqlCommandBuilder(mySqlDataAdapter)
Dim DBDataset As DataSet = New DataSet
'FILL THE DATASET WITH THE TEST TABLE
mySqlDataAdapter.Fill(DBDataset, "Test")
'CLEAR ALL ENTRIES IN THE DATATABLE (SO I CAN FILL IT FROM SCRATCH)
DBDataset.Tables("test").Clear()
''SET UP A LOOP TO ADD EACH RECORD FROM THE CSV DATATABLE TO THE DATABASE DATATABLE
Dim CSV_row_number As Int16
CSV_row_number = ds.Tables("toload").Rows.Count
Dim i As Int16
i = 0
Do Until i = CSV_row_number - 1
'MAKES TWO NEW DATAROW OBJECTS
Dim DB_row As DataRow
Dim CSV_row As DataRow
'SET THE CSV_ROW OBJECT EQUAL TO ROW(i) OF THE CSV DATATABLE
CSV_row = ds.Tables("toload").Rows(i)
DB_row = DBDataset.Tables("test").NewRow()
'THIS SETS ALL OF THE COLUMNS IN THIS NEW ROW AS EQUAL TO ROW1 IN THE CSV DATATABLE
DB_row("Name") = CSV_row("Name")
DB_row("Quality") = CSV_row("Address")
DBDataset.Tables("test").Rows.Add(DB_row)
i = i + 1
Loop
mySqlDataAdapter.Update(DBDataset.Tables("Test"))
I managed to fix this myself after a fair bit of googling and some trial and error. Posting my code in case it's useful for anyone else
Craig
'MAKE A NEW SQL CONNECTION
Dim DBConnection As New SqlConnection
'SET THE CONNECTION STRING. YOU GET THIS BY GOING TO SERVER EXPLORER, THEN CLICKING ON THE DATABASE
'THE CONNECTION STRING IS IN PROPERTIES
DBConnection.ConnectionString = "Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=C:\Users\ME\Project\Members.mdf;Integrated Security=True"
'OPEN THE CONNECTION TO THE DATABASE
DBConnection.Open()
'THIS OPENS AN ADAPTER TO THE DATABASE, AND SELECTS EVERYTHING FROM THE 'TEST' TABLE IN THAT DATABASE
Dim mySqlDataAdapter As New SqlDataAdapter("SELECT * FROM MemberList", DBConnection)
'THIS LETS US USE SQL ON THE DATATABLE (IT GETS PASSED THE ABOVE SQL STATEMENT)
Dim mySqlCommandBuilder As New SqlCommandBuilder(mySqlDataAdapter)
'THIS MAKES ANOTHER NEW DATASET
Dim DBDataset As DataSet = New DataSet
''THIS FILLS THAT DATASET WITH THE TEST TABLE (WHICH THE DATA ADAPTOR GRABBED ABOVE)
mySqlDataAdapter.FillSchema(DBDataset, SchemaType.Source, "MemberList")
