Skip to content

transact-sql-tsql-differences-sql-server.md

Latest commit

 

History

History
538 lines (387 loc) · 38.5 KB

transact-sql-tsql-differences-sql-server.md

File metadata and controls

538 lines (387 loc) · 38.5 KB
title T-SQL differences between SQL Server & Azure SQL Managed Instance
description This article discusses the Transact-SQL (T-SQL) differences between an Azure SQL Managed Instance and SQL Server.
services sql-database
ms.service sql-database
ms.subservice managed-instance
ms.devlang
ms.topic conceptual
author jovanpop-msft
ms.author jovanpop
ms.reviewer sstein, carlrab, bonova, danil
ms.date 03/11/2020
ms.custom seoapril2019, sqldbrb=1

T-SQL differences between SQL Server & Azure SQL Managed Instance

This article summarizes and explains the differences in syntax and behavior between Azure SQL Managed Instance and SQL Server.

SQL Managed Instance provides high compatibility with the on-premises SQL Server Database Engine, and most features are supported in a SQL Managed Instance.

Migration

There are some PaaS limitations that are introduced in SQL Managed Instance and some behavior changes compared to SQL Server. The differences are divided into the following categories:

Most of these features are architectural constraints and represent service features.

Temporary known issues that are discovered in SQL Managed Instance and will be resolved in the future are described in release notes page.

Availability

Always On Availability Groups

High availability is built into SQL Managed Instance and can't be controlled by users. The following statements aren't supported:

Backup

SQL Managed Instances have automatic backups, so users can create full database COPY_ONLY backups. Differential, log, and file snapshot backups aren't supported.

  • With a SQL Managed Instance, you can back up an instance database only to an Azure Blob storage account:
    • Only BACKUP TO URL is supported.
    • FILE, TAPE, and backup devices aren't supported.
  • Most of the general WITH options are supported.
    • COPY_ONLY is mandatory.
    • FILE_SNAPSHOT isn't supported.
    • Tape options: REWIND, NOREWIND, UNLOAD, and NOUNLOAD aren't supported.
    • Log-specific options: NORECOVERY, STANDBY, and NO_TRUNCATE aren't supported.

Limitations:

  • With a SQL Managed Instance, you can back up an instance database to a backup with up to 32 stripes, which is enough for databases up to 4 TB if backup compression is used.

  • You can't execute BACKUP DATABASE ... WITH COPY_ONLY on a database that's encrypted with service-managed Transparent Data Encryption (TDE). Service-managed TDE forces backups to be encrypted with an internal TDE key. The key can't be exported, so you can't restore the backup. Use automatic backups and point-in-time restore, or use customer-managed (BYOK) TDE instead. You also can disable encryption on the database.

  • The maximum backup stripe size by using the BACKUP command in a SQL Managed Instance is 195 GB, which is the maximum blob size. Increase the number of stripes in the backup command to reduce individual stripe size and stay within this limit.

    [!TIP] To work around this limitation, when you back up a database from either SQL Server in an on-premises environment or in a virtual machine, you can:

    • Back up to DISK instead of backing up to URL.
    • Upload the backup files to Blob storage.
    • Restore into the SQL Managed Instance.

    The Restore command in a SQL Managed Instance supports bigger blob sizes in the backup files because a different blob type is used for storage of the uploaded backup files.

For information about backups using T-SQL, see BACKUP.

Security

Auditing

The key differences between auditing in databases in Azure SQL Database and databases in SQL Server are:

  • With the SQL Managed Instance deployment option in Azure SQL Database, auditing works at the server level. The .xel log files are stored in Azure Blob storage.
  • With the single database and elastic pool deployment options in Azure SQL Database, auditing works at the database level.
  • In SQL Server on-premises or virtual machines, auditing works at the server level. Events are stored on file system or Windows event logs.

XEvent auditing in SQL Managed Instance supports Azure Blob storage targets. File and Windows logs aren't supported.

The key differences in the CREATE AUDIT syntax for auditing to Azure Blob storage are:

  • A new syntax TO URL is provided that you can use to specify the URL of the Azure Blob storage container where the .xel files are placed.
  • The syntax TO FILE isn't supported because a SQL Managed Instance can't access Windows file shares.

