When I execute Stored Procedure
SELECT * FROM Users
INNER JOIN BloodBankUser ON Users.UserID = BloodBankUser.UserID
It gives me result fine.
but now on .net side
dt.Rows[0]["Address"].ToString();
this gives me Address of table BloodBankUser
dt.Rows[0]["Users.Address"].ToString();
when I debug this statement it execute error
Column 'Users.Address' does not
belong to table.
How can I get Value of Users.Address
While the first answer would be to change your SQL Query to specify a distinct name for each of your field, it is still possible to retrieve the table name associated with your field.
In this example, I am not filling a DataTable using a DataAdapter, but rather I am using the SqlDataReader.
Be aware that this may fail if you are unable to retrieve the database schema for any reason
When calling ExecuteReader on a SqlCommand, there is an overload that allows you to specify a CommandBehavior. In our case, the behavior that we want is CommandBehavior.KeyInfo.
var reader = command.ExecuteReader(CommandBehavior.KeyInfo);
Now, on the reader, you can invoke the GetSchemaTable method. It returns a DataTable that contains the structure of your query.
var schema = reader.GetSchemaTable();
You can read about that table on MSDN.
Our goal now is to match the field and table against its ordinal position in the column list. Three fields from the schema table are relevant to your interest:
ColumnName
BaseTableName
ColumnOrdinal
You can then create an extension method to do that reading:
public static T Field<T>(this SqlDataReader reader, DataTable schema, string table, string field)
{
// Search for the ordinal that match the table and field name
var row = schema.AsEnumerable().FirstOrDefault(r => r.Field<string>("BaseTableName") == table && r.Field<string>("ColumnName") == field);
var ordinal = row.Field<int>("ColumnOrdinal");
return (T)reader.GetValue(ordinal);
}
You can then call that extension method
using (SqlConnection connection = new SqlConnection("your connection string"))
{
connection.Open();
using (SqlCommand command = new SqlCommand("SELECT * FROM Users INNER JOIN BloodBankUser ON Users.UserID = BloodBankUser.UserID;", connection))
using (var reader = command.ExecuteReader(CommandBehavior.KeyInfo))
{
var schema = reader.GetSchemaTable();
while (reader.Read())
{
Console.WriteLine(reader.Field<string>(schema, "Users", "Address"));
}
}
}
Rename the FIELD in the output (Select FIELDNAME as NEWNAME)
You specify the column names rather than use SELECT * FROM You will then be able to do the following
Select User.Username,
User.Address as 'UserAddress',
BloodBankUser.Address as 'BloodbankAddress'
FROM Users
INNER JOIN BloodBankUser ON Users.UserID = BloodBankUser.UserID
Avoid the use of * in SELECT queries. Select only the columns you need and name them explicitly to avoid ambiguity,
Insead of SELECT *... specify the columns you want explicitly, and alias those that may duplicate
SELECT Users.Address as UsersAddress
Related
I am not sure if this is possible but I have not been able to come across clear documentation for this use case. I am using F# 4 and the FSharp.Data.SqlClient library to connect to SQL Server 2016. I am wanting to call a stored procedure that returns multiple tables and turn those tables into the corresponding records. In this case the first table is made up of items and the second table is made up of customers.
