View Source odbc (odbc v2.15)
Erlang ODBC application
This application provides an Erlang interface to communicate with relational SQL-databases. It is built on top of Microsofts ODBC interface and therefore requires that you have an ODBC driver to the database that you want to connect to.
Note
The functions
first/[1,2],last/[1,2],next/[1,2],prev[1,2]andselect/[3,4]assumes there is a result set associated with the connection to work on. Calling the functionselect_count/[2,3]associates such a result set with the connection. Calling select_count again will remove the current result set association and create a new one. Calling a function which dose not operate on an associated result sets, such assql_query/[2,3], will remove the current result set association.Alas some drivers only support sequential traversal of the result set, e.i. they do not support what in the ODBC world is known as scrollable cursors. This will have the effect that functions such as
first/[1,2],last/[1,2],prev[1,2], etc will return{error, driver_does_not_support_function}
Error Handling
The error handling strategy and possible errors sources are described in the Erlang ODBC User's Guide.
References
[1]: Microsoft ODBC 3.0, Programmer's Reference and SDK Guide
See also http://msdn.microsoft.com/
Summary
Types: Types used in ODBC application
Name of column in the result set.
An explanation of what went wrong. For common errors there will be atom decriptions.
Opaque reference to an ODBC connection as returnded by connect/2.
extended error type with ODBC and native database error codes, as well as the base reason that would have been returned had extended_errors not been enabled.
The number of affected rows for UPDATE, INSERT, or DELETE queries. For other query types the value is driver defined, and hence should be ignored.
Data type used by ODBC, to learn which Erlang data type corresponds to an ODBC data type see the Erlang to ODBC data type mapping in the User's Guide.
A tuple, with the number of elements selected form columns in a database row,
containg the values of the columns such as {value(), value() ... value()}.
Return value for queries that select data from database tabels.
Return value for queries that update database tables.
Erlang data type that corresponds to the ODBC data type being handled.
Functions
Equivalent to commit/3.
Commits or rollbacks a transaction. Needed on connections where automatic commit is turned off.
Opens a connection to the database. The connection is associated with the process that created it and can only be accessed through it. This function may spawn new processes to handle the connection. These processes will terminate if the process that created the connection dies or if you call disconnect/1.
Equivalent to describe_table/3.
Queries the database to find out the ODBC data types of the columns of the table
Table.
Closes a connection to a database. This will also terminate all processes that may have been spawned when the connection was opened. This call will always succeed. If the connection cannot be disconnected gracefully it will be brutally killed. However you may receive an error message as result if you try to disconnect a connection started by another process.
Equivalent to first/2.
Returns the first row of the result set and positions a cursor at this row.
Equivalent to last/2.
Returns the last row of the result set and positions a cursor at this row.
Equivalent to next/2.
Returns the next row of the result set relative the current cursor position and
positions the cursor at this row. If the cursor is positioned at the last row of
the result set when this function is called the returned value will be
{selected, ColNames,[]} e.i. the list of row values is empty indicating that
there is no more data to fetch.
Equivalent to param_query/4.
Executes a parameterized SQL query. For an example see the "Using the Erlang API" in the Erlang ODBC User's Guide.
Equivalent to prev/2.
Returns the previous row of the result set relative the current cursor position and positions the cursor at this row.
Equivalent to select/4.
Selects N consecutive rows of the result set. If Position is next it is
semantically equivalent of calling next/[1,2] N times. If Position is
{relative, Pos}, Pos will be used as an offset from the current cursor
position to determine the first selected row. If Position is
{absolute, Pos}, Pos will be the number of the first row selected. After
this function has returned the cursor is positioned at the last selected row. If
there is less then N rows left of the result set the length of Rows will be
less than N. If the first row to select happens to be beyond the last row of
the result set, the returned value will be {selected, ColNames,[]} e.i. the
list of row values is empty indicating that there is no more data to fetch.
Equivalent to select_count/3.
Executes a SQL SELECT query and associates the result set with the connection. A
cursor is positioned before the first row in the result set and the tuple
{ok, NrRows} is returned.
Equivalent to sql_query/3.
Executes a SQL query or a batch of SQL queries. If it is a SELECT query the
result set is returned, on the format {selected, ColNames, Rows}. For other
query types the tuple {updated, NRows} is returned, and for batched queries,
if the driver supports them, this function can also return a list of result
tuples.
Starts the odbc application. Default type is temporary. See application(3)
Stops the odbc application. See application(3)
Types: Types used in ODBC application
-type col_name() :: string().
Name of column in the result set.
-type common_reason() :: connection_closed | extended_error() | term().
An explanation of what went wrong. For common errors there will be atom decriptions.