For more information, see:

Certificates

A SQL Managed Instance can't access file shares and Windows folders, so the following constraints apply:

  • The CREATE FROM/BACKUP TO file isn't supported for certificates.
  • The CREATE/BACKUP certificate from FILE/ASSEMBLY isn't supported. Private key files can't be used.

See CREATE CERTIFICATE and BACKUP CERTIFICATE.

Workaround: Instead of creating backup of certificate and restoring the backup, get the certificate binary content and private key, store it as .sql file, and create from binary:

CREATE CERTIFICATE  
   FROM BINARY = asn_encoded_certificate
WITH PRIVATE KEY (<private_key_options>)

Credential

Only Azure Key Vault and SHARED ACCESS SIGNATURE identities are supported. Windows users aren't supported.

See CREATE CREDENTIAL and ALTER CREDENTIAL.

Cryptographic providers

A SQL Managed Instance can't access files, so cryptographic providers can't be created:

Logins and users

  • SQL logins created by using FROM CERTIFICATE, FROM ASYMMETRIC KEY, and FROM SID are supported. See CREATE LOGIN.

  • Azure Active Directory (Azure AD) server principals (logins) created with the CREATE LOGIN syntax or the CREATE USER FROM LOGIN [Azure AD Login] syntax are supported. These logins are created at the server level.

    Managed instance supports Azure AD database principals with the syntax CREATE USER [AADUser/AAD group] FROM EXTERNAL PROVIDER. This feature is also known as Azure AD contained database users.

  • Windows logins created with the CREATE LOGIN ... FROM WINDOWS syntax aren't supported. Use Azure Active Directory logins and users.

  • The Azure AD user who created the instance has unrestricted admin privileges.

  • Non-administrator Azure AD database-level users can be created by using the CREATE USER ... FROM EXTERNAL PROVIDER syntax. See CREATE USER ... FROM EXTERNAL PROVIDER.

  • Azure AD server principals (logins) support SQL features within one SQL Managed Instance only. Features that require cross-instance interaction, no matter whether they're within the same Azure AD tenant or different tenants, aren't supported for Azure AD users. Examples of such features are:

    • SQL transactional replication.
    • Link server.

  • Setting an Azure AD login mapped to an Azure AD group as the database owner isn't supported.

  • Impersonation of Azure AD server-level principals by using other Azure AD principals is supported, such as the EXECUTE AS clause. EXECUTE AS limitations are:

    • EXECUTE AS USER isn't supported for Azure AD users when the name differs from the login name. An example is when the user is created through the syntax CREATE USER [myAadUser] FROM LOGIN [john@contoso.com] and impersonation is attempted through EXEC AS USER = myAadUser. When you create a USER from an Azure AD server principal (login), specify the user_name as the same login_name from LOGIN.

    • Only the SQL Server-level principals (logins) that are part of the sysadmin role can execute the following operations that target Azure AD principals:

      • EXECUTE AS USER
      • EXECUTE AS LOGIN

  • Database export/import using bacpac files are supported for Azure AD users in SQL Managed Instance using either SSMS V18.4 or later, or SQLPackage.exe.

    • The following configurations are supported using database bacpac file:
      • Export/import a database between different manage instances within the same Azure AD domain.
      • Export a database from SQL Managed Instance and import to SQL Database within the same Azure AD domain.
      • Export a database from SQL Database and import to SQL Managed Instance within the same Azure AD domain.
      • Export a database from SQL Managed Instance and import to SQL Server (version 2012 or later).
        • In this configuration all Azure AD users are created as SQL database principals (users) without logins. The type of users are listed as SQL (visible as SQL_USER in sys.database_principals). Their permissions and roles remain in the SQL Server database metadata and can be used for impersonation. However, they cannot be used to access and log in to the SQL Server using their credentials.

  • Only the server-level principal login, which is created by the SQL Managed Instance provisioning process, members of the server roles, such as securityadmin or sysadmin, or other logins with ALTER ANY LOGIN permission at the server level can create Azure AD server principals (logins) in the master database for SQL Managed Instance.

  • If the login is a SQL principal, only logins that are part of the sysadmin role can use the create command to create logins for an Azure AD account.

  • The Azure AD login must be a member of an Azure AD within the same directory that's used for Azure SQL Database SQL Managed Instance.

