如何使用 SqlCommand 创建带有参数化数据库名称的数据库？

Question

简而言之。我有两个简单的助手：

    private SqlCommand CreateCommand(string text)
    {
        SqlCommand cmd = new SqlCommand();
        cmd.Connection = connection;
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = text;
        return cmd;
    }

    void SetParameter(SqlCommand cmd, string p, string dbName)
    {
        cmd.Parameters.Add(p, SqlDbType.NVarChar);
        cmd.Parameters[p].Value = dbName;
    }

这个执行正常：

var cmd = CreateCommand("CREATE DATABASE Demo "+
            @"ON (FILENAME = N'c:\demo_data.mdf') "+ 
            @"LOG ON (FILENAME = N'c:\demo_data.mdf.LDF') "+
            "FOR ATTACH " +
            "GO");
cmd.ExecuteNonQuery();

但是这个不行：

string dataBaseAttachText = "CREATE DATABASE @dbname " +
                              "ON (FILENAME = @filename) " +
                              "LOG ON (FILENAME = @filenamelog) " +
                              "FOR ATTACH GO";
var cmd = CreateCommand(dataBaseAttachText);

SetParameter(cmd, "@dbname", "Demo");
SetParameter(cmd, "@filename", @"c:\demo_data.mdf");
SetParameter(cmd, "@filenamelog", @"c:\demo_data.mdf.LDF");

cmd.ExecuteNonQuery();

为什么？

Answer 1

DML 操作支持参数，但 DDL 操作不支持参数，DDL 操作没有执行计划。您将需要使用动态 SQL

DDL = 数据定义语言（创建、删除、更改...）

DML = 数据操作语言（选择、更新、删除、插入）

Answer 2

遗憾的是，您可以通过将 DDL 操作包装在 DML 操作中来实现此目的。

var createDatabaseQuery = "exec ('CREATE DATABASE ' + @databaseName)";

var sqlCommand = new SqlCommand(createDatabaseQuery, sqlConnection);
sqlCommand.Parameters.Add("@databaseName", SqlDbType.Text);
sqlCommand.Parameters["@databaseName"].Value = "HelloWorld";

sqlCommand.ExecuteNonQuery();

Answer 3

您只能在 SQL Server 支持的地方使用参数。不幸的是，SQL Server 不支持参数化的CREATE DATABASE 语句（尽管我感觉文件名部分可能支持参数）。

您需要自己构建 SQL：

string dataBaseAttachText = "CREATE DATABASE [" + dbName + "] " + 
                              "ON (FILENAME = @filename) " + 
                              "LOG ON (FILENAME = @filenamelog) " + 
                              "FOR ATTACH GO"; 
var cmd = CreateCommand(dataBaseAttachText); 

SetParameter(cmd, "@filename", @"c:\demo_data.mdf"); 
SetParameter(cmd, "@filenamelog", @"c:\demo_data.mdf.LDF"); 

cmd.ExecuteNonQuery(); 

注意：这很容易受到 SQL 注入攻击，因此必须小心；如果您不信任数据库名称的来源，请不要这样做！

如果文件名部分也无法参数化，则需要对这些部分进行类似的更改。

Answer 4

作为丹尼尔和里奇答案的结合。通过运行 DML 查询 sp_executesql您也可以使用 QUOTENAME 它应该逃避任何可能传入的 sql 注入尝试。

string dataBaseAttachText = @"
DECLARE @SQLString nvarchar(500);
DECLARE @ParmDefinition nvarchar(500);
SET @SQLString =
     N'CREATE DATABASE ' + QUOTENAME(@dbName) + N' 
       ON (FILENAME = @filename) 
       LOG ON (FILENAME = @filenamelog) 
       FOR ATTACH GO'
SET @ParmDefinition = N'@filename nvarchar(MAX), @filenamelog nvarchar(MAX)'
EXECUTE sp_executesql @SQLString, @ParmDefinition, @filename = @filename, @filenamelog = @filenamelog";

var cmd = CreateCommand(dataBaseAttachText); 

SetParameter(cmd, "@dbname", "Demo");
SetParameter(cmd, "@filename", @"c:\demo_data.mdf"); 
SetParameter(cmd, "@filenamelog", @"c:\demo_data.ldf"); 

cmd.ExecuteNonQuery(); 

这应该使用传递的正确参数执行以下 DML sql 查询。

CREATE DATABASE [Demo]
       ON (FILENAME = @filename) 
       LOG ON (FILENAME = @filenamelog) 
       FOR ATTACH GO

