SQL Server (ODBC) Guide

SQLAPI++ allows to seamlessly work with a variety of SQL database servers. It provides unified API to access any database, keeping your code portable. But each server has some specific features which a developer has to know in order to leverage server's unique features and avoid potential errors.

For complete information on using SQLAPI++ check out Getting Started and Documentation. This guide covers specific information related to working with SQL Server (ODBC) server using SQLAPI++ library in the following areas:

Connecting to a database

To connect to a database you need to initialize a connection object. A connection object is represented by SAConnection class.

Default API
Starting from version 4.0.3 SQLAPI++ library uses ODBC as default API when working with SQL Server. It means that the library sets the default value of UseAPI connection option as "ODBC". If the library cannot find ODBC interface it throws an exception.
Minimum Version
SQLAPI++ library requires SQLServer ODBC version 2000.x or SQL Server Native Client (ODBC API) version 2005 and higher.

After the connection is created you need to call SAConnection::Connect method to establish connection with SQL Server server:

void Connect(
    const SAString &sDBString,
    const SAString &sUserID, 
    const SAString &sPassword, 
    SAClient_t eSAClient = SA_Client_NotSpecified);
Parameters

sDBString

Connection string in the following format:
[<server_name>@][<database_name>][;<driver_connection_option_list>]
  • <server_name> - connects to a specified server. If it's omitted SQLAPI++ tries to connect to default local server instance
  • <database_name> - connects to a database with the specified name. If it's omitted SQLAPI++ tries to connect to default database
  • <driver_connection_option_list> - SQL Server Native ODBC driver specific option list

To connect to a named instance of SQL Server use <server name\instance name> instead of <server_name> (use double back slash in C++ constants, for example "MyServer\\SQLEXPRESS@pubs").

Since SQLNCLI (SQL Server 2005) also available protocol specific server name part of the connection string:
  • lpc:<servername>[\instancename] - using shared memory
  • tcp:<servername>[\<instancename>],<port> or tcp:<IPAddress>[\<instancename>],<port> - using TCP/IP
  • np:\<computer_name>\pipe\<pipename> or np:\<IPAddress>\pipe\<pipename> - using named pipes
  • via:<servername>[\instancename],<nic_number>:<port> - using VIA

sUserID

A string containing a user name to use when establishing the connection.

If sUserID parameter is empty, SQLAPI++ library requests a secure, or trusted, connection to SQL Server.

sPassword

A string containing a password to use when establishing the connection.

eSAClient

Optional. One of the following values from SAClient_t enum:
  • SA_SQLServer_Client SQL Server client
  • SA_Client_NotSpecified – used by default if eSAClient parameter is omitted. You can use this default value only if you have SAConnection::setAPI method with SAPI object initialized with SA_SQLServer_Client constant before

For more details see Getting Started - Connect to Database, SAConnection object, SAConnection::Connect.

Transaction isolation levels

SQL-92 defines four isolation levels, all of which are supported by SQLAPI++:

  • Read uncommitted (the lowest level where transactions are isolated just enough to ensure that physically corrupt data is not read)
  • Read committed
  • Repeatable read
  • Serializable (the highest level, where transactions are completely isolated from one another)

SQLAPI++ maps different isolation levels on SQL Server (ODBC) in the following way:

SA_ReadUncommittedSQL_TXN_READ_UNCOMMITTED
SA_ReadCommittedSQL_TXN_READ_COMMITTED
SA_RepeatableReadSQL_TXN_REPEATABLE_READ
SA_SerializableSQL_TXN_SERIALIZABLE

In addition to the SQL-92 levels, if you specify 'snapshot' isolation level, it will be mapped as: SA_Snapshot SQL_TXN_SS_SNAPSHOT.

For more details see SAConnection::setIsolationLevel.

Working with Long or Lob (CLob, BLob) data

When fetching data SQLAPI++ detects data types of the columns in the result set and maps those types to internal library types. The mapping determines which native APIs the library will use for fetching LOB data.

The table below shows how SQLAPI++ maps SQL Server server data types to Long/Lob library types:

imageSA_dtLongBinary
textSA_dtLongChar
varbinary(max)SA_dtBLob
[n]varchar(max)SA_dtCLob

When binding input data from your program the reverse mapping is taking place. The SQLAPI++ data type you use for input markers determines what native API program types will be used for sending Long/Lob data to the server.

