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The RDBMS library is a set of miscellaneous types and procedures, allowing to access SQL databases from Bigloo application. The library has two layers: generic RDBMS system interface, implemented with use of Bigloo object system, and a number of back-ends, which provide the implementation for particular database vendors.
The rdbms library is designed like ODBC and Perl DB
system, i.e. it has a set of generic procedures and a number of specific
drivers for different database vendors.
At the moment of writing the library supports MySQL, Oracle, PostgreSQL and SQLite. The support of ODBC and INFORMIX is planned still.
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This section describes the driver object types.
The objects of connection type implement database connections.
The objects of session type used to SQL statements and retrieve
the SQL query results. Every session object is bound to only one
connection.
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This section describes procedures for creating and destroying the database connections, and for transaction management.
This procedure creates and opens new database connection. The
vendor-tag is the name of the database system.
The rdbms-drivers thunk returns the list of possible vendor-tag values.
The rest of parameters specify a vendor-specific connection information.
Usually this includes:
dbname
the logical name of database
username
the name of the database user
password
the password of the database user
hostname
the name of the host on which the database server runs
Examples:
(rdbms-connect "mysql" dbname: "test" hostname: "duron") -| #|MYSQL-CONNECTION [IMPL: #<foreign:MYSQL:80947f8>]| (rdbms-connect "oracle" username: "scott" password: "tiger") -| #|oracle-connection [env::oci-env: #<foreign:oci-env:84a2e30>] [impl::oci-svc-ctx: #<foreign:oci-svc-ctx:84a8508>] [err::oci-error: #<foreign:oci-error:84a8574>]| |
Return the list of supported database types, for example:
(print(rdbms-drivers))
-| ("mysql" "pgsql" "oracle" "sqlite")
|
This destroys the connection, and releases all connection's
resources, including all bound session objects.
Return a (vendor-specific) description of the last error occured with
rdbms-object.
Check whether the implementation supports transactions. If yes, begin a transaction and return #t. Otherwise return #f.
The optional argument timeout sets transaction timeout value.
Close the transaction for connection. Some implementations do not
require the begin-transaction call before calling this method,
but you should not call the commit-transaction if the
implementation does not support transactions.
This ends the transaction, revert all changes made since transaction's
beginning. Some implementations do not require the
begin-transaction call before calling this method, but you should
not call the rollback-transaction if the implementation does not
support transactions.
This creates new session for the given connection.
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Cancel the query answering process, if any. Make a session ready
for execution.
Destroy a session object, and release all the
session's resources.
Execute a previously prepared statement. Return #t if the answer set is implied by the statement (i.e. the statement is SQL SELECT command). Otherwise return #f.
Prepares an SQL query for execution. The position of optional parameters
is marked up with parameter number preceded by colon sign. See example
in the bind! section if this manual.
(prepare sess "insert into person values(:1, :2, :3)") (bind! sess '(100 "Tsichevski" "Vladimir")) |
Positionally bind parameters of prepared session.
Example: prepare and bind an SQL INSERT statement. The positions of
bound parameters are marked with :1, :2, and :3.
(prepare sess "insert into person values(:1, :2, :3)") (bind! sess '(100 "Tsichevski" "Vladimir")) |
This answers #t if the answer set is implied by previously prepared statement. Note: some implementation require you have to execute the session before calling this method.
Fetch next record from the query answer set, and return it as a scheme
list object. If the end of the answer stream is reached, return
an empty list.
Example: prepare and execute an SQL statement. Fetch and print all result records.
(prepare sess "select * from person")
(let loop()
(let((value(fetch! self)))
(when(pair? value)
(print value)
(loop))))
|
Describe the result of SQL query. Return a scheme list of column descriptions. The format of column descriptions depends on database imlementation. Typical column descriptors provides the following information:
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In the following example, the connection with MySQL database
named dept is established. Next, the table named person
with columns named id, last_name and first_name is
created and a few records inserted into the table. The contents of the table
is retrieved back then and displayed. After that, the table is
destroyed.
Here is the example :
(define conn
(rdbms-connect "mysql" dbname: "test" hostname: "duron"))
(define sess (acquire conn))
(prepare sess
"create table person (
id INTEGER PRIMARY KEY,
last_name CHAR(20),
first_name CHAR(20))")
(execute sess)
(prepare sess "insert into person values(:1,:2,:3)")
(bind! sess '(100 "Tsichevski" "Vladimir"))
(execute sess)
(bind! sess '(101 "Taranoff" "Alexander"))
(execute sess)
(bind! sess '(102 "Ananin" "Vladimir"))
(execute sess)
(prepare sess "select * from person")
(execute sess)
(let loop ((answer-record(fetch! sess)))
(when(pair? answer-record)
(write answer-record)
(newline)
(loop (fetch! sess))))
(prepare sess "drop table person")
(execute sess)
(dismiss! conn)
|
The output of the program looks like this :
(100 "Tsichevski" "Vladimir") (101 "Taranoff" "Alexander") (102 "Ananin" "Vladimir") |
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