In SQL Server I can use sql:variable:
string sql = "select * from mytable where xml_column.exist('//Tag[text()=sql:variable(\"#value\")]') = 1";
I was trying to find similar way to pass parameter into NpgsqlCommand. This one for example does not fail but also does not return any data:
string sql = "select * from mytable where xmlexists('//Tag[text()=\"#value\"]' PASSING BY REF xml_column) = true";
Is there any way of doing it?
Thanks!
Here is a code snippet:
string connstr = "PORT=5432;DATABASE=mydb;HOST=myhost;USER ID=myuser;PASSWORD=mypassword";
using (NpgsqlConnection connection = new NpgsqlConnection(connstr))
{
connection.Open();
string sql = "select xml_column from mytable where xmlexists('//Tag[text()=\"#value\"]' PASSING BY REF xml_column) = true";
using (var cmd = connection.CreateCommand())
{
cmd.CommandText = sql;
cmd.Parameters.AddWithValue("#value", "my value");
using (var reader = cmd.ExecuteReader())
{
while (reader.Read())
{
reader[0].Dump();
}
}
}
connection.Close();
}
Cross-posted on github, see answer there: https://github.com/npgsql/npgsql/issues/2946
Related
I need to use a variable (edifcodigo) which assigned value is retrieved from one query to insert it in a table by using other query but there is a error that says this variable is not available in actual context. I'm kind of new in aspnet, could anybody know how to figure this out?
This is the code I have:
//Connect to db
string connetionString = #"myconexionstring";
string sql = "SELECT TOP 1 id_proyecto AS codigo FROM DNN_SCO_PROY_CO_PROYECTO_TBL WHERE nombre_proyecto= '"+ uedif +"'";
//find building code by querying the database
try
{
using (SqlConnection conexion = new SqlConnection(connetionString))
{
conexion.Open();
using (SqlCommand query = new SqlCommand(sql, conexion))
{
SqlDataReader result = query.ExecuteReader();
while (result.Read())
{
string edifcodigo = result["codigo"].ToString();
}
}
}
}
catch (Exception ex)
{
Response.Write(ex.Message);
}
//Save referer friend
try
{
using (SqlConnection conn = new SqlConnection(connetionString))
{
conn.Open();
using (SqlCommand cmd = new SqlCommand("DNN_SVI_SCO_DATOS_RECOMIENDA_AMIGO_SP", conn))
{
cmd.CommandType = System.Data.CommandType.StoredProcedure;
cmd.Parameters.Add("#DRA_PROYECTO_CLIENTE", System.Data.SqlDbType.VarChar).Value = edifcodigo; ;
}
}
}
catch (Exception ex)
{
Response.Write(ex.Message);
}
That's because you declared the variable inside a different code block. Every time you open a curly bracket, you open a new code block. Every time you close the curly bracket, you close the current code block. Each code block have it's own scope - it can access variables declared in the surrounding code block, but not variables declared in "sibling" code blocks.
Also, please read about parameterized queries and how they protect you from SQL injection, and change your queries accordingly.
Also, you don't need to close the connection between the two commands, and you can reuse a single command instance in this case. Here is an improved version of your code:
//Connect to db
var connetionString = #"myconexionstring";
var sql = "SELECT TOP 1 id_proyecto AS codigo FROM DNN_SCO_PROY_CO_PROYECTO_TBL WHERE nombre_proyecto = #nombre_proyecto";
//find building code by querying the database
try
{
using (var conexion = new SqlConnection(connetionString))
{
conexion.Open();
using (var cmd = new SqlCommand(sql, conexion))
{
cmd.Parameters.Add("#nombre_proyecto", SqlDbType.NVarChar).Value = uedif;
var edifcodigo = cmd.ExecuteScalar();
//Save referer friend
cmd.Parameters.Clear();
cmd.CommandText = "DNN_SVI_SCO_DATOS_RECOMIENDA_AMIGO_SP";
cmd.CommandType = System.Data.CommandType.StoredProcedure;
cmd.Parameters.Add("#DRA_PROYECTO_CLIENTE", System.Data.SqlDbType.VarChar).Value = edifcodigo; ;
}
}
}
catch (Exception ex)
{
Response.Write(ex.Message);
}
You are declaring the string variable inside your while loop, it loses scope once you exit the while loop, move it's declaration above with:
string connetionString = #"myconexionstring";
string sql = "SELECT TOP 1 id_proyecto AS codigo FROM DNN_SCO_PROY_CO_PROYECTO_TBL WHERE nombre_proyecto= '"+ uedif +"'";
string edifcodigo = "";
You are trying to use a variable that declared in another scope. edifcodigo should be declared in the parent scope of both try blocks.
