Question

我有一个来自mysql的查询，该查询已在最近迁移到DB2的表上运行。

由于下面的行，现在在DB2上查询失败，表示找不到DATEDIFF。我只是因为这不是db2上的有效函数。

在DB2上是否有等效的东西可以保持性能和功能？

SELECT DISTINCT
    LEAST(180, DATEDIFF(curdate(), start_date)) as days
FROM table2
where expire_date > curdate()

Answer 1

我使用DAYS()函数将日期转换为数字序号，然后将它们相减，如下所示：

SELECT DISTINCT
    LEAST(180, DAYS(curdate()) - DAYS(start_date)) as days
FROM table2
where expire_date > curdate()

根据DB2的手册，DAYS()返回：“结果比0001年1月1日的天数多1。”

Answer 2

在Db2 11.1（适用于Linux，Unix和Windows）及更高版本上，这将起作用

private static void DropDatabase(IDbConnection connection)
{
    var databaseName = GetDatabaseName(connection.ConnectionString);
    var str = $@"USE master;
                 ALTER DATABASE [{databaseName}] SET SINGLE_USER WITH ROLLBACK IMMEDIATE;
                 DROP DATABASE [{databaseName}];";

    try
    {
        using (DbCommand command = new SqlConnection(connection.ConnectionString).CreateCommand())
        {
            command.CommandText = str;
            command.CommandType = CommandType.Text;
            command.Connection.Open();
            command.ExecuteNonQuery();
            command.Connection.Close();
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex);
    }
}

System.Data.SqlClient.SqlException (0x80131904): Cannot open database "MyTestDb_8647C" requested by the login. The login failed.
Login failed for user 'MYDOMAIN\MyServiceUser'.
    at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, DbConnectionPool pool, String accessToken, Boolean applyTransientFaultHandling, SqlAuthenticationProviderManager sqlAuthProviderManager)
    at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)
    at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)
    at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
    at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
    at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
    at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
    at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
    at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
    at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry)
    at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
    at System.Data.SqlClient.SqlConnection.Open()
    at [...].Testing.DatabaseTestBase.DropDatabase(IDbConnection connection) in D:\[...]\DatabaseTestBase.cs:line 37

DB2查询中的DATEDIFF

2 个答案: