问题
I have some code of ADO.NET to dynamically detect the database schema, what I need is how to get unique columns constraints and Primary key constraints using the GetSchema method on SqlConnection. This is the code that I have:
conn.Open();
SqlCommand mSqlCommand = new SqlCommand("sp_pkeys", conn);
mSqlCommand.CommandType = CommandType.StoredProcedure;
mSqlCommand.Parameters.Add(
"@table_name", SqlDbType.NVarChar).Value = tableName;
SqlDataReader mReader = mSqlCommand.ExecuteReader(
(CommandBehavior.KeyInfo | CommandBehavior.SchemaOnly));
//ExecuteReader();
DataTable schema = mReader.GetSchemaTable();
mReader.Close();
conn.Close();
回答1:
There is nothing in the call to GetSchemaTable on SqlConnection which will allow you to figure this out.
It might seem that you can, using the IsKey column value, which should return true for anything that contributes to uniquely identifying the record in the table. However, from the documentation for the IsKey column (emphasis mine):
true : The column is one of a set of columns in the rowset that, taken together, uniquely identify the row. The set of columns with IsKey set to true must uniquely identify a row in the rowset. There is no requirement that this set of columns is a minimal set of columns. This set of columns may be generated from a base table primary key, a unique constraint or a unique index.
Because of this, you can't guarantee that it contributes to a primary key per-se.
Now, if all you need is something to uniquely identify the row, then IsKey is fine, as the primary key is not always the way to uniquely identify a row (e.g. you can have natural identifiers with a unique index). Even if you have a primary key and a unique index with other columns, the values across all those columns in combination will always be unique.
However, if you specifically need to look at the columns that make up the primary key, then GetSchemaTable will not give you the information you need. Rather, you can just make a call to the sp_pkeys system stored procedure to find the names of the columns that contribute to making the primary key.
回答2:
In case still anyone needs a solutions i have created a function for this, the Sqlcommand contains the statement you want to get schema information.
Public Shared Function TableFromCommand(ByVal Command As SqlCommand) As DataTable
Dim Cn As SqlConnection = Nothing
Dim Dt As DataTable
Dim Dr As SqlDataReader
Dim Column As DataColumn
Dim Answer As New DataTable
Try
Answer.TableName = "SearchTable"
Cn = New SqlConnection("Your connection string")
Cn.Open()
Command.Connection = Cn
For Each Prm As SqlParameter In Command.Parameters
If Prm.Direction = ParameterDirection.Input _
OrElse Prm.Direction = ParameterDirection.InputOutput Then
Prm.Value = DBNull.Value
End If
Next
Dr = Command.ExecuteReader(CommandBehavior.SchemaOnly Or CommandBehavior.KeyInfo)
Dt = Dr.GetSchemaTable
Dim Keys As New List(Of DataColumn)
Dim ColumnsDic As New SortedDictionary(Of Integer, DataColumn)
For Each Row As DataRow In Dt.Rows
Column = New DataColumn
With Column
.ColumnName = Row("ColumnName").ToString
.DataType = Type.GetType(Row("DataType").ToString)
.AllowDBNull = CBool(Row("AllowDBNull"))
.Unique = CBool(Row("IsUnique"))
.ReadOnly = CBool(Row("IsReadOnly"))
If Type.GetType(Row("DataType").ToString) Is GetType(String) Then
.MaxLength = CInt(Row("ColumnSize"))
End If
If CBool(Row("IsIdentity")) = True Then
.AutoIncrement = True
.AutoIncrementSeed = -1
.AutoIncrementStep = -1
End If
If CBool(Row("IsKey")) = True Then
Keys.Add(Column)
End If
End With
ColumnsDic.Add(CInt(Row("ColumnOrdinal")), Column)
Answer.Columns.Add(Column)
Next
If Keys.Count > 0 Then
Answer.Constraints.Add("PrimaryKey", Keys.ToArray, True)
End If
Catch ex As Exception
MyError.Show(ex)
Finally
If Cn IsNot Nothing AndAlso Not Cn.State = ConnectionState.Closed Then
Cn.Close()
End If
End Try
Return Answer
End Function
回答3:
You can get the primaryKeys, UniqueKeys and ForeignKeys and any other schema listed in the dataTable returned by this command: "connection.GetSchema (" MetaDataCollections ")"
Below a code that returns you the primaryKeys and UniqueKeys (Key name and column name).