The table below shows how SQLAPI++ maps its internal library types to SQL Server (ODBC) API data types:
SA_dtLongBinarySQL_LONGVARBINARY
SA_dtLongCharSQL_LONGVARCHAR
SA_dtBLobSQL_VARBINARY
SA_dtCLobSQL_VARCHAR

For additional information see Getting Started - Handle Long/CLob/BLob.

Returning output parameters

SQL Server stored procedures can have integer return codes and output parameters. The return codes and output parameters are sent in the last packet from the server and are therefore not available to the application until all result sets from stored procedure (if any) are completely processed using SACommand::FetchNext method.

Useful Article
There is a good article from Microsoft about dealing with SQL server return values and output parameters: http://msdn.microsoft.com/en-us/library/ms971497.aspx

SQLAPI++ library automatically creates SAParam object to represent function return value. You can refer to this SAParam object using SQLAPI++ predefined name "RETURN_VALUE".

SQLAPI++ library may have difficulties with output [n]varchar(max) and varbinary(max) parameters because they are not supported by some specific ODBC API versions.

For additional information see SACommand::Execute, SAParam object, Getting Started - Get Output Parameters.

Cancelling queries

Using SACommand::Cancel method you can cancel the following types of processing on a statement:

  • function running asynchronously on the statement
  • function running on the statement on another thread

SQLAPI++ calls SQLCancel function to cancel a query. To get more details see SQLCancel function description in native SQL Server (ODBC) documentation.

For additional information see SACommand::Cancel.

Connection, command, parameter and field options

Server specific options can be applied at the API, connection, command, parameter or field levels.

We recommend you specify each option at the appropriate level, although it is possible to specify them at the parent object level as well. In that case the option affects all the child objects.

API level options must be specified in SAPI object. If an internal SAPI object is used for the DBMS API initialization (implicit DBMS API initialization, see SAConnection::Connect method) the related DBMS specific options are taken from the initial connection object.

Connection level options may be specified in either SAPI object or SAConnection object. If specified in SAPI object an option affects all connections on that API.

Command level options may be specified in SAPI object, SAConnection object or SACommand object. If specified in a parent object an option affects all commands on that SAPI or SAConnection object.

Parameter level options may be specified in SAPI object, SAConnection object, SACommand object or SAParam object. If specified in a parent object an option affects all parameters on that SAPI, SAConnection or SACommand object.

Field related options may be specified in SAPI object, SAConnection object, SACommand object or SAField object. If specified in a parent object an option affects all fields on that SAPI , SAConnection or SACommand object.

Specific options applicable to SQL Server (ODBC):

UseAPI
Api Scope
Forces SQLAPI++ library to use ODBC or OLE DB API.
Valid values: "OLEDB", "ODBC"
Default value: "ODBC". SQLAPI++ uses ODBC as the default API
SQLNCLI.LIBS
Api Scope
Specifies SQL Server Native client library list. SQLAPI++ tries to load libraries from this list one by one for loading SQL Server Native API.
Valid values: Any valid SQL Server ODBC/SQLNCLI library name list. Names separated by ';' on Windows or ':' on other OS.
Default value:
  • Windows -"msodbcsql17.dll;msodbcsql13.dll;msodbcsql11.dll;sqlncli11.dll;sqlncli10.dll;sqlncli.dll;sqlsrv32.dll"
  • Linux - "libmsodbcsql-17.so:libmsodbcsql.so"
SQL_COPT_SS_PRESERVE_CURSORS
Connection Scope
When "SQL_PC_ON" value defined the option allows to use the result set after the commit or rollback command called for the current transaction.
Valid values: "SQL_PC_ON"
Default value: none
SQL_COPT_SS_ACCESS_TOKEN
Connection Scope
Specifies the access token used to authenticate to Azure Active Directory. See SQL Server documentation for more information.
Valid values: The string like "eyJ0eXAiOi..." - in the format extracted from an OAuth JSON response
Default value: none
PreFetchRows
Command Scope
Forces SQLAPI++ library to fetch rows in bulk, rather than retrieving records one by one.
Valid values: String containing number of rows in the fetch buffer
Default value: "1"
UseDynamicCursor
Scrollable
Command Scope
Forces SQLAPI++ to use scrollable dynamic server side cursor.
Valid values: "True", "1"
Default value: "False"
SetCursorName
Command Scope
Allows to define the cursor name SQLAPI++ uses for the server side cursor.
Valid values: See SQLSetCursorName documentation
Default value: none
ExecDirect
Command Scope
Forces SQLAPI++ to use SQLExecDirect instead of SQLExecute API function.
Valid values: "True", "1"
Default value: "False"
SQL_ATTR_CONCURRENCY
Command Scope
Sets the statement concurrency attribute. See SQL Server documentation for additional information.
Valid values: "SQL_CONCUR_READONLY", "SQL_CONCUR_VALUES", "SQL_CONCUR_ROWVER", "SQL_CONCUR_LOCK"
SQL_ATTR_CURSOR_TYPE
Command Scope
Sets the statement cursor type. See SQL Server documentation for an additional information.
Valid values: "SQL_CURSOR_FORWARD_ONLY", "SQL_CURSOR_KEYSET_DRIVEN", "SQL_CURSOR_DYNAMIC", "SQL_CURSOR_STATIC"
SQL_ATTR_CURSOR_SCROLLABLE
Command Scope
Sets the statement cursor scrollable. See SQL Server documentation for an additional information.
Valid values: "SQL_NONSCROLLABLE", "SQL_SCROLLABLE"
SQL_ATTR_CURSOR_SENSITIVITY
Command Scope
Sets the statement cursor sensitivity. See SQL Server documentation for an additional information.
Valid values: "SQL_UNSPECIFIED", "SQL_INSENSITIVE", "SQL_SENSITIVE"
SQL_ATTR_QUERY_TIMEOUT
Command Scope
Sets the integer value corresponding to the number of seconds to wait for an SQL statement to execute before returning to the application.
Valid values: String that represents an integer value in seconds
Default value: none

