How the database is linked (i)

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How the database is linked (i)

(ODBC article)

1. Production:


Database
Early database connectivity is very difficult. Because the format of the various databases is different, developers have to have a deep understanding of the underlying APIs for each database they develop. As a result, a common API that handles a wide variety of databases comes into-―ODBC (Open database Connectivity), an early product of people creating generic APIs. You can use the same code to access different data products in your program, so there are a number of databases (such as access, Ms-sql Server, Oracle, Informix, etc.) that conform to this standard and are called ODBC-compliant databases. The specific role of ODBC is shown in the figure:











In general, ODBC consists of an extended set of DLLs (dynamic link library DLL), which provides a standard database application design interface. ODBC is based on a standardized SQL (Structuredquerylanguage, Structured Query language). So with ODBC and SQL, you can write data access programs that are independent of any database product.

2. Connect the database with ODBC:

There are three types of DSNs available in ODBC, and the difference is simple: a user DSN can only be used for this user. The difference between a System DSN and a file DSN is only that the connection information is stored in a different location: The System DSN is stored in an ODBC storage area, and the file DSN is placed in a text file.

When using them in ASP, the following are written:

A. Linked SQL Server:

Using System DSN:

Connstr= "Dsn=dsnname; Uid=xx; Pwd=xxx;database=dbname "

To use a file DSN:

Connstr= "FILEDSN=XX; Uid=xx; Pwd=xxx;database=dbname "

You can also use a connection string (thereby eliminating the need to create a DSN):

Connstr= "Driver={sql SERVER}; Server=servername; Uid=xx; Pwd=xxx "

B. Link Access:

Using System DSN:

Connstr= "Dsn=dsnname"

(or for: connstr= "dsn=dsnname; Uid=xx; Pwd=xxx ")

To use a file DSN:

Connstr= "Filedsn=xx"

You can also use a connection string (thereby eliminating the need to create a DSN):

Connstr= "Driver={microsoft Access DRIVER};D Bq=d:\abc\abc.mdb"

3, defects:

ODBC contains a large number of low-level calls, so developing an ODBC application is also difficult. Developers have to devote a lot of their energy to the underlying database communications and not focus on the data they are working on.