mySqlDataAdapter.Fill(DBDataset, "MemberList")
'THIS MAKES A NEW DATATABLE
'I THEN MAKE ALL CHANGES NEEDED
Dim EDITmembers As DataTable
EDITmembers = DBDataset.Tables("MemberList")
''FIRST, IM GOING TO CLEAR ALL ENTRIES IN THE DATATABLE (SO I CAN FILL IT FROM SCRATCH)
'COUNT THE NUMBER OF ENTRIES TO CLEAR
Dim RowsInDB As Integer
RowsInDB = EDITmembers.Rows.Count()
'SET UP A LOOP TO CLEAR THEM
Dim Data_row As DataRow
Dim k As Integer = 0
Do Until k = RowsInDB
Data_row = EDITmembers.Rows(k)
Data_row.Delete()
k = k + 1
Loop
'ONCE ALL THE ROWS ARE CLEARED, SAVE THE CHANGES BY UPDATING THE ACTUAL DATABASE
mySqlDataAdapter.Update(DBDataset, "MemberList")
''THEN I SET UP A LOOP TO ADD EACH RECORD FROM THE CSV DATATABLE TO THE DATABASE DATATABLE
''I FIRST NEED TO KNOW HOW MANY ITERATIONS OF THE LOOP TO DO
Dim CSV_row_number As Int16
'COUNT THE NUMBER OF ROWS AND SET THE ABOVE INT EQUAL TO THIS
CSV_row_number = ToLoad.Rows.Count
Dim j As Int16
j = 0
Do Until j = CSV_row_number - 1
'THIS MAKES TWO NEW DATAROW OBJECTS
Dim DB_row As DataRow
Dim CSV_row As DataRow
'THIS SETS THE CSV_ROW OBJECT EQUAL TO THE FIRST ROW OF THE CSV DATATABLE
CSV_row = ToLoad.Rows(j)
'THIS SETS DB_ROW EQUAL TO A NEW ROW IN THE DATATABLE MADE FROM THE DATABASE
DB_row = EDITmembers.NewRow()
'THIS SETS ALL OF THE COLUMNS IN THIS NEW ROW AS EQUAL TO THE CORRESPONDING ROW IN THE CSV DATATABLE
DB_row("Contact Name") = CSV_row("Contact Name")
DB_row("Do not mail") = CSV_row("Do not mail")
DB_row("Membership Type") = CSV_row("Membership Type")
DB_row("Street Address") = CSV_row("Street Address")
DB_row("Supplemental Address 1") = CSV_row("Supplemental Address 1")
DB_row("Supplemental Address 2") = CSV_row("Supplemental Address 2")
DB_row("City") = CSV_row("City")
DB_row("Postal Code") = CSV_row("Postal Code")
DB_row("Email") = CSV_row("Email")
DB_row("Phone (primary)") = CSV_row("Phone (primary)")
EDITmembers.Rows.Add(DB_row)
j = j + 1
Loop
'UPDATE THE DATABASE WITH ALL THE CHANGES
mySqlDataAdapter.Update(DBDataset, "MemberList")
MessageBox.Show("done!")