  • Azure AD server principals (logins) are visible in Object Explorer starting with SQL Server Management Studio 18.0 preview 5.

  • Overlapping Azure AD server principals (logins) with an Azure AD admin account is allowed. Azure AD server principals (logins) take precedence over the Azure AD admin when you resolve the principal and apply permissions to the SQL Managed Instance.

  • During authentication, the following sequence is applied to resolve the authenticating principal:

    1. If the Azure AD account exists as directly mapped to the Azure AD server principal (login), which is present in sys.server_principals as type "E," grant access and apply permissions of the Azure AD server principal (login).
    2. If the Azure AD account is a member of an Azure AD group that's mapped to the Azure AD server principal (login), which is present in sys.server_principals as type "X," grant access and apply permissions of the Azure AD group login.
    3. If the Azure AD account is a special portal-configured Azure AD admin for SQL Managed Instance, which doesn't exist in SQL Managed Instance system views, apply special fixed permissions of the Azure AD admin for SQL Managed Instance (legacy mode).
    4. If the Azure AD account exists as directly mapped to an Azure AD user in a database, which is present in sys.database_principals as type "E," grant access and apply permissions of the Azure AD database user.
    5. If the Azure AD account is a member of an Azure AD group that's mapped to an Azure AD user in a database, which is present in sys.database_principals as type "X," grant access and apply permissions of the Azure AD group login.
    6. If there's an Azure AD login mapped to either an Azure AD user account or an Azure AD group account, which resolves to the user who's authenticating, all permissions from this Azure AD login are applied.

Service key and service master key

Configuration

Buffer pool extension

Collation

The default instance collation is SQL_Latin1_General_CP1_CI_AS and can be specified as a creation parameter. See Collations.

Compatibility levels

  • Supported compatibility levels are 100, 110, 120, 130, 140 and 150.
  • Compatibility levels below 100 aren't supported.
  • The default compatibility level for new databases is 140. For restored databases, the compatibility level remains unchanged if it was 100 and above.

See ALTER DATABASE Compatibility Level.

Database mirroring

Database mirroring isn't supported.

  • ALTER DATABASE SET PARTNER and SET WITNESS options aren't supported.
  • CREATE ENDPOINT … FOR DATABASE_MIRRORING isn't supported.

For more information, see ALTER DATABASE SET PARTNER and SET WITNESS and CREATE ENDPOINT … FOR DATABASE_MIRRORING.

Database options

  • Multiple log files aren't supported.
  • In-memory objects aren't supported in the General Purpose service tier.
  • There's a limit of 280 files per General Purpose instance, which implies a maximum of 280 files per database. Both data and log files in the General Purpose tier are counted toward this limit. The Business Critical tier supports 32,767 files per database.
  • The database can't contain filegroups that contain filestream data. Restore fails if .bak contains FILESTREAM data.
  • Every file is placed in Azure Blob storage. IO and throughput per file depend on the size of each individual file.

CREATE DATABASE statement

The following limitations apply to CREATE DATABASE:

  • Files and filegroups can't be defined.

  • The CONTAINMENT option isn't supported.

  • WITH options aren't supported.

    [!TIP] As a workaround, use ALTER DATABASE after CREATE DATABASE to set database options to add files or to set containment.

  • The FOR ATTACH option isn't supported.

  • The AS SNAPSHOT OF option isn't supported.

For more information, see CREATE DATABASE.

ALTER DATABASE statement

Some file properties can't be set or changed:

  • A file path can't be specified in the ALTER DATABASE ADD FILE (FILENAME='path') T-SQL statement. Remove FILENAME from the script because a SQL Managed Instance automatically places the files.
  • A file name can't be changed by using the ALTER DATABASE statement.

The following options are set by default and can't be changed:

  • MULTI_USER
  • ENABLE_BROKER ON
  • AUTO_CLOSE OFF

The following options can't be modified:

  • AUTO_CLOSE
  • AUTOMATIC_TUNING(CREATE_INDEX=ON|OFF)
  • AUTOMATIC_TUNING(DROP_INDEX=ON|OFF)
  • DISABLE_BROKER
  • EMERGENCY
  • ENABLE_BROKER
  • FILESTREAM
  • HADR
  • NEW_BROKER
  • OFFLINE
  • PAGE_VERIFY
  • PARTNER
  • READ_ONLY
  • RECOVERY BULK_LOGGED
  • RECOVERY_SIMPLE
  • REMOTE_DATA_ARCHIVE
  • RESTRICTED_USER
  • SINGLE_USER
  • WITNESS

For more information, see ALTER DATABASE.

