I have an SQL query I get from a configuration file, this query usually contains 3-6 joins.
I need to find at run time, based on the result set represented by SqlDataReader, to find the name of the table for each column.
Here are some thing that don't work:
SqlDataReader.GetName returns the column name but not the table name.
SqlDataReader.GetSchemaTable returns a data table with column information - but all the table names are null.
Querying information_schema doesn't help because I need data on the results of the current query (and the column names are not unique - there are columns with the same name in different tables).
I'm using .net 3.5SP1/ C#/ SQL Server 2008 in a console application.
EDIT: I know this is not possible for all cases since a "column" can be combined from multiple tables, a function or even a constant expression - I'm looking for something that works in the simple case.
EDIT 2: Found out why it didn't work - You can use SqlDataReader.GetSchemaTable to get table information but you have to set CommandBehavior to KeyInfo, you do that in the ExecuteReader call:
reader = cmd.ExecuteReader(CommandBehavior.KeyInfo);
You can use SqlDataReader.GetSchemaTable to get table information but you have to set CommandBehavior to KeyInfo, you do that in the ExecuteReader call:
reader = cmd.ExecuteReader(CommandBehavior.KeyInfo);
This unanswered question on stackoverflow uses SqlDataReader.GetSchemaTable to get the table name. Their problem is that it returns the actual table name rather than the alias that the table has. Not sure if this works with your sql but figured I'd let you know just in case.
I don't know if this information is available. In particular, not all columns of a result set come from a table. From a relational point of view, tables and resultsets are the same thing.
reader = cmd.ExecuteReader();
reader.GetSchemaTable().Rows[0]["BaseTableName"];
In general, this is not possible. Consider the following query:
SELECT col1 FROM table1
UNION ALL
SELECT col1 FROM table2
Clearly col1 comes from more than one table.
you can solve it like the following :
DataTable schemaTable = sqlReader.GetSchemaTable();
foreach (DataRow row in schemaTable.Rows)
{
foreach (DataColumn column in schemaTable.Columns)
{
MessageBox.Show (string.Format("{0} = {1}", column.ColumnName, row[column]));
}
}
SqlCeConnection conn = new SqlCeConnection("Data Source = Database1.sdf");
SqlCeCommand query = conn.CreateCommand();
query.CommandText = "myTableName";
query.CommandType = CommandType.TableDirect;
conn.Open();
SqlCeDataReader myreader = query.ExecuteReader(CommandBehavior.KeyInfo);
DataTable myDataTable= myreader.GetSchemaTable();
//thats the code you asked. in the loop
for (int i = 0; i < myDataTable.Rows.Count; i++)
{
listView1.Columns.Add(myDataTable.Rows[i][0].ToString());
}
How to get database name, table name & column name.
Also possible to get Schema name as well. Tested with MS SQL 2016
CommandBehavior.KeyInfo must be indicated
SqlDataReader sqlDataReader = sqlCommand.ExecuteReader(CommandBehavior.KeyInfo);
DataTable dataTable = sqlDataReader.GetSchemaTable();
for (int i = 0; i < dataTable.Rows.Count - 1; i++)
{
string ii =
dataTable.Rows[i]["BaseCatalogName"].ToString() + "\\" +
dataTable.Rows[i]["BaseTableName"].ToString() + "\\" +
dataTable.Rows[i]["ColumnName"].ToString();
}
Related
How do I extract data from a data table in a sql server database, knowing that the table could have different column names/column count depending on the request?
I would usually use a SqlDataAdapter and then do: da.Fill(dt) but this is not an option as I cannot enumerate through a dataTable in a razor view. I wish to reproduce that table in a view using Razor Pages.
