如何使用 SqlConnection.GetSchema() 获取列主键约束

Question

我有一些 ADO.NET 代码来动态检测数据库架构，我需要的是如何使用 SqlConnection 上的 GetSchema 方法获取唯一列约束和主键约束。这是我的代码：

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();

Answer 1

在对GetSchemaTable on SqlConnection 的调用中没有任何内容可以让您弄清楚这一点。

您可能似乎可以使用IsKey 列值，对于有助于唯一标识表中记录的任何内容，它都应该返回true。但是，来自IsKey 列的文档（强调我的）：

true ：该列是一组中的一个 行集中的列，采取 一起，唯一地标识该行。 IsKey 设置为的列集 true 必须唯一标识行 行集。没有要求 这组列是最小的 列集。这组列 可以从基表生成 主键、唯一约束或 唯一索引。

因此，您不能保证它对主键本身有贡献。

现在，如果您只需要唯一标识行的东西，那么IsKey 就可以了，因为主键并不总是唯一标识行的方法（例如，您可以使用具有唯一索引的自然标识符） .即使您有一个主键和一个包含其他列的唯一索引，所有这些列组合起来的值也将始终是唯一的。

但是，如果您特别需要查看构成主键的列，那么GetSchemaTable 不会为您提供所需的信息。相反，您可以调用sp_pkeys 系统存储过程来查找有助于生成主键的列的名称。

Answer 2

如果仍然有人需要解决方案，我为此创建了一个函数，Sqlcommand 包含您要获取架构信息的语句。

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

Answer 3

您可以获得primaryKeys、UniqueKeys和ForeignKeys以及此命令返回的dataTable中列出的任何其他架构："connection.GetSchema (" MetaDataCollections ")"

下面是返回primaryKeys和UniqueKeys（键名和列名）的代码。

查看所有文档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
    }

Answer 4

在 SqlConnection 上调用 GetSchema() 怎么样？使用 collectionName="IndexColumns" 和架构限制列表，您可以使用 GetSchema() 请求所需的信息。

见：

• GetSchema and Schema Collections
• Schema Restrictions

使用数据库名称建立 SqlConnection 后，以下对我有用：

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"]);
    }
}