SQL Server Agent

  • Enabling and disabling SQL Server Agent is currently not supported in SQL Managed Instance. SQL Agent is always running.
  • SQL Server Agent settings are read only. The procedure sp_set_agent_properties isn't supported in SQL Managed Instance.
  • Jobs
    • T-SQL job steps are supported.
    • The following replication jobs are supported:
      • Transaction-log reader
      • Snapshot
      • Distributor
    • SSIS job steps are supported.
    • Other types of job steps aren't currently supported:
      • The merge replication job step isn't supported.
      • Queue Reader isn't supported.
      • Command shell isn't yet supported.
    • SQL Managed Instances can't access external resources, for example, network shares via robocopy.
    • SQL Server Analysis Services aren't supported.
  • Notifications are partially supported.
  • Email notification is supported, although it requires that you configure a Database Mail profile. SQL Server Agent can use only one Database Mail profile, and it must be called AzureManagedInstance_dbmail_profile.
    • Pager isn't supported.
    • NetSend isn't supported.
    • Alerts aren't yet supported.
    • Proxies aren't supported.
  • EventLog isn't supported.

The following SQL Agent features currently aren't supported:

  • Proxies
  • Scheduling jobs on an idle CPU
  • Enabling or disabling an Agent
  • Alerts

For information about SQL Server Agent, see SQL Server Agent.

Tables

The following table types aren't supported:

For information about how to create and alter tables, see CREATE TABLE and ALTER TABLE.

Functionalities

Bulk insert / OPENROWSET

A SQL Managed Instance can't access file shares and Windows folders, so the files must be imported from Azure Blob storage:

  • DATASOURCE is required in the BULK INSERT command while you import files from Azure Blob storage. See BULK INSERT.
  • DATASOURCE is required in the OPENROWSET function when you read the content of a file from Azure Blob storage. See OPENROWSET.
  • OPENROWSET can be used to read data from other Azure SQL single databases, SQL Managed Instances or SQL Server instances. Other sources such as Oracle databases or Excel files are not supported.

CLR

A SQL Managed Instance can't access file shares and Windows folders, so the following constraints apply:

Database Mail (db_mail)

  • sp_send_dbmail cannot send attachments using @file_attachments parameter. Local file system and external shares or Azure Blob Storage are not accessible from this procedure.
  • See the known issues related to @query parameter and authentication.

DBCC

Undocumented DBCC statements that are enabled in SQL Server aren't supported in SQL Managed Instances.

  • Only a limited number of Global Trace flags are supported. Session-level Trace flags aren't supported. See Trace flags.
  • DBCC TRACEOFF and DBCC TRACEON work with the limited number of global trace-flags.
  • DBCC CHECKDB with options REPAIR_ALLOW_DATA_LOSS, REPAIR_FAST, and REPAIR_REBUILD cannot be used because database cannot be set in SINGLE_USER mode - see ALTER DATABASE differences. Potential database corruption is handled by the Azure support team. Contact Azure support if there is any indication of database corruption.

Distributed transactions

MSDTC and elastic transactions currently aren't supported in SQL Managed Instances.

Extended Events

Some Windows-specific targets for Extended Events (XEvents) aren't supported:

  • The etw_classic_sync target isn't supported. Store .xel files in Azure Blob storage. See etw_classic_sync target.
  • The event_file target isn't supported. Store .xel files in Azure Blob storage. See event_file target.

External libraries

In-database R and Python, external libraries aren't yet supported. See SQL Server Machine Learning Services.

Filestream and FileTable

  • Filestream data isn't supported.
  • The database can't contain filegroups with FILESTREAM data.
  • FILETABLE isn't supported.
  • Tables can't have FILESTREAM types.
  • The following functions aren't supported:
    • GetPathLocator()
    • GET_FILESTREAM_TRANSACTION_CONTEXT()
    • PathName()
    • GetFileNamespacePat)
    • FileTableRootPath()

For more information, see FILESTREAM and FileTables.

Full-text Semantic Search

Semantic Search isn't supported.

