c# - 如果存在则删除 SQL 表/如果不存在则创建(在 C# 中)

Question

我正在尝试创建一个 C# 方法来删​​除表(如果它们存在)，如果它们不存在则创建。

到目前为止，我已经创建了一个 SQL 查询，它正在尝试删除存在的表。

但是我收到这个错误

System.Data.SqlClient.SqlException (0x80131904): Incorrect syntax near the keyword 'NULL'.

这是我的代码

        static void CheckTablesExist()
        {
            try
            {
                // Build connection string
                SqlConnectionStringBuilder builder = new SqlConnectionStringBuilder
                {
                    DataSource = "WIN10-LAP-HJP",
                    UserID = "sa",
                    Password = "Mypassword123",
                    InitialCatalog = "SAPExtract"
                };

                // Connect to SQL
                Console.Write("Connecting to SQL Server ... ");
                using (SqlConnection connection = new SqlConnection(builder.ConnectionString))
                {

                    Console.WriteLine("Done.");
                    Console.WriteLine("Checking If table dbo.FolderInfo");

                    string queryCheckTable = "if object_id(@FolderTable, @FileTable) NOT NULL DROP TABLE dbo.FolderInfo ";

                   // string queryCheckTable = "DROP TABLE IF EXISTS @FolderTable";

                    using (SqlCommand command = new SqlCommand(queryCheckTable, connection))
                    {
                        command.Parameters.Add("@FolderTable", SqlDbType.NVarChar).Value = "dbo.FolderInfo";
                        command.Parameters.Add("@FileTable", SqlDbType.NVarChar).Value = "dbo.FileInfo";

                        connection.Open();

                        var result = command.ExecuteNonQuery();

                        // Check Error


                    }
                }
            }

            catch (SqlException e)
            {
                Console.WriteLine(e.ToString());
            }
        }

Answer 1

您收到语法错误是因为在 NOT NULL 之前缺少 IS 一词。以下 SQL 应该可以工作:

if object_id(@FolderTable, @FileTable) IS NOT NULL DROP TABLE dbo.FolderInfo