-opaque connection_reference()
Opaque reference to an ODBC connection as returnded by connect/2.
extended error type with ODBC and native database error codes, as well as the base reason that would have been returned had extended_errors not been enabled.
-type n_rows() :: integer().
The number of affected rows for UPDATE, INSERT, or DELETE queries. For other query types the value is driver defined, and hence should be ignored.
-type odbc_data_type() :: sql_integer | sql_smallint | sql_tinyint | {sql_decimal, Precision :: integer(), Scale :: integer()} | {sql_numeric, Precision :: integer(), Scale :: integer()} | {sql_char, Size :: integer()} | {sql_wchar, Size :: integer()} | {sql_varchar, Size :: integer()} | {sql_wvarchar, Size :: integer()} | {sql_float, Precision :: integer()} | {sql_wlongvarchar, Size :: integer()} | {sql_float, Precision :: integer()} | sql_real | sql_double | sql_bit | atom().
Data type used by ODBC, to learn which Erlang data type corresponds to an ODBC data type see the Erlang to ODBC data type mapping in the User's Guide.
-type row() :: tuple().
A tuple, with the number of elements selected form columns in a database row,
containg the values of the columns such as {value(), value() ... value()}.
Return value for queries that select data from database tabels.
-type updated() :: {updated, n_rows()}.
Return value for queries that update database tables.
-type value() :: null | term().
Erlang data type that corresponds to the ODBC data type being handled.
Functions
-spec commit(ConnectionReference, CommitMode) -> ok | {error, Reason} when ConnectionReference :: connection_reference(), CommitMode :: commit | rollback, Reason :: not_an_explicit_commit_connection | process_not_owner_of_odbc_connection | common_reason().
Equivalent to commit/3.
-spec commit(ConnectionReference, CommitMode, TimeOut) -> ok | {error, Reason} when ConnectionReference :: connection_reference(), CommitMode :: commit | rollback, TimeOut :: erlang:timeout(), Reason :: not_an_explicit_commit_connection | process_not_owner_of_odbc_connection | common_reason().
Commits or rollbacks a transaction. Needed on connections where automatic commit is turned off.
-spec connect(ConnectionStr, Options) -> {ok, ConnectionReferense} | {error, Reason} when ConnectionStr :: string(), Options :: [{auto_commit, on | off} | {timeout, erlang:timeout()} | {binary_strings, on | off} | {tuple_row, on | off} | {scrollable_cursors, on | off} | {trace_driver, on | off} | {extended_errors, on | off}], ConnectionReferense :: connection_reference(), Reason :: port_program_executable_not_found | common_reason().
Opens a connection to the database. The connection is associated with the process that created it and can only be accessed through it. This function may spawn new processes to handle the connection. These processes will terminate if the process that created the connection dies or if you call disconnect/1.
If automatic commit mode is turned on, each query will be considered as an individual transaction and will be automatically committed after it has been executed. If you want more than one query to be part of the same transaction the automatic commit mode should be turned off. Then you will have to call commit/3 explicitly to end a transaction.
The default timeout is infinity
If the option binary_strings is turned on all strings will be returned as binaries and strings inputted to param_query will be expected to be binaries. The user needs to ensure that the binary is in an encoding that the database expects. By default this option is turned off.
As default result sets are returned as a lists of tuples. The TupleMode option
still exists to keep some degree of backwards compatibility. If the option is
set to off, result sets will be returned as a lists of lists instead of a lists
of tuples.
Scrollable cursors are nice but causes some overhead. For some connections speed might be more important than flexible data access and then you can disable scrollable cursor for a connection, limiting the API but gaining speed.
Note
Turning the scrollable_cursors option off is noted to make old odbc-drivers able to connect that will otherwise fail.
If trace mode is turned on this tells the ODBC driver to write a trace log to the file SQL.LOG that is placed in the current directory of the erlang emulator. This information may be useful if you suspect there might be a bug in the erlang ODBC application, and it might be relevant for you to send this file to our support. Otherwise you will probably not have much use of this.
Note
For more information about the
ConnectStrsee description of the function SQLDriverConnect in [1].
The extended_errors option enables extended ODBC error information when an
operation fails. Rather than returning {error, Reason}, the failing function
will return {error, {ODBCErrorCode, NativeErrorCode, Reason}}. Note that this
information is probably of little use when writing database-independent code,
but can be of assistance in providing more sophisticated error handling when
dealing with a known underlying database.
ODBCErrorCodeis the ODBC error string returned by the ODBC driver.NativeErrorCodeis the numeric error code returned by the underlying database. The possible values and their meanings are dependent on the database being used.Reasonis as per theReasonfield when extended errors are not enabled.
