Updating mysql tables from external file

Although external tables cannot contain a column object, you can use constructor functions to build a column object from attributes in the external table.For example, assume a table in the database is defined as follows: CREATE TABLE roster_data ( student_no CHAR(5), name CHAR(20), grade CHAR(2)) ORGANIZATION EXTERNAL (TYPE ORACLE_LOADER DEFAULT DIRECTORY ext_tab_dir ACCESS PARAMETERS (FIELDS TERMINATED BY ',') LOCATION ('info.dat')); Any conversion errors that occur between the datafile and the external table cause the row with the error to be ignored.

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For example, the following statement creates a directory object named privileges on the directory to other users.statement generates a flow of data from the external data source to the Oracle SQL engine, where data is processed.As data from the external source is parsed by the access driver and provided to the external table interface, it is converted from its external representation to its Oracle internal datatype. The data stream that is unloaded is in a proprietary format and contains all the column data for every row being unloaded.In the context of external tables, loading data refers to the act of reading data from an external table and loading it into a table in the database.Unloading data refers to the act of reading data from a table in the database and inserting it into an external table.

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