//Connect to db
string connetionString = #"myconexionstring";
string sql = "SELECT TOP 1 id_proyecto AS codigo FROM DNN_SCO_PROY_CO_PROYECTO_TBL WHERE nombre_proyecto= '"+ uedif +"'";
string edifcodigo=""; // YOU SHOULD DECLARE edifcodigo HERE
and than rest of code will come
//find building code by querying the database
try
{
using (SqlConnection conexion = new SqlConnection(connetionString))
{
conexion.Open();
using (SqlCommand query = new SqlCommand(sql, conexion))
{
SqlDataReader result = query.ExecuteReader();
while (result.Read())
{
edifcodigo = result["codigo"].ToString();
}
}
}
}
catch (Exception ex)
{
Response.Write(ex.Message);
}
//Save referrer friend
try
{
using (SqlConnection conn = new SqlConnection(connetionString))
{
conn.Open();
using (SqlCommand cmd = new SqlCommand("DNN_SVI_SCO_DATOS_RECOMIENDA_AMIGO_SP", conn))
{
cmd.CommandType = System.Data.CommandType.StoredProcedure;
cmd.Parameters.Add("#DRA_PROYECTO_CLIENTE", System.Data.SqlDbType.VarChar).Value = edifcodigo; ;
}
}
}
catch (Exception ex)
{
Response.Write(ex.Message);
}
I'm trying to update a SQLite database with a column "URL" with a specific value. The old url format is "http://www.blz.nl/voster/boek/9789056628512" and the new one is "http://www.blz.nl/voster/boekwinkel/zoeken/?q=9780789327505&oa=true&searchin=taal&taal=dut".
What I am trying to do is replace the url to the new format but keep the value of the 'Q' param from the old url. What is the fastest / best way to achieve this for all columns? I have no idea how to approach this using an SQL query.
You want the SQL?
Basically, you read in the table, search for your keyword, replace it, and write that data back to the database.
Assuming your database name is "mydatabase.db", your code would look something like this (untested):
using Devart.Data.SQLite;
public void Convert()
{
using (var conn = new SQLiteConnection("DataSource=mydatabase.db"))
{
var boek = "//boek//";
var boekwinkel = "//boekwinkel//";
var boek_len = boek.Length;
var table = new DataTable();
var sqlCmd = "SELECT * FROM TableName1;";
conn.Open();
// Read the data into the DataTable:
using (var cmd = new SQLiteCommand(sqlCmd, conn))
{
// The DataTable is ReadOnly!
table.Load(cmd.ExecuteReader());
}
// Use a new SQLiteCommand to write the data.
using (var cmd = new SQLiteCommand("UPDATE TableName1 SET URL=#NEW_URL WHERE URL=#URL;", conn))
{
cmd.Parameters.Add("#URL", SQLiteType.Text, 20);
cmd.Parameters.Add("#NEW_URL", SQLiteType.Text, 20);
foreach (DataRow row in table.Rows)
{
var url = String.Format("{0}", row["URL"]).Trim();
cmd.Parameters["#URL"].SQLiteValue = row["URL"];
if (!String.IsNullOrEmpty(url))
{
var index = url.IndexOf(boek);
if (-1 < index)
{
var first = url.Substring(0, index);
var middle = boekwinkel;
var last = url.Substring(index + boek_len);
var new_url = String.Format("{0}{1}{2}&oa=true&searchin=taal&taal=dut", first, middle, last);
// Place a break point after String.Format.
// Make sure the information being written is correct.
cmd.Parameters["#NEW_URL"].SQLiteValue = new_url;
cmd.ExecuteNonQuery();
}
}
}
}
conn.Close();
}
}
Can someone tell me in a simple way, how can I use an Oracle DB in my ASP.NET MVC 5 project? I have tried different articles but I didn't get a clear answer...