Note
The current implementation spawns a port program written in C that utilizes the actual ODBC driver. There is a default timeout of 5000 msec for this port program to connect to the Erlang ODBC application. This timeout can be changed by setting an application specific environment variable 'port_timeout' with the number of milliseconds for the ODBC application. E.g.: [{odbc, [{port_timeout, 60000}]}] to set it to 60 seconds.
-spec describe_table(ConnectionReference, Table) -> {ok, Description} | {error, Reason} when ConnectionReference :: connection_reference(), Table :: string(), Description :: [{col_name(), odbc_data_type()}], Reason :: process_not_owner_of_odbc_connection | common_reason().
Equivalent to describe_table/3.
-spec describe_table(ConnectionReference, Table, TimeOut) -> {ok, Description} | {error, Reason} when ConnectionReference :: connection_reference(), Table :: string(), TimeOut :: erlang:timeout(), Description :: [{col_name(), odbc_data_type()}], Reason :: process_not_owner_of_odbc_connection | common_reason().
Queries the database to find out the ODBC data types of the columns of the table
Table.
-spec disconnect(ConnectionReferense) -> ok | {error, Reason} when ConnectionReferense :: connection_reference(), Reason :: process_not_owner_of_odbc_connection | extended_error().
Closes a connection to a database. This will also terminate all processes that may have been spawned when the connection was opened. This call will always succeed. If the connection cannot be disconnected gracefully it will be brutally killed. However you may receive an error message as result if you try to disconnect a connection started by another process.
-spec first(ConnectionReference) -> Result | {error, Reason} when ConnectionReference :: connection_reference(), Result :: selected(), Reason :: result_set_does_not_exist | driver_does_not_support_function | scrollable_cursors_disabled | process_not_owner_of_odbc_connection | common_reason().
Equivalent to first/2.
-spec first(ConnectionReference, TimeOut) -> Result | {error, Reason} when ConnectionReference :: connection_reference(), TimeOut :: erlang:timeout(), Result :: selected(), Reason :: result_set_does_not_exist | driver_does_not_support_function | scrollable_cursors_disabled | process_not_owner_of_odbc_connection | common_reason().
Returns the first row of the result set and positions a cursor at this row.
-spec last(ConnectionReference) -> Result | {error, Reason} when ConnectionReference :: connection_reference(), Result :: selected(), Reason :: result_set_does_not_exist | driver_does_not_support_function | scrollable_cursors_disabled | process_not_owner_of_odbc_connection | common_reason().
Equivalent to last/2.
-spec last(ConnectionReference, TimeOut) -> Result | {error, Reason} when ConnectionReference :: connection_reference(), TimeOut :: erlang:timeout(), Result :: selected(), Reason :: result_set_does_not_exist | driver_does_not_support_function | scrollable_cursors_disabled | process_not_owner_of_odbc_connection | common_reason().
Returns the last row of the result set and positions a cursor at this row.
-spec next(ConnectionReference) -> Result | {error, Reason} when ConnectionReference :: connection_reference(), Result :: selected(), Reason :: result_set_does_not_exist | driver_does_not_support_function | scrollable_cursors_disabled | process_not_owner_of_odbc_connection | common_reason().
Equivalent to next/2.
-spec next(ConnectionReference, TimeOut) -> Result | {error, Reason} when ConnectionReference :: connection_reference(), TimeOut :: erlang:timeout(), Result :: selected(), Reason :: result_set_does_not_exist | driver_does_not_support_function | scrollable_cursors_disabled | process_not_owner_of_odbc_connection | common_reason().
Returns the next row of the result set relative the current cursor position and
positions the cursor at this row. If the cursor is positioned at the last row of
the result set when this function is called the returned value will be
{selected, ColNames,[]} e.i. the list of row values is empty indicating that
there is no more data to fetch.
-spec param_query(ConnectionReference, SQLQuery, Params) -> Result | {error, Reason} when ConnectionReference :: connection_reference(), SQLQuery :: string(), Params :: [{odbc_data_type(), [value()]}] | [{odbc_data_type(), in | out | inout, [value()]}], Result :: selected() | updated(), Reason :: driver_does_not_support_function | process_not_owner_of_odbc_connection | common_reason().
Equivalent to param_query/4.
-spec param_query(ConnectionReference, SQLQuery, Params, TimeOut) -> Result | {error, Reason} when ConnectionReference :: connection_reference(), SQLQuery :: string(), Params :: [{odbc_data_type(), [value()]}] | [{odbc_data_type(), in | out | inout, [value()]}], TimeOut :: erlang:timeout(), Result :: selected() | updated(), Reason :: driver_does_not_support_function | process_not_owner_of_odbc_connection | common_reason().
Executes a parameterized SQL query. For an example see the "Using the Erlang API" in the Erlang ODBC User's Guide.