Best method for importing data from text file into MS SQL Server

In need of your opinions. Currently developing an application in VB.NET.
I have a text file which contains more than one thousand rows. Each rows contains the data needed to be inserted into the database. A sample of a row is as follows:
0001--------SCOMNET--------0.100---0.105
At first glance, one might figured that each column was separated with a tab but actually each column was separated by blank spaces (I used '-' to denote as blank spaces because somehow could not get SO text editor to show the blank spaces).
The first column is defined by
Substring(0, 12) which is the data [0001--------]
second column
Substring(12, 12) in which the data is [SCOMNET-----]
third column is
Substring(24, 8) in which the data is [---0.100]
and last column is
Substring(32, 8) in which the data is [---0.105]
My initial though is to extract the lines for the text file and stored in as a list of strings, then while looping, do the separation of the each string item in the list with the SubString() function and insert it one by one until the end of the list. But this will no doubt takes time.
In my scenario, how can I take advantage of the SqlBulkCopy? Or if there is any other ways to approach this for a faster insert? Say;
open file
start loop
read line
separate each column in the line with substring
save in a DataTable
end loop
BCP(DataTable)
This includes a method that may be a more efficient way of reading your text file.
Sub readFixWidthTextFileIntoSqlTable()
Dim sqlConn As New SqlConnection("Connection String Goes Here")
sqlConn.Open()
Dim sqlComm As New SqlCommand
sqlComm.Connection = sqlConn
sqlComm.CommandType = CommandType.Text
sqlComm.CommandText = "INSERT INTO YourTableNameHere VALUES(#Field1, #Field2, #Field3, #Field4)"
sqlComm.Parameters.Add("#Field1", SqlDbType.Text)
sqlComm.Parameters.Add("#Field2", SqlDbType.Text)
sqlComm.Parameters.Add("#Field3", SqlDbType.Text)
sqlComm.Parameters.Add("#Field4", SqlDbType.Text)
Using IFReader As New FileIO.TextFieldParser(FileNameWithPath)
IFReader.TextFieldType = FileIO.FieldType.FixedWidth
IFReader.SetFieldWidths(12, 12, 8, 8)
While Not IFReader.EndOfData
Dim fields As String() = IFReader.ReadFields
sqlComm.Parameters("#Field1").Value = fields(0)
sqlComm.Parameters("#Field2").Value = fields(1)
sqlComm.Parameters("#Field3").Value = fields(2)
sqlComm.Parameters("#Field4").Value = fields(3)
sqlComm.ExecuteNonQuery()
End While
End Using
sqlConn.Close()
End Sub
You've got it pretty much right. This approach is one that I take a lot. Here's a bit of sample code to get you started. It is ONLY an example, there's absolutely no validation or and no consideration for Primary Keys on the table. If you want to review your question with more details of the structure of the destination table then I can make this example much more specific.
Read_File:
Dim sFileContents As String = ""
Using sRead As New StreamReader("e:\ExampleFile.txt")
sFileContents = sRead.ReadToEnd
End Using
Dim sFileLines() As String = sFileContents.Split(vbCrLf)
Connect_To_DB:
Dim sqlConn As New SqlConnection
sqlConn.ConnectionString = "Data Source=YourServerName;Initial Catalog=YourDbName;Integrated Security=True"
sqlConn.Open()
Setup_DataTable:
Dim ExampleTable As New DataTable
ExampleTable.Load(New SqlCommand("Select Top 0 * From Example_Table", sqlConn).ExecuteReader)
'This is not absolutely necessary but avoids trouble with NOT NULL columns (like keys)'
For Each dcColumn As DataColumn In ExampleTable.Columns : dcColumn.AllowDBNull = True : Next dcColumn
Save_To_DataTable:
For Each sLine In sFileLines
Dim ExampleRow As DataRow = ExampleTable.NewRow
ExampleRow("First_Column_Name") = sLine.Substring(0, 12).TrimEnd
ExampleRow("Second_Column_Name") = sLine.Substring(12, 12).TrimEnd
ExampleRow("Third_Column_Name") = sLine.Substring(24, 8).TrimEnd
ExampleRow("Fourth_Column_Name") = sLine.Substring(32, 8).TrimEnd
ExampleTable.Rows.Add(ExampleRow)
Next
Update_Database:
If ExampleTable.Rows.Count <> 0 Then
Dim sqlBulk As SqlBulkCopy = New SqlBulkCopy(sqlMvConnection)
sqlBulk.DestinationTableName = "Example_Table"
sqlBulk.WriteToServer(ExampleTable)
End If
Disconnect_From_DB:
sqlConn.Close()
Also, as commented on above and if you have access to it SSIS will do this in a jiffy.

Compare values in DGV column with database values and add value to new DGV column