Linked servers

Linked servers in SQL Managed Instances support a limited number of targets:

  • Supported targets are SQL Managed Instance, SQL Database, and SQL Server instances.
  • Linked servers don't support distributed writable transactions (MS DTC).
  • Targets that aren't supported are files, Analysis Services, and other RDBMS. Try to use native CSV import from Azure Blob Storage using BULK INSERT or OPENROWSET as an alternative for file import.

Operations:

  • Cross-instance write transactions aren't supported.
  • sp_dropserver is supported for dropping a linked server. See sp_dropserver.
  • The OPENROWSET function can be used to execute queries only on SQL Server instances. They can be either managed, on-premises, or in virtual machines. See OPENROWSET.
  • The OPENDATASOURCE function can be used to execute queries only on SQL Server instances. They can be either managed, on-premises, or in virtual machines. Only the SQLNCLI, SQLNCLI11, and SQLOLEDB values are supported as a provider. An example is SELECT * FROM OPENDATASOURCE('SQLNCLI', '...').AdventureWorks2012.HumanResources.Employee. See OPENDATASOURCE.
  • Linked servers cannot be used to read files (Excel, CSV) from the network shares. Try to use BULK INSERT or OPENROWSET that reads CSV files from Azure Blob Storage. Track this requests on SQL Managed Instance Feedback item|

PolyBase

External tables that reference the files in HDFS or Azure Blob storage aren't supported. For information about PolyBase, see PolyBase.

Replication

  • Snapshot and Bi-directional replication types are supported. Merge replication, Peer-to-peer replication, and updatable subscriptions are not supported.
  • Transactional Replication is available for public preview on SQL Managed Instance with some constraints:
    • All types of replication participants (Publisher, Distributor, Pull Subscriber, and Push Subscriber) can be placed on SQL Managed Instances, but the publisher and the distributor must be either both in the cloud or both on-premises.
    • SQL Managed Instances can communicate with the recent versions of SQL Server. See the supported versions matrix for more information.
    • Transactional Replication has some additional networking requirements.

For more information about configuring transactional replication, see the following tutorials:

RESTORE statement

  • Supported syntax:
    • RESTORE DATABASE
    • RESTORE FILELISTONLY ONLY
    • RESTORE HEADER ONLY
    • RESTORE LABELONLY ONLY
    • RESTORE VERIFYONLY ONLY
  • Unsupported syntax:
    • RESTORE LOG ONLY
    • RESTORE REWINDONLY ONLY
  • Source:
    • FROM URL (Azure Blob storage) is the only supported option.
    • FROM DISK/TAPE/backup device isn't supported.
    • Backup sets aren't supported.
  • WITH options aren't supported, such as no DIFFERENTIAL or STATS.
  • ASYNC RESTORE: Restore continues even if the client connection breaks. If your connection is dropped, you can check the sys.dm_operation_status view for the status of a restore operation, and for a CREATE and DROP database. See sys.dm_operation_status.

The following database options are set or overridden and can't be changed later:

  • NEW_BROKER if the broker isn't enabled in the .bak file.
  • ENABLE_BROKER if the broker isn't enabled in the .bak file.
  • AUTO_CLOSE=OFF if a database in the .bak file has AUTO_CLOSE=ON.
  • RECOVERY FULL if a database in the .bak file has SIMPLE or BULK_LOGGED recovery mode.
  • A memory-optimized filegroup is added and called XTP if it wasn't in the source .bak file.
  • Any existing memory-optimized filegroup is renamed to XTP.
  • SINGLE_USER and RESTRICTED_USER options are converted to MULTI_USER.

Limitations:

  • Backups of the corrupted databases might be restored depending on the type of the corruption, but automated backups will not be taken until the corruption is fixed. Make sure that you run DBCC CHECKDB on the source SQL Managed Instance and use backup WITH CHECKSUM in order to prevent this issue.
  • Restore of .BAK file of a database that contains any limitation described in this document (for example, FILESTREAM or FILETABLE objects) cannot be restored on SQL Managed Instance.
  • .BAK files that contain multiple backup sets can't be restored.
  • .BAK files that contain multiple log files can't be restored.
  • Backups that contain databases bigger than 8 TB, active in-memory OLTP objects, or number of files that would exceed 280 files per instance can't be restored on a General Purpose instance.
  • Backups that contain databases bigger than 4 TB or in-memory OLTP objects with the total size larger than the size described in resource limits cannot be restored on Business Critical instance. For information about restore statements, see RESTORE statements.

