MySQL: LOAD DATA INFILE
for csv's; for .sql files generated with MySQL, use the shell.
For SQLite: see this SO question.
SQL Server: apparently there's the BULK INSERT
command.
You are not going to find a database-independent syntax for an SQL command because there isn't one.
There may be a wrapper library around databases but I'm not aware of it. (Or you could try to use ODBC, but that's connection oriented and wouldn't allow direct access to a file)
Perhaps there is an interactive GUI-related software tool out there to do this.
Note also that loading data directly from a file on a database server into a database almost certainly requires security privileges to do so (otherwise it is a security risk).