"Turn" OLE DB and ODBC and the most visual interpretation of ADO

Prehistoric
At that time each database vendor (in fact, not a few)
have their own database operations API,
Use only one fixed database per application
Want to change the database? No way! You have to write it all back.
Later
X/open and ISO (like IBM) say
How do programmers live in such a mess?
Thereupon the CLI (Call-level Interface) was proposed
The CLI (driver) for each database is basically the same,
The programmer has a better point, but to change the database,
The program you wrote needs to be recompiled (and maybe installed)
and later
So ODBC comes in, it dynamically loads the CLI of each database
To convert a function call into a CLI call for each database
The database application has finally had a relationship with the database vendor.
and later
Ms puts forward the OLE,MS and has its own database.
(Access/sql Server)
MS is the boss, of course, this issue should have their own views
If it's just providing ODBC, that's a lot of embarrassment.
So the OLE DB is proposed, which is called via COM interface
OLE DB also requires a CLI for each database
(but with a term, called provider)
MS has written a provider for access and SQL Server, respectively.
However, in order to take care of ODBC, an ODBC provider is also provided.
This allows ODBC-only databases to be accessed through OLE DB
But it's a little less efficient (because it's going through two levels)
So now some databases will provide their own provider.
and later
Ms says OLE DB interfaces are too complicated.
The programmer also tunes query
There's no need to be so complicated.
The Ado,ado is then presented by encapsulating the above OLE DB
Simplifies the use of methods, the programmer in the operation of the database is finally liberated
The new century has finally arrived.
Ms also invented. NET, in order to adapt to the new trend of the new century
Also proposed by the ADO