Answer 5

我通过创建一个扩展方法来适当地包装所有实体来解决这个问题。

    /// <summary>
    /// Quotes the provided string in a sql friendly way using the standard [ and ] characters 
    /// </summary>
    /// <param name="ObjectName">string to quote</param>
    /// <example>
    /// "mytable".QuoteSqlName() would return [mytable] 
    /// "my[complex]table".QuoteSqlName()  would return [my[[complex]]table]
    /// </example>
    /// <returns>quoted string wrapped by quoting characters</returns>
    /// <remarks>For dynamic sql this may need to be called multiple times, one for each level of encapsulation.</remarks>
    public static string QuoteSqlName(this string ObjectName)
    {
        return ObjectName.QuoteSqlName(']');
    }

    /// <summary>
    /// Quotes the provided string in a sql friendly way using the provided character
    /// </summary>
    /// <param name="ObjectName">string to quote</param>
    /// <param name="QuoteCharacter">Character to quote with, use [ or ] for standard sql quoting</param>
    /// <example>
    /// "mytable".QuoteSqlName() would return [mytable] 
    /// "my[complex]table".QuoteSqlName()  would return [my[[complex]]table]
    /// "justin's computer".QuoteSqlName('\'') would return 'justin''s computer'
    /// </example>
    /// <returns>quoted string wrapped by quoting characters</returns>
    public static string QuoteSqlName(this string ObjectName, char QuoteCharacter)
    {
        return ObjectName.QuoteSqlName(QuoteCharacter, false);
    }

    /// <summary>
    /// Quotes the provided string in a sql friendly way using the provided character
    /// </summary>
    /// <param name="ObjectName">string to quote</param>
    /// <param name="QuoteCharacter">Character to quote with, use [ or ] for standard sql quoting</param>
    /// <param name="IsNvarChar">if true and QuoteCharacter is ' will prefix the quote with N e.g. N'mytable' vs 'mytable'</param>
    /// <example>
    /// "mytable".QuoteSqlName() would return [mytable] 
    /// "my[complex]table".QuoteSqlName()  would return [my[[complex]]table]
    /// "justin's computer".QuoteSqlName('\'') would return 'justin''s computer'
    /// "mytable".QuoteSqlName('\'',false) would reutrn 'mytable'
    /// "mytable".QuoteSqlName('[',true) would return [mytable]
    /// "mytable".QuoteSqlName('\'',true) would reutrn N'mytable'
    /// </example>
    /// <returns>quoted string wrapped by quoting characters</returns>
    public static string QuoteSqlName(this string ObjectName, char QuoteCharacter, bool IsNvarChar)
    {
        if (string.IsNullOrEmpty(ObjectName))
            return ObjectName;

        char OtherQuoteCharacter = (char)0;
        bool UseOtherChar = false;
        if (QuoteCharacter == ']' || QuoteCharacter == '[')
        {
            QuoteCharacter = '[';
            OtherQuoteCharacter = ']';
            UseOtherChar = true;
        }

        var sb = new StringBuilder((int)(ObjectName.Length * 1.5) + 2);
        if (QuoteCharacter == '\'' && IsNvarChar)
            sb.Append('N');

        sb.Append(QuoteCharacter); // start with initial quote character
        for (var i = 0; i < ObjectName.Length; i++)
        {
            sb.Append(ObjectName[i]);
            // if its a quote character, add it again e.g. ] becomes ]]
            if (ObjectName[i] == QuoteCharacter || UseOtherChar && ObjectName[i] == OtherQuoteCharacter)
                sb.Append(ObjectName[i]);
        }
        sb.Append(UseOtherChar ? OtherQuoteCharacter : QuoteCharacter); // finish with other final quote character

        return sb.ToString();
    }

用法：

var QuotedDBName = this.DBName.QuoteSqlName();
CreateDBQuery.AppendFormat("USE {0};", QuotedDBName);
CreateDBQuery.AppendFormat("IF TYPE_ID({0}) IS NULL", DBType.Name.QuoteSqlName('\'', true));
CreateDBQuery.AppendFormat("    CREATE TYPE {0} as {1};", DBType.Name.QuoteSqlName(), DBType.Value);

Answer 6

我通过调用存储过程“sp_executesql”中的构建来解决此任务。
用于创建数据库的连接字符串指向“master”。
完整的SQL语句是参数值的一部分：

using (SqlConnection connection = new SqlConnection(ConnectionString))
{
    using (SqlCommand command = new SqlCommand("sp_executesql", connection))
    {
        command.CommandType = CommandType.StoredProcedure;
        var sql = $"CREATE DATABASE NewDatabaseName";
        command.Parameters.Add("MyParameterName", SqlDbType.NVarChar).Value = sql;
        connection.Open();
        command.ExecuteNonQuery();
    }
}