My instinct is that it should look something like this:
let items, customers = cmd.Execute()
My gut is that items would be an IEnumerable<item> and customers would be an IEnumerable<customer> where item and customer are both Record types. What it appears is happening though is that FSharp.Data.SqlClient is only seeing the first returned table from the stored procedure. I am working on a SQL Server 2016 Developer instance. Here is the T-SQL to setup the example:
create table Item (
ItemID int identity(1, 1) primary key,
ItemName nvarchar(50)
)
go
create table Customer (
CustomerID int identity(1, 1) primary key,
CustomerName nvarchar(50)
)
go
insert into Item (ItemName) values ('A');
insert into Item (ItemName) values ('B');
insert into Item (ItemName) values ('C');
insert into Customer (CustomerName) values ('Gary');
insert into Customer (CustomerName) values ('Sergei');
insert into Customer (CustomerName) values ('Elise');
go
create procedure dbo.ExampleProcedure
as
begin
set nocount on;
select
ItemID,
ItemName
from Item
select
CustomerID,
CustomerName
from Customer
end;
And here is the F# script that I am testing with. It shows what I would like to be able to do but I get a compile error on the last line:
#r "../packages/FSharp.Data.SqlClient.1.8.2/lib/net40/FSharp.Data.SqlClient.dll"
#r "../packages/FSharp.Data.2.3.2/lib/net40/FSharp.Data.dll"
#r "System.Xml.Linq.dll"
open FSharp.Data
[<Literal>]
let connStr =
"Data Source=**connection string**;"
type queryExample = SqlProgrammabilityProvider<connStr>
do
use cmd = new queryExample.dbo.ExampleProcedure(connStr)
let items, customers = cmd.Execute()
I am wanting items to correspond to the first returned table and customers to correspond to the second returned table. The intellisense suggests that FSharp.Data.SqlClient is only seeing the first table. When I hover over cmd.Execute() the popup says "This expression was expected to have type 'a*'b but here has type System.Collections.Generic.IEnumerable<SqlProgrammabilityProvider<...>.dbo.ExampleProcedure.Record>". If I do the following I get access to the Items query in the stored procedure:
// Learn more about F# at http://fsharp.org. See the 'F# Tutorial' project
// for more guidance on F# programming.
#r "../packages/FSharp.Data.SqlClient.1.8.2/lib/net40/FSharp.Data.SqlClient.dll"
#r "../packages/FSharp.Data.2.3.2/lib/net40/FSharp.Data.dll"
#r "System.Xml.Linq.dll"
open FSharp.Data
[<Literal>]
let connStr =
"Data Source=**connection string**;"
type queryExample = SqlProgrammabilityProvider<connStr>
do
use cmd = new queryExample.dbo.ExampleProcedure(connStr)
for item in cmd.Execute() do
printfn "%A" item.ItemID
Is this even possible? Is my approach wrong? I could not find clear documentation on this use case but I thought it would be common enough it would be covered.
Update
Just to clarify what I am trying to achieve I am showing how I solve this in C#. In C# I create a DataSet object and populate it with the results of the Stored Procedure. From there I pick out the individual tables to work with. After extracting the tables I then use LINQ to transform the rows into the corresponding objects. It often looks something like the following:
using System.Data;
using System.Data.SqlClient;
var connStr = "**connection string**"
var sqlConnection = new SqlConnection(connStr );
var sqlCommand = new SqlCommand("ExampleProcedure", sqlConnection);
sqlCommand.CommandType = CommandType.StoredProcedure;
var dataSet = new DataSet();
var adapter = new SqlDataAdapter(sqlCommand);
adapter.Fill(dataSet);
var itemsTable = dataSet.Tables[0];
// Turn the itemsTable into a List<Item> using LINQ here
var customersTable = dataSet.Tables[1];
// Turn the customersTable into List<Customer> using LINQ here
I find this to be overly verbose for such a simple thing as extracting the individual tables but perhaps I am too sensitive to code clutter. I know that F# must have a more elegant and terse way to express this.
I don't know F#, however this is a data access problem.
When a stored procedure returns multiple resultsets, you need to access they in sequence, one by one.
cmd.ExecuteReader() returns an instance of a datareader pointing to the first resultset. You need to process this resultset, may be filling a list with instances of a custom class, than you call the method "NextResult" and you will have access to the next resultset and so on.
A reference for the method "NextResult": https://msdn.microsoft.com/pt-br/library/system.data.sqlclient.sqldatareader.nextresult(v=vs.110).aspx
I am creating a winform application in c#.and using sql database.
I have one table, employee_master, which has columns like Id, name, address and phone no. Id is auto increment and all other datatypes are varchar.
I am using this code to get the next auto increment value:
string s = "select max(id) as Id from Employee_Master";
SqlCommand cmd = new SqlCommand(s, obj.con);
SqlDataReader dr = cmd.ExecuteReader();
dr.Read();
int i = Convert.ToInt16(dr["Id"].ToString());
txtId.Text = (i + 1).ToString();
I am displaying on a textBox.
But when last row from table is deleted, still I get that value which is recently deleted in textbox
How should I get the next autoincrement value?
To get the next auto-increment value from SQLServer :
This will fetch the present auto-increment value.