I think this is the simple way to do this:
using System.Data.OracleClient;
public string GetConnectionString()
{
String connString = "SERVER=(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=YourHostName)(PORT=YourPort))(CONNECT_DATA=(SERVICE_NAME=YourServiceName)));uid=YourUserId;pwd=YourPassword;";
return connString;
}
public void ConnectingToOracle()
{
string connectionString = GetConnectionString();
using (OracleConnection connection = new OracleConnection())
{
connection.ConnectionString = connectionString;
connection.Open();
OracleCommand command = connection.CreateCommand();
string sql = "select * from MyDatabase where name like '%John Paul%'";
command.CommandText = sql;
OracleDataReader reader = command.ExecuteReader();
while (reader.Read())
{
string myField = (string)reader["address"]; //Get the address of John Paul
}
}
}
I am having problem when doing retrieve function in 3-tier in C#. Here is the codes:
public DistributionStandardPackingUnits getSPUDetail(string distributionID)
{
DistributionStandardPackingUnits SPUFound = new DistributionStandardPackingUnits();
using (var connection = new SqlConnection(FoodBankDB.connectionString))
{
SqlCommand command = new SqlCommand("SELECT name, description, quantity FROM dbo.DistributionStandardPackingUnits WHERE distribution = '" + distributionID + "'", connection);
connection.Open();
using (var dr = command.ExecuteReader())
{
while (dr.Read())
{
string name = dr["name"].ToString();
string description = dr["description"].ToString();
string quantity = dr["quantity"].ToString();
SPUFound = new DistributionStandardPackingUnits(name, description, quantity);
}
}
}
return SPUFound;
}
When I run in browser, it just won't show up any retrieved data. When I run in debugging mode, I realized that when it hits the while loop, instead of executing the dr.Read(), it simply just skip the entire while loop and return null values. I wonder what problem has caused this. I tested my query using the test query, it returns me something that I wanted so I think the problem does not lies at the Sql statement.
Thanks in advance.
Edited Portion
public static SqlDataReader executeReader(string query)
{
SqlDataReader result = null;
System.Diagnostics.Debug.WriteLine("FoodBankDB executeReader: " + query);
SqlConnection connection = new SqlConnection(connectionString);
SqlCommand command = new SqlCommand(query, connection);
connection.Open();
result = command.ExecuteReader();
connection.Close();
return result;
}
I access data in .dbf files via System.Data.OleDb (vfpoledb.dll). How can I find out whether table exists via SQL command? Something similar to the following on SQL server:
IF (EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'TheTable'))
BEGIN
--Do Stuff
END
If you have a dbc file you can query it to see if the table exists.
string dbc = "northwind.dbc";
using (OleDbConnection conn = new OleDbConnection(connectionString)) {
DataTable dt = new DataTable();
string sql = string.Format(#"SELECT * FROM {0} WHERE ALLTRIM(ObjectType) = 'Table' AND UPPER(ALLTRIM(ObjectName)) = '{1}'", dbc, tableName.ToUpper());
OleDbDataAdapter da = new OleDbDataAdapter(sql, conn);
da.Fill(dt);
bool tableExists = dt != null && dt.Rows.Count == 1;
}
But really you don't need a sql command or a dbc file to get that information. You can get it straight from the OleDbConnection using the GetSchema method.
using (OleDbConnection conn = new OleDbConnection(connectionString)) {
conn.Open();
DataTable tables = conn.GetSchema("Tables");
conn.Close();
var tableExists = (from row in tables.AsEnumerable()
where row.Field<string>("Table_Name").Equals(tableName, StringComparison.CurrentCultureIgnoreCase)
select row.Field<string>("Table_Name")).FirstOrDefault() != null;
}
Additionally, if you are connecting to DBF tables that are "FREE" tables and NOT actually part of a connected "database" (.dbc), then you can just check for the file's existence or not... Such as in C# via
if( File.Exists( PathToTheDatabaseDirectory + TableYouExpect + ".DBF" ))
file is there
else
file is missing
I don't know how to do it only using SQL but maybe you could check for the existence of the file on disk using the File.Exists Method or you could write some code to check for the existence of the dbf using the OleDb classes:
private bool DbfExists(string dbfName, string connectionString)
{
bool dbfExists = true;
using(OleDbConnection conn = new OleDbConnection(connectionString))
{
string sql = string.Format("SELECT * FROM {0}", dbfName);
using(OleDbCommand command = new OleDbCommand(sql, conn))
{
OleDbDataReader reader = null;
try
{
conn.Open();
reader = command.ExecuteReader();
}
catch(Exception ex)
{
dbfExists = false;
}
finally
{
conn.Close();
reader = null;
}
}
}
return dbfExists;
}
I have not tried compiling this code so it may need to be tweaked a bit.