Look all documentation Here
public void Dotransfer()
{
var sourceSchema = new TableSchema(SourceConnectionString);
}
public class TableSchema
{
public TableSchema(string connectionString)
{
this.TableList = new List<string>();
this.ColumnList = new List<Columns>();
this.PrimaryKeyList = new List<PrimaryKey>();
this.ForeignKeyList = new List<ForeignKey>();
this.UniqueKeyList = new List<UniqueKey>();
GetDataBaseSchema(connectionString);
}
public List<string> TableList { get; set; }
public List<Columns> ColumnList { get; set; }
public List<PrimaryKey> PrimaryKeyList { get; set; }
public List<UniqueKey> UniqueKeyList { get; set; }
public List<ForeignKey> ForeignKeyList { get; set; }
protected void GetDataBaseSchema(string ConnectionString)
{
using (SqlConnection connection = new SqlConnection(ConnectionString))
{
System.Data.SqlClient.SqlConnectionStringBuilder builder = new System.Data.SqlClient.SqlConnectionStringBuilder();
builder.ConnectionString = ConnectionString;
string server = builder.DataSource;
string database = builder.InitialCatalog;
connection.Open();
DataTable schemaTables = connection.GetSchema("Tables");
foreach (System.Data.DataRow rowTable in schemaTables.Rows)
{
String tableName = rowTable.ItemArray[2].ToString();
this.TableList.Add(tableName);
string[] restrictionsColumns = new string[4];
restrictionsColumns[2] = tableName;
DataTable schemaColumns = connection.GetSchema("Columns", restrictionsColumns);
foreach (System.Data.DataRow rowColumn in schemaColumns.Rows)
{
string ColumnName = rowColumn[3].ToString();
this.ColumnList.Add(new Columns(){TableName= tableName, FieldName = ColumnName});
}
string[] restrictionsPrimaryKey = new string[4];
restrictionsPrimaryKey[2] = tableName;
DataTable schemaPrimaryKey = connection.GetSchema("IndexColumns", restrictionsColumns);
foreach (System.Data.DataRow rowPrimaryKey in schemaPrimaryKey.Rows)
{
string indexName = rowPrimaryKey[2].ToString();
if (indexName.IndexOf("PK_") != -1)
{
this.PrimaryKeyList.Add(new PrimaryKey()
{
TableName = tableName,
FieldName = rowPrimaryKey[6].ToString(),
PrimaryKeyName = indexName
});
}
if (indexName.IndexOf("UQ_") != -1)
{
this.UniqueKeyList.Add(new UniqueKey()
{
TableName = tableName,
FieldName = rowPrimaryKey[6].ToString(),
UniqueKeyName = indexName
});
}
}
string[] restrictionsForeignKeys = new string[4];
restrictionsForeignKeys[2] = tableName;
DataTable schemaForeignKeys = connection.GetSchema("ForeignKeys", restrictionsColumns);
foreach (System.Data.DataRow rowFK in schemaForeignKeys.Rows)
{
this.ForeignKeyList.Add(new ForeignKey()
{
ForeignName = rowFK[2].ToString(),
TableName = tableName,
// FieldName = rowFK[6].ToString() //There is no information
});
}
}
}
}
}
public class Columns
{
public string TableName { get; set; }
public string FieldName { get; set; }
}
public class PrimaryKey
{
public string TableName { get; set; }
public string PrimaryKeyName { get; set; }
public string FieldName { get; set; }
}
public class UniqueKey
{
public string TableName { get; set; }
public string UniqueKeyName { get; set; }
public string FieldName { get; set; }
}
public class ForeignKey
{
public string TableName { get; set; }
public string ForeignName { get; set; }
// public string FieldName { get; set; } //There is no information
}
回答4:
What about calling GetSchema() on your SqlConnection? Using collectionName="IndexColumns" and a list of schema restrictions you can request the information you want using GetSchema().
See:
- GetSchema and Schema Collections
- Schema Restrictions
Once I established the SqlConnection using the database name, the following worked for me:
var connectionString =
string.Format("Server=.\\SQLEXPRESS;Database={0};Trusted_Connection=true", dbName);
using (var sqlConnection = new SqlConnection(connectionString))
{
sqlConnection.Open();
DataTable tables = sqlConnection.GetSchema("Tables");
foreach (DataRow tablesRow in tables.Rows)
{
string tableName = tablesRow["table_name"].ToString();
Console.WriteLine(tableName);
var indexCols = sqlConnection.GetSchema("IndexColumns",
new string[] {dbName, null, tableName, "PK_" + tableName, null});
foreach (DataRow indexColsRow in indexCols.Rows)
Console.WriteLine(" PK: {0}", indexColsRow["column_name"]);
}
}
来源：https://stackoverflow.com/questions/5849701/how-to-get-columns-primary-key-constraints-using-sqlconnection-getschema