[Help] What are the database connection methods ??

[Help] What are the database connection methods ?? -- Linux general technology-Linux technology and application information. For details, refer to the following section. 1. There are three main database connection methods:
A. ODBC (divided into creating data sources and not creating data sources)
(1) Create a system data source. Use the ODBC function provided by PHP. (Debugging has a problem !!!!!!!)
Establish an odbc driver and connect it with the odbc_connect () function of php.
Reference content is as follows:
For example: $ connstr = DRIVER = {Microsoft Access Driver (*. mdb)}; DBQ = ". $ db;
$ Connid = odbc_connect ($ connstr, "username", "password", SQL _CUR_USE_ODBC );
(2) No need to create a data source (debugging successful !)
$ Connstr = "DRIVER = {Microsoft Access Driver (*. mdb)}; DBQ =". realpath ("db/test. mdb ");
$ Connid = odbc_connect ($ connstr, "", "", SQL _CUR_USE_ODBC );
$ SQL = "select * from userinfo ";
$ Result = odbc_exec ($ connid, $ SQL); // execute an SQL statement

If ($ result) echo "successful ";
Else echo "failed ";
B. ADODB (debugging successful !)
$ Conn = new com ("ADODB. Connection ");
$ Connstr = "DRIVER = {Microsoft Access Driver (*. mdb)}; DBQ =". realpath ("db/test. mdb ");
$ Conn-> Open ($ connstr );
$ Rs = new com ("ADODB. RecordSet ");
$ Rs-> Open ("select * from userinfo", $ conn, 1, 2 );
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C. OLE_DB (similar to the connection string type) (debugging failed !!)
Use oledb to connect and then call the open Method to open
For example, the reference content is as follows:
$ Conn = new com ("ADODB. connection ");
$ Connstr = "Provider = Microsoft. Jet. OLEDB.4.0; Data Source =". $ db;
$ Conn-> Open ($ connstr );
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What should I do if the above failed connections are correct ???
What are the scenarios where ODBC has data sources and data sources ?? There are three main Database Connection Methods: ODBC, OLE_DB, and ADODB. What are their differences? Which one is better ??
In addition, when using ODBC to connect to a database, you can establish a data source connection or do not need to establish a data source connection. What is the difference ??
If there is a difference, where are they used ?? Please explain in detail ????