Here is an example of what I might normally do, but it involves knowing exactly what the column names will be and how many there will be. What can I put in the while to return all of the table data in a type that is enumerable?:
SqlConnection connectionCalc = new SqlConnection("<connectionString>");
if (connectionCalc.State.Equals(ConnectionState.Closed))
connectionCalc.Open();
using (var command = connectionCalc.CreateCommand())
{
command.CommandText = $#"SELECT * FROM {tableName}";
SqlDataReader reader = command.ExecuteReader();
column = new Dictionary<string, string>();
int FATUidSingle = -999;
while (reader.Read())
{
TableUid.Add(reader[SelectedCalculation + "TABLE_UID"].ToString());
FATUid.Add(Convert.ToInt32(reader["FAT_UID"]));
ScheduledDate.Add(Convert.ToDateTime(reader["SOME_DATE"]));
TableStatusUid.Add(reader[SelectedCalculation + "ST_UID"].ToString());
StartDate.Add(Convert.ToDateTime(reader["ANOTHER_DATE"]));
EndDate.Add(Convert.ToDateTime(reader["OTHER_DATE"]));
Progress.Add(reader["PROGRESS"].ToString());
}
Run a command like this first to get the field names, then you will know which fields to expect. You could use it to build SQL and set ordinals to point to the column you want
SELECT TABLE_NAME, COLUMN_NAME FROM
INFORMATION_SCHEMA.COLUMNS
where table_name = 'EmployeeDetail'
when you make your enumerable list, make a list of 'tuples' of string and object perhaps, where the string is the field name and the object is the value
If you only worry about exact names but you know column sequence and datatype then you could simply rely on index of column from select statement.
E.g
Select * from Orders
Order table might have 3 columns. Id, Name and Price where id is int, Name is string and Price is long.
So you can do:
var id = reader.GetInt32(0);
var name = reader.GetString(1);
var price = reader.GetInt64(2);
I'm trying to find a way to have access to all the values in a row.
The following code returns one cell. If I change select id to select *, I have access to the row but how can I break it apart?
string find_user = "select id from users where userName = '" + un + "'";
using (SqlConnection con = new SqlConnection(cs))
{
using (SqlCommand cmd = new SqlCommand(find_user, con))
{
con.Open();
user_id = cmd.ExecuteScalar().ToString();
/* use to pass the info to all the pages */
Session.Add("u_id", user_id);
}
}
You cannot access additional columns using .ExecuteScalar(), per the docs:
Executes the query, and returns the first column of the first row in the result set returned by the query. Additional columns or rows are ignored.
Although it is not a route that I would recommend, you can iterate through the fields by using an index on a data reader:
SqlDataReader dataReader = cmd.ExecuteReader();
// for the query's result set, this while loop will go through all the records
while (dataReader.Read())
{
// for the current record, this for loop will go through all the fields
for (int i = 0; i < dataReader.FieldCount; i++)
{
var value = dataReader[i]; // do what you need with the data here
}
}
A better approach would be to specify the field names in the SQL query instead of using SELECT *, then get the values from the data reader by the specific field names (not relying on the order of the fields in the DB).
Also, you have a SQL injection vulnerability. You should look up what this means and how to parameterize a query.
I am attempting to update a simple ms access database. I get an Exception on certain tables that, after searching, I found Microsoft Support - Syntax Error. I believe it means that one of the column names uses a reserved word. This seems to be the case, since all the tables update except the ones with "GUID" as one of the column names, a reserved word. This page also states that I should be using a OleDbAdapter and DataSet, which should solve the problem. Unfortunately I cannot change the name of the column. That is beyond my control, so I have to work with what is given me.
I haven't had to do work with databases much, and everything I know I've learned from examples from the internet (probably bad ones at that). So what is the proper way to update a database using OleDbAdapter and dataSet?
I don't think I should be using DataTable or OleDbCommandBuilder, and I believe the solution has something to do with parameters. But my googleing skills are weak.
OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; " +
Data Souce=" + source);
conn.Open();
OleDbAdapter adapter = new OleDbDataAdapter("SELECT * From " + table, conn);
OleDbCommandBuiler cmdBuiler = new OleDbCommandBuilder(adapter);
DataSet = new DatSet();
adapter.InsertCommand = cmdBuilder.GetInertCommand(true); // Is this necessary?
adapter.Fill( dataSet, table);
DataTable dataTable = dataSet.Tables[table]; // Do I need a DataTable?