Note
Use the function describe_table/[2,3] to find out which ODBC data type that is expected for each column of that table. If a column has a data type that is described with capital letters, alas it is not currently supported by the param_query function. To learn which Erlang data type corresponds to an ODBC data type see the Erlang to ODBC data type mapping in the User's Guide.
-spec prev(ConnectionReference) -> Result | {error, Reason} when ConnectionReference :: connection_reference(), Result :: selected(), Reason :: result_set_does_not_exist | driver_does_not_support_function | scrollable_cursors_disabled | process_not_owner_of_odbc_connection | common_reason().
Equivalent to prev/2.
-spec prev(ConnectionReference, TimeOut) -> Result | {error, Reason} when ConnectionReference :: connection_reference(), TimeOut :: erlang:timeout(), Result :: selected(), Reason :: result_set_does_not_exist | driver_does_not_support_function | scrollable_cursors_disabled | process_not_owner_of_odbc_connection | common_reason().
Returns the previous row of the result set relative the current cursor position and positions the cursor at this row.
-spec select(ConnectionReference, Position, N) -> Result | {error, Reason} when ConnectionReference :: connection_reference(), Position :: next | {relative, integer()} | {absolute, integer()}, N :: integer(), Result :: selected(), Reason :: result_set_does_not_exist | driver_does_not_support_function | scrollable_cursors_disabled | process_not_owner_of_odbc_connection | common_reason().
Equivalent to select/4.
-spec select(ConnectionReference, Position, N, TimeOut) -> Result | {error, Reason} when ConnectionReference :: connection_reference(), Position :: next | {relative, integer()} | {absolute, integer()}, N :: integer(), TimeOut :: erlang:timeout(), Result :: selected(), Reason :: result_set_does_not_exist | driver_does_not_support_function | scrollable_cursors_disabled | process_not_owner_of_odbc_connection | common_reason().
Selects N consecutive rows of the result set. If Position is next it is
semantically equivalent of calling next/[1,2] N times. If Position is
{relative, Pos}, Pos will be used as an offset from the current cursor
position to determine the first selected row. If Position is
{absolute, Pos}, Pos will be the number of the first row selected. After
this function has returned the cursor is positioned at the last selected row. If
there is less then N rows left of the result set the length of Rows will be
less than N. If the first row to select happens to be beyond the last row of
the result set, the returned value will be {selected, ColNames,[]} e.i. the
list of row values is empty indicating that there is no more data to fetch.
-spec select_count(ConnectionReference, SQLQuery) -> {ok, NrRows} | {error, Reason} when ConnectionReference :: connection_reference(), SQLQuery :: string(), NrRows :: n_rows(), Reason :: process_not_owner_of_odbc_connection | common_reason().
Equivalent to select_count/3.
-spec select_count(ConnectionReference, SQLQuery, TimeOut) -> {ok, NrRows} | {error, Reason} when ConnectionReference :: connection_reference(), SQLQuery :: string(), TimeOut :: erlang:timeout(), NrRows :: n_rows(), Reason :: process_not_owner_of_odbc_connection | common_reason().
Executes a SQL SELECT query and associates the result set with the connection. A
cursor is positioned before the first row in the result set and the tuple
{ok, NrRows} is returned.
Note
Some drivers may not have the information of the number of rows in the result set, then
NrRowswill have the valueundefined.
-spec sql_query(ConnectionReference, SQLQuery) -> Result | {error, Reason} when ConnectionReference :: connection_reference(), SQLQuery :: string(), Result :: updated() | selected(), Reason :: process_not_owner_of_odbc_connection | common_reason().
Equivalent to sql_query/3.
-spec sql_query(ConnectionReference, SQLQuery, TimeOut) -> Result | {error, Reason} when ConnectionReference :: connection_reference(), SQLQuery :: string(), TimeOut :: erlang:timeout(), Result :: updated() | selected(), Reason :: process_not_owner_of_odbc_connection | common_reason().
Executes a SQL query or a batch of SQL queries. If it is a SELECT query the
result set is returned, on the format {selected, ColNames, Rows}. For other
query types the tuple {updated, NRows} is returned, and for batched queries,
if the driver supports them, this function can also return a list of result
tuples.
Note
Some drivers may not have the information of the number of affected rows available and then the return value may be
{updated, undefined}.The list of column names is ordered in the same way as the list of values of a row, e.g. the first
ColNameis associated with the firstValuein aRow.
-spec start() -> ok | {error, Reason} when Reason :: term().
Equivalent to start/1.
-spec start(Type) -> ok | {error, Reason} when Type :: permanent | transient | temporary, Reason :: term().
Starts the odbc application. Default type is temporary. See application(3)
-spec stop() -> ok.
Stops the odbc application. See application(3)