So, Access database has two columns 1st is seller name (SELLER) and second is it's code (CODE). Access database is database with all SELLER CODEs.
DGV is populated from other source and consists of some of CODEs from Access database.
DGV has one column with codes.
I would like to create and populate new column (SELLERNAME) in DGV with SELLER names based on DGV codes and Access database CODEs.
I am going to give an example since it's hard for me to explain this better :
DGV : Column 0, 1st value = 0055, in Access database code 0055 corresponds to the name John
so I would like to put name "John" in DGV Column1, 1st value, nest to "0055" and so on
Here is my code so far :
DataGridView1.Columns.Add("SELLERNAME", "SELLERNAME") '1
Dim cn As OleDb.OleDbConnection
Dim cmd As OleDb.OleDbCommand
Dim odr As OleDb.OleDbDataReader
Dim strSQL As String
cn = New OleDb.OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=w:\SCodes.MDB")
strSQL = "SELECT SELLER, CODE FROM SCBASE"
cn.Open()
cmd = New OleDb.OleDbCommand(strSQL, cn)
odr = cmd.ExecuteReader(CommandBehavior.CloseConnection)
Do While odr.Read
For i As Integer = 0 To DataGridView1.Rows.Count - 1
DataGridView1.Rows(i).Cells(1).Value = odr.GetValue(1).ToString()
Next
Loop
I don't know what to do next after line For i As Integer = 0 To DataGridView1.Rows.Count - 1.
EDIT :
I think I am close but I need help with one line of code :
Using sqlconn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=w:\SCodes.mdb")
Using sqlcmd = New OleDbCommand("Select SELLER, CODE From SCBASE Where CODE = #CODE ", sqlconn)
sqlcmd.Parameters.AddWithValue("#CODE ", DataGridView1.Rows(i).Cells(0).Value) 'HOW TO ADD THIS LINE IN LOOP BELOW
sqlconn.Open()
Dim result = sqlcmd.ExecuteReader()
Do While (result.Read())
For i As Integer = 0 To DataGridView1.Rows.Count - 1
DataGridView1.Rows(i).Cells(1).Value = (result("DOBAVLJAC"))
Next
Loop
End Using
End Using
I had no success with a trial and error. I am trying to put this line sqlcmd.Parameters.AddWithValue("#CODE ", DataGridView1.Rows(i).Cells(0).Value) in loop below but I am getting all sorts of error.
Yes, you are very close. You just need to .Add the Parameter outside the loop and then set its .Value inside the loop like this
Using sqlconn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=w:\SCodes.mdb")
sqlconn.Open()
Using sqlcmd = New OleDbCommand("Select SELLER, CODE From SCBASE Where CODE = ?", sqlconn)
sqlcmd.Parameters.Add("?", OleDbType.VarWChar, 255)
sqlcmd.Prepare()
For i As Integer = 0 To DataGridView1.Rows.Count - 1
sqlcmd.Parameters(0).Value = DataGridView1.Rows(i).Cells(0).Value
Using result = sqlcmd.ExecuteReader()
If result.Read() Then
DataGridView1.Rows(i).Cells(1).Value = result("SELLER")
End If
End Using
Next
End Using
End Using

Visual Studio 2005 error with Unicode

Dim findTheseVals(1) As Object
' Set the values of the keys to find.
Dim myDAgn As New SqlDataAdapter
findTheseVals(0) = pDivisionno
findTheseVals(1) = pGNe
sqlCon.Open()
Dim myDSGN As New DataSet
myDAgn.SelectCommand = New SqlCommand("SELECT * FROM Villages", sqlCon)
myDAgn.Fill(myDSGN, "Villages")
myPrimaryKey(0) = myDSGN.Tables("Villages").Columns("DivisionNo")
myPrimaryKey(1) = myDSGN.Tables("Villages").Columns("VillageSin")
myDSGN.Tables("Villages").PrimaryKey = myPrimaryKey
Dim myRow As DataRow
myRow = myDSGN.Tables("Villages").Rows.Find(findTheseVals)
If Not (myRow Is Nothing) Then
isExistsVi = True
VIid = myRow.Item("VillageID")
Else
isExistsVi = False
End If
sqlCon.Close()
pGNe is Parameter
VillageSin is a Column and contain UNICODE Data
When compile following error erised
"These Columns dont' Currently have unique values"
How can search unicode data from Dataset
How to correct above c
It seems like this line
myDSGN.Tables("Villages").PrimaryKey = myPrimaryKey
is the one with the error "These Columns dont' Currently have unique values" because your data is running afoul of the unique requirement on primary keys.
All this means is that you can't use Find. This has nothing to do with SQL Server or Unicode data.
instead get rid of this line myDSGN.Tables("Villages").PrimaryKey = myPrimaryKey and use .Select instead

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