DataRow row = dataTable.
row [ attribute ] = field; // Do this for all attributes/fields. I think this is wrong.
dataTable.rows.Add(row);
adapter.Update(dataTable); //<--"Syntax error in INSERT INTO statement." Exception
The problem may be that the column names (especially those whose name are reserved words) should be surrounded by square brackets. The OleDbCommandBuilder, when it creates its own InsertCommand, doesn't surround the names with brackets, so a solution is to manually define the OleDbDataAdapter's InsertCommand:
adapter.InsertCommand = new OleDbCommand(String.Format("INSERT INTO {0} ([GUID], [fieldName]) Values (#guid,#fieldName);", table), conn);
Defining parameters for each column and then manually adding the parameter's values;
adapter.InsertCommand.Parameters.Add(new OleDbParameter("#guid",row["GUID"]));
So summing up, for the tables which have a column named "GUID", you should try something like the following:
OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;" +
"Data Souce=" + source);
conn.Open();
OleDbDataAdapter adapter = new OleDbDataAdapter("SELECT * From " + table, conn);
OleDbCommandBuilder cmdBuilder = new OleDbCommandBuilder(adapter);
adapter.InsertCommand = new OleDbCommand(String.Format("INSERT INTO {0} ([GUID], [fieldName]) Values (#guid,#fieldName);", table), conn);
DataTable dataTable = new DataTable(table);
adapter.Fill( dataTable);
DataRow row = dataTable.NewRow();
row [ fieldName ] = fieldValue;
// eg: row [ "GUID" ] = System.Guid.NewGuid().ToString(); // Do this for all attributes/fields.
dataTable.Rows.Add(row);
adapter.InsertCommand.Parameters.Add(new OleDbParameter("#fieldName",row[fieldName]));
// eg: adapter.InsertCommand.Parameters.Add(new OleDbParameter("#guid",row["GUID"]));
adapter.Update(dataTable);
As to problem #1. Try doing a full qualification of the column name i.e. table.columnName (that fixes the problem in MySQL so maybe it does in Access) also, try putting [ ] around the column name.
Select * is usually a poor option to specifying the column names and using aliases. For example use Select Column1 as 'Column1', Column2 as 'Column2' ....
this makes working with your dataset and datatable much easier as you can access the column by its alias instead of by column indexes.
I find that the DataAdapter is much more useful for filling datasets than for actually modifying a database. I recommend something like:
string updateQuery = "Update ..... Where ...."; //do your magic here
OldDbcommand command = new OleDbCommand(updateQuery);
command.Connection = conn;
conn.Open();
con.ExecuteNonQuery();
conn.Close();
You could fill your dataset with the adapter and then do as I just did to execute your update commands on the DB.
A good place to start would be using DataSetDesigner and Typed DataSets to start
try this walk through : http://msdn.microsoft.com/en-us/library/ms171893(v=vs.80).aspx
A good longterm approach is to use Sql Server Express instead, then you'll have a choice of using : Entity Framework, Linq To Sql or Still keep using the DataSetDesigner and Typed DataSets.
I need to be able to determine from the DataTable returned by DbConnection.GetSchema() whether a particular column in a SQL Server table is identity/auto-increment or not. I cannot resort to querying the system tables directly.
Oddly, if I connect to SQL Server via ODBC, the returned datatype for such a column is returned as "int identity" (or "bigint identity", etc.) but if I use the native SQL Server driver, there appears to be no distinction between an "int" column and an "int identity" column. Is there some other way I can deduce that information?
DataTable has Columns property and DataColumn has a property indicating auto-increment:
bool isAutoIncrement = dataTable.Columns[iCol].AutoIncrement
See This StackOverflow thread
The GetSchema() function will not return the info that you want. Nor will examining the DataTable schema properties. You'll have to go to a lower level and that will depend on the DBMS and likely its version.
The member below retrieves all tables with identity columns and then looks to match a specific table passed as an argument. The code can be modified to either return all the tables or the query optimized to look only for the table of interest.