SELECT IDENT_CURRENT('table_name');
Next auto-increment value.
SELECT IDENT_CURRENT('table_name')+1;
------> This will work even if you add a row and then delete it because IDENT_CURRENT returns the last identity value generated for a specific table in any session and any scope.
try this:
SELECT IDENT_CURRENT('tbl_name') + IDENT_INCR('tbl_name');
If you are using Microsoft SQL Server. Use this statement to get current identity value of table. Then add your seed value which you have specified at time of designing table if you want to get next id.
SELECT IDENT_CURRENT(<TableName>)
As for me, the best answer is:
dbcc checkident(table_name)
You will see two values (probably same)
current identity value , current column value
When you delete a row from the table the next number will stay the same as it doesnt decrement in any way.
So if you have 100 rows and you deleted row 100. You would have 99 rows but the next number is still going to be 101.
select isnull((max(AddressID)+1),1) from AddressDetails
the max(id) will get you maximum number in the list pf employee_master
e.g. id = 10, 20, 100 so max will get you 100
But when you delete the record it must have been not 100
So you still get 100 back
One important reason for me to say this might be the issue because you are not using order by id in your query
For MS SQL 2005 and greater:
Select Cast(IsNULL(last_value,seed_value) As Int) + Cast(increment_value As Int) As NextID
From sys.identity_columns
WHERE NAME = <Table_Name>
Just a thought, if what you wanted was the last auto-number that you inserted on an already open connection try using:
SELECT ##IDENTITY FROM...
from that connection. That's the best way to keep track of what has just happened on a given connection and avoids race conditions w/ other connections. Getting the maximum identity is not generally feasible.
SqlConnection con = new SqlConnection("Data Source=.\SQLEXPRESS;Initial Catalog=databasename;User ID=sa;Password=123");
con.Open();
SqlCommand cmd = new SqlCommand("SELECT TOP(1) UID FROM InvoiceDetails ORDER BY 1 DESC", con);
SqlDataReader reader = cmd.ExecuteReader();
//won't need a while since it will only retrieve one row
while (reader.Read())
{
string data = reader["UID"].ToString();
//txtuniqueno.Text = data;
//here is your data
//cal();
//txtuniqueno.Text = data.ToString();
int i = Int32.Parse(data);
i++;
txtuid.Text = i.ToString();
}
I have formed few temp tables in my query (TSQL) like - #temphold1, #temphold2, #temphold3..... #temphold10. Each temp table has different schema (different columns) each derived by grouping data from different tables with specific conditions. I need to determine a way to carry all these temp tables to the User Interface and display each table seperately. Is there a way I can add all temp tables with specific indexer that i can retrieve at the User Interface.
thanks for any reply.
No, there is no such indexer.
However, SQL Server and ADO.NET support returning multiple result sets by selecting each table in turn.
See this howto on MSDN (How To Handle Multiple Results by Using the DataReader in Visual C# .NET).
So, in your stored procedure:
-- after populating your temp tables:
SELECT * FROM #table1
SELECT * FROM #table2
SELECT * FROM #table3
In essence, after reading the first recordset, you call NextResult() on the DataReader in order to get the results of the next select:
while(dr.Read())
{
// process data from #table1
}
dr.NextResult();
while(dr.Read())
{
// process data from #table2
}
dr.NextResult();
while(dr.Read())
{
// process data from #table3
}
If you're returning results to C#, you can do it with a DataAdapter like this:
using (SqlConnection conn = new SqlConnection("your connection string")) {
SqlParameter[] sqlParams = new SqlParameter[] {
new SqlParameter("#param1",10),
new SqlParameter("#param2","test")
};
conn.Open();
SqlDataAdapter sa = new SqlDataAdapter("spStoredProcName", conn);
sa.SelectCommand.CommandType = CommandType.StoredProcedure;
sa.SelectCommand.Parameters.AddRange(sqlParams);
DataSet ds = new DataSet();
sa.Fill(ds);
//ds.Tables[0] == first table
//ds.Tables[1] == second table
//... etc.
//Do whatever you need to here
}
I am reading the database schema for VistaDB 4.0 database using the standard ADO.NET 'DbConnection.GetSchema' API. I haven't found a way to obtain the 'Identity' setting for a column? The 'Columns' schema collection doesn't seem to have a column for this and I am not aware of any other collection that I should look into.
