odbc(3erl)

📦
version 25.3.2.8 · 3 versions
, in debian bookworm, ubuntu noble

okay bestie, this is odbc(3erl) — the Erlang Module Definition for the Erlang ODBC application, and we are gonna get you comfy with it 💅✨

🌸 NAME 🌸

odbc — Erlang ODBC application. That's the whole name vibe. 🫶

✨ DESCRIPTION ✨

This application gives you an Erlang interface to talk to relational SQL-databases. It's built on top of Microsoft's ODBC interface, so no cap: you need an ODBC driver for the database you want to connect to, or this whole thing is not gonna slay. 🔥

Note, bestie: first/[1,2], last/[1,2], next/[1,2], prev[1,2] and select/[3,4] assume there is a result set associated with the connection to work on. Calling select_count/[2,3] associates such a result set with the connection. Calling select_count again removes the current result set association and creates a new one. Calling a function which does not operate on an associated result set, such as sql_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}. 😭

🧚 COMMON DATA TYPES 🧚

Here are the type definitions used by more than one function in the ODBC API. They're the shared lore. 💜

Note: The type TimeOut has the default value infinity, so for instance commit(Ref, CommitMode) is the same as commit(Ref, CommitMode, infinity). If the timeout expires the client will exit with the reason timeout. ⏳
connection_reference() - as returned by connect/2

time_out() = milliseconds() | infinity

milliseconds() = integer() >= 0

common_reason() = connection_closed | extended_error() | term() - some kind of
explanation of what went wrong

extended_error() = {string(), integer(), Reason} - 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.

string() = list of ASCII characters

col_name() = string() - Name of column in the result set

col_names() - [col_name()] - e.g. a list of the names of the
          selected columns in the result set.

row() = {value()} - Tuple of column values e.g. one row of the
          result set.

value() = null | term() - A column value.

rows() = [row()] - A list of rows from the result set.

result_tuple() =
     {updated, n_rows()} | {selected, col_names(), rows()}

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.

odbc_data_type() = sql_integer | sql_smallint | sql_tinyint |
     {sql_decimal, precision(), scale()} |
     {sql_numeric, precision(), scale()} |
     {sql_char, size()} |
     {sql_wchar, size()} |
     {sql_varchar, size()} |
     {sql_wvarchar, size()}|
     {sql_float, precision()} |
     {sql_wlongvarchar, size()} |
     {sql_float, precision()} |
     sql_real | sql_double | sql_bit | atom()

precision() = integer()

scale() = integer()

size() = integer()

💀 ERROR HANDLING 💀

The error handling strategy and possible error sources are described in the Erlang ODBC User's Guide. That's the official lore drop. 📚

👑 EXPORTS 👑

💖 commit(Ref, CommitMode) / commit(Ref, CommitMode, TimeOut)

Signature:

commit(Ref, CommitMode) ->
commit(Ref, CommitMode, TimeOut) -> ok | {error, Reason}

Types:

Ref = connection_reference()
CommitMode = commit | rollback
TimeOut = time_out()
Reason = not_an_explicit_commit_connection |
process_not_owner_of_odbc_connection | common_reason()

Commits or rollbacks a transaction. You need this on connections where automatic commit is turned off. Slay the transaction, basically. ✅

💖 connect(ConnectStr, Options)

Signature:

connect(ConnectStr, Options) -> {ok, Ref} | {error, Reason}

Types:

ConnectStr = string()
  An example of a connection string: "DSN=sql-server;UID=aladdin;PWD=sesame"
  where DSN is your ODBC Data Source Name, UID is a database user id and PWD
  is the password for that user. These are usually the attributes required in
  the connection string, but some drivers have other driver specific
  attributes, for example
  "DSN=Oracle8;DBQ=gandalf;UID=aladdin;PWD=sesame"
  where DBQ is your TNSNAMES.ORA entry name e.g. some Oracle specific
  configuration attribute.
Options = [] | [option()]
  All options has default values.
option() = {auto_commit, on | off} | {timeout, milliseconds()}
| {binary_strings, on | off} | {tuple_row, on | off} |
{scrollable_cursors, on | off} | {trace_driver, on | off} |
{extended_errors, on | off}
Ref = connection_reference() - should be used to access the
connection.
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 ConnectStr see 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. 🧠

  • ODBCErrorCode is the ODBC error string returned by the ODBC driver.
  • NativeErrorCode is the numeric error code returned by the underlying database. The possible values and their meanings are dependent on the database being used.
  • Reason is as per the Reason field 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. ⏱️

💖 disconnect(Ref)

Signature:

disconnect(Ref) -> ok | {error, Reason}

Types:

Ref = 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. 💀

💖 describe_table(Ref, Table) / describe_table(Ref, Table, Timeout)

Signature:

describe_table(Ref, Table) ->
describe_table(Ref, Table, Timeout) -> {ok, Description} | {error,
Reason}

Types:

Ref = connection_reference()
Table = string() - Name of database table.
TimeOut = time_out()
Description = [{col_name(), odbc_data_type()}]
Reason = common_reason()

Queries the database to find out the ODBC data types of the columns of the table Table. 🔍

💖 first(Ref) / first(Ref, Timeout)

Signature:

first(Ref) ->
first(Ref, Timeout) -> {selected, ColNames, Rows} | {error, Reason}

Types:

Ref = connection_reference()
TimeOut = time_out()
ColNames = col_names()
Rows = rows()
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. 🥇

💖 last(Ref) / last(Ref, TimeOut)

Signature:

last(Ref) ->
last(Ref, TimeOut) -> {selected, ColNames, Rows} | {error, Reason}

Types:

Ref = connection_reference()
TimeOut = time_out()
ColNames = col_names()
Rows = rows()
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. 🏁

💅 next — next row, please 💅

next(Ref) ->
next(Ref, TimeOut) -> {selected, ColNames, Rows} | {error, Reason}

Types:

  • Ref = connection_reference()
  • TimeOut = time_out()
  • ColNames = col_names()
  • Rows = rows()
  • Reason = result_set_does_not_exist | 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. Slay. 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. No more snacks in the bag, bestie.

🦋 param_query — parameterized-query main character 🦋

param_query(Ref, SQLQuery, Params) ->
param_query(Ref, SQLQuery, Params, TimeOut) -> ResultTuple | {error,
Reason}

Types:

  • Ref = connection_reference()
  • SQLQuery = string() — a SQL query with parameter markers/place holders in form of question marks.
  • Params = [{odbc_data_type(), [value()]}] |[{odbc_data_type(), in_or_out(), [value()]}]
  • in_or_out = in | out | inout Defines IN, OUT, and IN OUT Parameter Modes for stored procedures.
  • TimeOut = time_out()
  • Values = term() — Must be consistent with the Erlang data type that corresponds to the ODBC data type ODBCDataType.

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. Too know which Erlang data type corresponds to an ODBC data type see the Erlang to ODBC data type mapping in the User's Guide.

🎀 prev — we're going back, bestie 🎀

prev(Ref) ->
prev(ConnectionReference, TimeOut) -> {selected, ColNames, Rows} |
{error, Reason}

Types:

  • Ref = connection_reference()
  • TimeOut = time_out()
  • ColNames = col_names()
  • Rows = rows()
  • 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. Rewind era.

✨ start — boot it up ✨

start() ->
start(Type) -> ok | {error, Reason}

Types:

  • Type = permanent | transient | temporary

Starts the odbc application. Default type is temporary. See application(3erl).

🌈 stop — shut it down, gently 🌈

stop() -> ok

Stops the odbc application. See application(3erl).

🔥 sql_query — query or batch, we love range 🔥

sql_query(Ref, SQLQuery) ->
sql_query(Ref, SQLQuery, TimeOut) -> ResultTuple | [ResultTuple]
|{error, Reason}

Types:

  • Ref = connection_reference()
  • SQLQuery = string() — The string may be composed by several SQL-queries separated by a ";", this is called a batch.
  • TimeOut = time_out()
  • ResultTuple = result_tuple()
  • 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 ColName is associated with the first Value in a Row.

💜 select_count — how many rows are we working with? 💜

select_count(Ref, SelectQuery) ->
select_count(Ref, SelectQuery, TimeOut) -> {ok, NrRows} | {error,
Reason}

Types:

  • Ref = connection_reference()
  • SelectQuery = string() SQL SELECT query.
  • TimeOut = time_out()
  • 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 NrRows will have the value undefined.

🫶 select — choose your rows, choose your destiny 🫶

select(Ref, Position, N) ->
select(Ref, Position, N, TimeOut) -> {selected, ColNames, Rows} |
{error, Reason}

Types:

  • Ref = connection_reference()
  • Position = next | {relative, Pos} | {absolute, Pos} Selection strategy, determines at which row in the result set to start the selection.
  • Pos = integer() Should indicate a row number in the result set. When used together with the option relative it will be used as an offset from the current cursor position, when used together with the option absolute it will be interpreted as a row number.
  • N = integer()
  • TimeOut = time_out()
  • 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.

📚 REFERENCES 📚

💖 that's a wrap — source: Ericsson AB · version: odbc 2.14 · page: odbc(3erl) 🎀

📦 where this page comes from