// see: https://stackoverflow.com/questions/87747/how-do-you-determine-what-sql-tables-have-an-identity-column-programatically
private static string GetIdentityColumnName(SqlConnection sqlConnection, Tuple<string, string> table)
{
string columnName = string.Empty;
const string commandString =
"select TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME from INFORMATION_SCHEMA.COLUMNS "
+ "where TABLE_SCHEMA = 'dbo' and COLUMNPROPERTY(object_id(TABLE_NAME), COLUMN_NAME, 'IsIdentity') = 1 "
+ "order by TABLE_NAME";
DataSet dataSet = new DataSet();
SqlDataAdapter sqlDataAdapter = new SqlDataAdapter();
sqlDataAdapter.SelectCommand = new SqlCommand(commandString, sqlConnection);
sqlDataAdapter.Fill(dataSet);
if (dataSet.Tables.Count > 0 && dataSet.Tables[0].Rows.Count > 0)
{
foreach (DataRow row in dataSet.Tables[0].Rows)
{
// compare name first
if (string.Compare(table.Item2, row[1] as string, true) == 0)
{
// if the schema as specified, we need to match it, too
if (string.IsNullOrWhiteSpace(table.Item1) || string.Compare(table.Item1, row[0] as string) == 0)
{
columnName = row[2] as string;
break;
}
}
}
}
return columnName;
}
I have run into the same. As far as I discovered here "An auto increment column is implemented differently depending upon the type of database you are working with. It isn't exposed via GetOleDbSchema.".
I didn't find any other way than #kelloti mentioned. So at the moment I'm fine with this solution because at the moment I need to know if column is .AutoIncrement. I already have the table in memory so I don't need to query the database again.
#pesaak Please convert this answer into a comment now that you should have enough reputation.
I have a DataSet populated from Excel Sheet. I wanted to use SQLBulk Copy to Insert Records in Lead_Hdr table where LeadId is PK.
I am having following error while executing the code below:
The given ColumnMapping does not match up with any column in the
source or destination
string ConStr=ConfigurationManager.ConnectionStrings["ConStr"].ToString();
using (SqlBulkCopy s = new SqlBulkCopy(ConStr,SqlBulkCopyOptions.KeepIdentity))
{
if (MySql.State==ConnectionState.Closed)
{
MySql.Open();
}
s.DestinationTableName = "PCRM_Lead_Hdr";
s.NotifyAfter = 10000;
#region Comment
s.ColumnMappings.Clear();
#region ColumnMapping
s.ColumnMappings.Add("ClientID", "ClientID");
s.ColumnMappings.Add("LeadID", "LeadID");
s.ColumnMappings.Add("Company_Name", "Company_Name");
s.ColumnMappings.Add("Website", "Website");
s.ColumnMappings.Add("EmployeeCount", "EmployeeCount");
s.ColumnMappings.Add("Revenue", "Revenue");
s.ColumnMappings.Add("Address", "Address");
s.ColumnMappings.Add("City", "City");
s.ColumnMappings.Add("State", "State");
s.ColumnMappings.Add("ZipCode", "ZipCode");
s.ColumnMappings.Add("CountryId", "CountryId");
s.ColumnMappings.Add("Phone", "Phone");
s.ColumnMappings.Add("Fax", "Fax");
s.ColumnMappings.Add("TimeZone", "TimeZone");
s.ColumnMappings.Add("SicNo", "SicNo");
s.ColumnMappings.Add("SicDesc", "SicDesc");
s.ColumnMappings.Add("SourceID", "SourceID");
s.ColumnMappings.Add("ResearchAnalysis", "ResearchAnalysis");
s.ColumnMappings.Add("BasketID", "BasketID");
s.ColumnMappings.Add("PipeLineStatusId", "PipeLineStatusId");
s.ColumnMappings.Add("SurveyId", "SurveyId");
s.ColumnMappings.Add("NextCallDate", "NextCallDate");
s.ColumnMappings.Add("CurrentRecStatus", "CurrentRecStatus");
s.ColumnMappings.Add("AssignedUserId", "AssignedUserId");
s.ColumnMappings.Add("AssignedDate", "AssignedDate");
s.ColumnMappings.Add("ToValueAmt", "ToValueAmt");
s.ColumnMappings.Add("Remove", "Remove");
s.ColumnMappings.Add("Release", "Release");
s.ColumnMappings.Add("Insert_Date", "Insert_Date");
s.ColumnMappings.Add("Insert_By", "Insert_By");
s.ColumnMappings.Add("Updated_Date", "Updated_Date");
s.ColumnMappings.Add("Updated_By", "Updated_By");
#endregion
#endregion
s.WriteToServer(sourceTable);
s.Close();
MySql.Close();
}
I've encountered the same problem while copying data from access to SQLSERVER 2005 and i found that the column mappings are case sensitive on both data sources regardless of the databases sensitivity.
Well, is it right? Do the column names exist on both sides?