If it is not possible by querying any of the available collections, do I have to query some system table or view?
Any help would be appreciated.
There are no "sys" tables in VistaDB. There is a [database schema] table that contains most of what you need though.
[database schema]
You can get the identity columns for a database using the database schema table like this:
select * from [database schema] where typeid = 6
Look in the help file for the typeid list and what they mean.
Then once you have the list, you can match it up to the typeid for tables to see what table the identity column came from.
The only catch with the database schema table is that you cannot self reference or join it to itself (design limitation). So if you need to pull and reference from itself you have to do it in two commands, or through a temp table. The help file has an example of how to do this as well.
Alternate Way
You can also find all the identity columns using a VistaDB stored proc:
select * from VistaDBColumnSchema() where is_identity = true
DDA
If you need to find the next value, seed, etc you can also get those through DDA (Direct Data Access) methods.
The Identities property on an IVistaDBTableSchema object is a collection of the identities for that table. That collection can then be walked to pull the individual values.
The identity information included is the Seed, Step, Tablename, and Columnname.
ADO.NET GetSchemaTable Way
And yes, there is still another way. You can call GetSchemaTable on a reader to get some more information about the underlying structure.
using (VistaDBConnection cn = new VistaDBConnection("Data Source=" + dbName))
{
cn.Open();
using (VistaDBCommand cmd = new VistaDBCommand("Select * from simpletable", cn))
{
using (VistaDBDataReader myReader = cmd.ExecuteReader(CommandBehavior.KeyInfo))
{
//Retrieve column schema into a DataTable.
DataTable schemaTable = myReader.GetSchemaTable();
foreach (DataRow myField in schemaTable.Rows)
{
foreach (DataColumn myProperty in schemaTable.Columns)
{
System.Diagnostics.Debug.WriteLine(myProperty.ColumnName + " = " + myField[myProperty].ToString());
}
}
}
}
}
I am using VFPOLEDB driver to read DBF files and I keep getting this error and I am not sure why and how to fix the problem:
The provider could not determine the Decimal value. For example, the row was just created, the default for the Decimal column was not available, and the consumer had not yet set a new Decimal value.
Here is the code. I call this routine to return a DataSet of the DBF file and display the data in a DataGridView.
public DataSet GetDBFData(FileInfo fi, string tbl)
{
using (OleDbConnection conn = new OleDbConnection(
#"Provider=VFPOLEDB.1;Data Source=" + fi.DirectoryName + ";"))
{
conn.Open();
string command = "SELECT * FROM " + tbl;
OleDbDataAdapter da = new OleDbDataAdapter(command, conn);
DataSet ds = new DataSet();
da.Fill(ds);
return ds;
}
}
I found the solution here:
Error reading certain numeric values with VFPOLEDB driver
SELECT CAST(FieldName As NUMERIC(11, 3)) From TableName
I finally solved the problem by getting the table schema and then casting all of non-character fields to varchar in the select statement. Good enough for previewing the contents of the table.
It is a known issue.
Especially, if You need to select all columns, it is much more comfortable:
Select * from some_table
One working solution is to use another provider, for example Microsoft.Jet.OLEDB.4.0.
Example connection string can be found here: http://docs.30c.org/conn/dbf-foxpro.html
If you add a row from your gridview, it doesn't necessarily use a default value, but rather NULLs, so you may need to pre-set your defaults, or set the schema to NOT Allow Nulls.
You could automate through the columns after the query is done and force defaults based on the columns data types, such as
foreach (DataColumn oDC in YourDataSet.Tables[0].Columns)
{
if (oDC.DataType.ToString().Contains("String"))
oDC.DefaultValue = "";
else if (oDC.DataType.ToString().Contains("Int32"))
oDC.DefaultValue = 0;
else if (oDC.DataType.ToString().Contains("DateTime"))
oDC.DefaultValue = DateTime.MinValue;
}
these are just 3 default types, but there could be others like boolean, decimal, float, whatever, just add into the if/else and put whatever "default" values. It MAY help where otherwise "NULL" values are getting injected in when adding new rows.