Open Database Connectivity

ODBC definiert eine gemeinsame Schnittstelle für den Zugriff auf Datenbanken verschiedener Hersteller.

Installation

UnixODBC verwendet dynamisch ladbare Bibliotheken als Treiber.

apt install unixodbc-dev libsqliteodbc …

Jeder Treiber für ein bestimmtes Datenbank-Managemement-System veranlasst einen Eintrag in die Konfigurationsdatei.

/etc/odbcinst.ini
[sqlite3]
Description=SQLite3 ODBC Driver
Driver=libsqlite3odbc.so
Setup=libsqlite3odbc.so
UsageCount=1

Eine weitere Konfigurationsdatei enthält Einträge mit den Verbindungs- und Zugangsdaten für bestimmte Datenquellen (DSNs).

/etc/odbc.ini
[demo]
Description=Demo Database
Driver=sqlite3
Database=/var/lib/sqlite/demo.db
Timeout=2000

Beispiel

#include <sql.h>
#include <sqlext.h>

int
main (int argc, char * argv)
{
	SQLHENV     env;
	SQLHDBC     dbc;
	SQLHSTMT    stmt;
	SQLSMALLINT len;
	SQLLEN      ind;
	SQLCHAR     buf[BUFSIZ];

	if (SQL_SUCCEEDED (SQLAllocEnv (&env))
	&&  SQL_SUCCEEDED (SQLAllocConnect (env, &dbc))
	&&  SQL_SUCCEEDED (SQLDriverConnect (dbc, NULL,
			(SQLCHAR *) "DSN=demo", SQL_NTS,
			buf, sizeof (buf), &len, SQL_DRIVER_COMPLETE))) {
		SQLAllocStmt (dbc, &stmt);
		SQLExecDirect (stmt, (SQLCHAR *) "SELECT id FROM demo", SQL_NTS);
		while (SQL_SUCCEEDED (SQLFetch (stmt))) {
			SQLGetData (stmt, 1, SQL_C_CHAR,
					buf, sizeof (buf), &ind);
		}
		SQLFreeStmt (stmt, SQL_CLOSE);
	}
	SQLDisconnect  (dbc);
	SQLFreeConnect (dbc);
	SQLFreeEnv     (env);
	return 0;
}

Übersetzn und binden mit:

gcc -g -Wall -lodbc -o odbc odbc.c

API-Referenz

Handles
	SQLHENV env
	SQLHDBC dbc
	SQLHSTMT stm
	SQLHDESC dsc
Allgemein
	SQLAllocHandle	(type, input, * output);
	SQLCancelHandle	(type, input);
	SQLFreeHandle	(type, handle);
	SQLGetDiagField	(type, handle,
		rec, identifier,
		info, max, * length);
	SQLGetDiagRec	(type, handle,
		rec, state, * native,
		message, max, * length);
Environment
	SQLAllocEnv	(SQLHENV * env);
	SQLFreeEnv	(env);
	SQLGetEnvAttr	(env, attr, value, * length);
	SQLSetEnvAttr	(env, attr, value, length);
	SQLDataSources	(env, direction,
		server, max1, * length1,
		desc, max2, * length2);
	SQLError	(env, dbc, stm,
		state, * native,
		message, max, * length);
Connection
	SQLAllocConnect	(env, SQLHDBC * dbc);
	SQLFreeConnect	(dbc);
	SQLConnect	(dbc, server, length1,
		username, length2,
		password, length3);
	SQLDisconnect	(dbc);
	SQLGetFunctions	(dbc, func, * supported);
	SQLGetInfo	(dbc, type, info, max, * length);
	SQLGetConnectAttr	(dbc, attr, value, * length);
	SQLSetConnectAttr	(dbc, attr, value, length);
	SQLGetConnectOption	(dbc, option, value);
	SQLSetConnectOption	(dbc, option, value);
	SQLTransact	(env, dbc, completion);
	SQLEndTran	( type, handle, completion);
Schema
	SQLTables	(stm, catalog, length1,
		schema, length2,
		table, length3,
		type, length4);
	SQLColumns	(stm, catalog, length1,
		schema, length2,
		table, length3,
		column, length4);
	SQLSpecialColumns	(stm, type,
		catalog, length1,
		schema, length2,
		table, length3,
		scope, nullable);
	SQLDescribeCol	(stm, column,
		name, max, * length,
		* type, * size,
		* digits, * nullable);
	SQLColAttribute	(stm, column, field,
		charattr, max, * length,
		* num_attr);
	SQLGetTypeInfo	(stm, type);
	SQLStatistics	(stm, catalog, length1,
		schema, length2,
		table, length3,
		unique, reserved);
Descriptor
	SQLGetDescField	(dsc, rec, field, value, * length);
	SQLSetDescField	(dsc, rec, field, value, max);
	SQLGetDescRec	(dsc, rec, name, max, * length,
		* type,
		* subtype,
		* length,
		* precision,
		* scale,
		* nullable);
	SQLSetDescRec	(dsc, rec,
		type,
		subtype,
		length,
		precision,
		scale,
		data, * length2, * indicator);
	SQLCopyDesc	(dsc, SQLHDESC target);
Statement
	SQLAllocStmt	(dbc, SQLHSTMT * stm);
	SQLFreeStmt	(stm, opt);
	SQLExecDirect	(stm, statement, length);
	SQLGetStmtAttr	(stm, attr, value, * length);
	SQLSetStmtAttr	(stm, attr, value, length);
	SQLGetStmtOption	(stm, option, value);
	SQLSetStmtOption	(stm, option, value);
Bind
	SQLPrepare	(stm, statement, length);
	SQLSetParam	(stm, number, vtype, ptype, precision,
		scale, value, * indicator);
	SQLParamData	(stm, * value);
	SQLBindParam	(stm, number, vtype, ttype, precision,
		scale, value, * indicator);
	SQLBindCol	(stm, column, ttype,
		target, max, * indicator);
	SQLExecute	(stm);
	SQLCancel	(stm);
Fetch
	SQLNumResultCols	(stm, * count);
	SQLRowCount	(stm, * count);
	SQLFetch	(stm);
	SQLFetchScroll	(stm, orientation, offset);
	SQLGetData	(stm, column, ttype,
		target, max, * indicator);
	SQLPutData	(stm, source, indicator);
Cursor
	SQLGetCursorName	(stm, cursor, max, * length);
	SQLSetCursorName	(stm, cursor, length);
	SQLCloseCursor	(stm);

SQL_HANDLE_ENV
SQL_HANDLE_DBC
SQL_HANDLE_STMT
SQL_HANDLE_DESC

SQL_C_CHAR
SQL_C_SHORT
SQL_C_LONG
SQL_C_FLOAT
SQL_C_DOUBLE

SQL_PARAM_TYPE_UNKNOWN
SQL_PARAM_INPUT
SQL_PARAM_OUTPUT
SQL_PARAM_INPUT_OUTPUT

SQL_CLOSE
SQL_DROP
SQL_UNBIND
SQL_RESET_PARAMS

SQL_FETCH_LAST
SQL_FETCH_PRIOR
SQL_FETCH_ABSOLUTE
SQL_FETCH_RELATIVE

SQLTables_TABLE_CATALOG
SQLTables_TABLE_SCHEM
SQLTables_TABLE_NAME
SQLTables_TABLE_TYPE
SQLTables_REMARKS

SQLColumns_TABLE_CAT
SQLColumns_TABLE_SCHEM
SQLColumns_TABLE_NAME
SQLColumns_COLUMN_NAME
SQLColumns_DATA_TYPE
SQLColumns_TYPE_NAME
SQLColumns_COLUMN_SIZE
SQLColumns_BUFFER_LENGTH
SQLColumns_DECIMAL_DIGITS
SQLColumns_NUM_PREC_RADIX
SQLColumns_NULLABLE
SQLColumns_REMARKS
SQLColumns_COLUMN_DEF
SQLColumns_SQL_DATA_TYPE
SQLColumns_SQL_DATETIME_SUB
SQLColumns_CHAR_OCTET_LENGTH
SQLColumns_ORDINAL_POSITION
SQLColumns_IS_NULLABLE

SQL_MAX_DRIVER_CONNECTIONS
…
SQL_OUTER_JOIN_CAPABILITIES

SQL_API_SQLALLOCCONNECT
…
SQL_API_SQLTABLES

SQL_FETCH_FIRST
SQL_FETCH_NEXT

SQL_COMMIT
SQL_ROLLBACK