To be honest, I've never bothered with mappings. I like to keep things simple - I tend to have a staging table that looks like the input on the server, then I SqlBulkCopy into the staging table, and finally run a stored procedure to move the table from the staging table into the actual table; advantages:
no issues with live data corruption if the import fails at any point
I can put a transaction just around the SPROC
I can have the bcp work without logging, safe in the knowledge that the SPROC will be logged
it is simple ;-p (no messing with mappings)
As a final thought - if you are dealing with bulk data, you can get better throughput using IDataReader (since this is a streaming API, where-as DataTable is a buffered API). For example, I tend to hook CSV imports up using CsvReader as the source for a SqlBulkCopy. Alternatively, I have written shims around XmlReader to present each first-level element as a row in an IDataReader - very fast.
The answer by Marc would be my recomendation (on using staging table). This ensures that if your source doesn't change, you'll have fewer issues importing in the future.
However, in my experience, you can check the following issues:
Column names match in source and table
That the column types match
If you think you did this and still no success. You can try the following.
1 - Allow nulls in all columns in your table
2 - comment out all column mappings
3 - rerun adding one column at a time until you find where your issue is
That should bring out the bug
One of the reason is that :SqlBukCOpy is case sensitive . Follow steps:
In that Case first you have to find your column in Source Table by
using "Contain" method in C#.
Once your Destination column matched with source column get index of
that column and give its column name in SqlBukCOpy .
For Example:`
//Get Column from Source table
string sourceTableQuery = "Select top 1 * from sourceTable";
DataTable dtSource=SQLHelper.SqlHelper.ExecuteDataset(transaction, CommandType.Text, sourceTableQuery).Tables[0];// i use sql helper for executing query you can use corde sw
for (int i = 0; i < destinationTable.Columns.Count; i++)
{ //check if destination Column Exists in Source table
if (dtSource.Columns.Contains(destinationTable.Columns[i].ToString()))//contain method is not case sensitive
{
int sourceColumnIndex = dtSource.Columns.IndexOf(destinationTable.Columns[i].ToString());//Once column matched get its index
bulkCopy.ColumnMappings.Add(dtSource.Columns[sourceColumnIndex].ToString(), dtSource.Columns[sourceColumnIndex].ToString());//give coluns name of source table rather then destination table so that it would avoid case sensitivity
}
}
bulkCopy.WriteToServer(destinationTable);
bulkCopy.Close();
I would go with the staging idea, however here is my approach to handling the case sensitive nature. Happy to be critiqued on my linq
using (SqlConnection connection = new SqlConnection(conn_str))
{
connection.Open();
using (SqlBulkCopy bulkCopy = new SqlBulkCopy(connection))
{
bulkCopy.DestinationTableName = string.Format("[{0}].[{1}].[{2}]", targetDatabase, targetSchema, targetTable);
var targetColumsAvailable = GetSchema(conn_str, targetTable).ToArray();
foreach (var column in dt.Columns)
{
if (targetColumsAvailable.Select(x => x.ToUpper()).Contains(column.ToString().ToUpper()))
{
var tc = targetColumsAvailable.Single(x => String.Equals(x, column.ToString(), StringComparison.CurrentCultureIgnoreCase));
bulkCopy.ColumnMappings.Add(column.ToString(), tc);
}
}
// Write from the source to the destination.
bulkCopy.WriteToServer(dt);
bulkCopy.Close();
}
}
and the helper method
private static IEnumerable<string> GetSchema(string connectionString, string tableName)
{
using (SqlConnection connection = new SqlConnection(connectionString))
using (SqlCommand command = connection.CreateCommand())
{
command.CommandText = "sp_Columns";
command.CommandType = CommandType.StoredProcedure;
command.Parameters.Add("#table_name", SqlDbType.NVarChar, 384).Value = tableName;
connection.Open();
using (var reader = command.ExecuteReader())
{
while (reader.Read())
{
yield return (string)reader["column_name"];
}
}
}
}
What I have found is that the columns in the table and the columns in the input must at least match. You can have more columns in the table and the input will still load. If you have less you'll receive the error.
Thought a long time about answering...
Even if column names are case equally, if the data type differs
you get the same error. So check column names and their data type.
P.S.: staging tables are definitive the way to import.