For additional information see SAOptions::setOption.

Using native SQL Server (ODBC) API

You can call client specific API functions which are not directly supported by SQLAPI++ library. SAConnection::NativeAPI method returns a pointer to the set of native API functions available for SQL Server. To use the database API directly you have to downcast this IsaAPI pointer to the appropriate type and use its implementation-specific members. The following example shows what type cast you have to make and what additional header file you have to include to work with SQL Server (ODBC) API. Note that using appropriate type casting depends on an API (that generally mean that you have to explicitly check client version before casting, see SAConnection::ClientVersion method).

To use native API you need to add SQL Server (ODBC) specific #include and cast the result of SAConnection::NativeAPI to class ssNCliAPI:

#include "ssNcliAPI.h"

IsaAPI *pApi = con.NativeAPI();
ssNCliAPI *pNativeAPI = (ssNCliAPI *)pApi;

To get more information about SQL Server API functions see SQL Server (ODBC) documentation.

For additional information see SAConnection::NativeAPI.

Getting native SQL Server (ODBC) connection related handles

You have to use native API handles when you want to call specific SQL Server (ODBC) API functions which are not directly supported by the library. API functions usually need to receive one or more active handles as parameters. SAConnection::NativeHandles method returns a pointer to the set of native API connection related handles. To use API handles directly you have to downcast saConnectionHandles pointer to the appropriate type and use its implementation-specific members.

To access native connection handles you need to add SQL Server (ODBC) specific #include and cast the result to class ssNCliConnectionHandles:

#include "ssNcliAPI.h"

saConnectionHandles *pHandles = con.NativeHandles();
ssNCliConnectionHandles *pNativeHandles = (ssNCliConnectionHandles*)pHandles;

To get more information about SQL Server API functions and handles see SQL Server (ODBC) specific documentation.

For additional information see SAConnection::NativeHandles.

Getting native SQL Server (ODBC) command related handles

You have to use native API handles when you want to call specific SQL Server (ODBC) API functions which are not directly supported by the library. API functions usually need to receive one or more active handles as parameters. SACommand::NativeHandles method returns a pointer to the set of native API command related handles. To use API handles directly you have to downcast saCommandHandles pointer to the appropriate type and use its implementation-specific members.

To access native command handles you need to add SQL Server (ODBC) specific #include and cast the result to class ssNCliCommandHandles:

#include "ssNcliAPI.h"

saCommandHandles *pHandles = cmd.NativeHandles();
ssNCliCommandHandles *pNativeHandles = (ssNCliCommandHandles*)pHandles;

To get more information about SQL Server API functions and handles see SQL Server (ODBC) specific documentation.

For additional information see SACommand::NativeHandles.

Error handling

When an error occurs when executing a SQL statement SQLAPI++ library throws an exception of type SAException and SAException::ErrPos method returns error position in the SQL statement.

In SQL Server (ODBC) API SAException::ErrPos method returns the number of the line within SQL statement where the error occurred.

For additional information see Getting Started - Error Handling, SAException object.