Important

The same limitations apply to built-in point-in-time restore operation. As an example, General Purpose database greater than 4 TB cannot be restored on Business Critical instance. Business Critical database with In-memory OLTP files or more than 280 files cannot be restored on General Purpose instance.

Service broker

Cross-instance service broker isn't supported:

  • sys.routes: As a prerequisite, you must select the address from sys.routes. The address must be LOCAL on every route. See sys.routes.
  • CREATE ROUTE: You can't use CREATE ROUTE with ADDRESS other than LOCAL. See CREATE ROUTE.
  • ALTER ROUTE: You can't use ALTER ROUTE with ADDRESS other than LOCAL. See ALTER ROUTE.

Stored procedures, functions, and triggers

  • NATIVE_COMPILATION isn't supported in the General Purpose tier.
  • The following sp_configure options aren't supported:
    • allow polybase export
    • allow updates
    • filestream_access_level
    • remote access
    • remote data archive
    • remote proc trans
  • sp_execute_external_scripts isn't supported. See sp_execute_external_scripts.
  • xp_cmdshell isn't supported. See xp_cmdshell.
  • Extended stored procedures aren't supported, which includes sp_addextendedproc and sp_dropextendedproc. See Extended stored procedures.
  • sp_attach_db, sp_attach_single_file_db, and sp_detach_db aren't supported. See sp_attach_db, sp_attach_single_file_db, and sp_detach_db.

System functions and variables

The following variables, functions, and views return different results:

  • SERVERPROPERTY('EngineEdition') returns the value 8. This property uniquely identifies a SQL Managed Instance. See SERVERPROPERTY.
  • SERVERPROPERTY('InstanceName') returns NULL because the concept of instance as it exists for SQL Server doesn't apply to a SQL Managed Instance. See SERVERPROPERTY('InstanceName').
  • @@SERVERNAME returns a full DNS "connectable" name, for example, my-managed-instance.wcus17662feb9ce98.database.windows.net. See @@SERVERNAME.
  • SYS.SERVERS returns a full DNS "connectable" name, such as myinstance.domain.database.windows.net for the properties "name" and "data_source." See SYS.SERVERS.
  • @@SERVICENAME returns NULL because the concept of service as it exists for SQL Server doesn't apply to a SQL Managed Instance. See @@SERVICENAME.
  • SUSER_ID is supported. It returns NULL if the Azure AD login isn't in sys.syslogins. See SUSER_ID.
  • SUSER_SID isn't supported. The wrong data is returned, which is a temporary known issue. See SUSER_SID.

Environment constraints

Subnet

VNET

  • VNet can be deployed using Resource Model - Classic Model for VNet is not supported.
  • After a SQL Managed Instance is created, moving the SQL Managed Instance or VNet to another resource group or subscription is not supported.
  • Some services such as App Service Environments, Logic apps, and SQL Managed Instances (used for Geo-replication, Transactional replication, or via linked servers) cannot access SQL Managed Instances in different regions if their VNets are connected using global peering. You can connect to these resources via ExpressRoute or VNet-to-VNet through VNet Gateways.

TEMPDB

The maximum file size of tempdb can't be greater than 24 GB per core on a General Purpose tier. The maximum tempdb size on a Business Critical tier is limited by the SQL Managed Instance storage size. Tempdb log file size is limited to 120 GB on General Purpose tier. Some queries might return an error if they need more than 24 GB per core in tempdb or if they produce more than 120 GB of log data.

MSDB

The following MSDB schemas in SQL Managed Instance must be owned by their respective predefined roles:

Important

Changing the predefined role names, schema names and schema owners by customers will impact the normal operation of the service. Any changes made to these will be reverted back to the predefined values as soon as detected, or at the next service update at the latest to ensure normal service operation.

Error logs

A SQL Managed Instance places verbose information in error logs. There are many internal system events that are logged in the error log. Use a custom procedure to read error logs that filters out some irrelevant entries. For more information, see SQL Managed Instance – sp_readmierrorlog or SQL Managed Instance extension(preview) for Azure Data Studio.

Next steps