Explain the following commands:

Db_connect
i. to connect to a database
db_connect(, );
b. db_execute_query
i. to execute a query
db_execute_query ( session_name, SQL, record_number );
record_number is the out value.
c. db_get_field_value
i. returns the value of a single field in the specified row_index and column in the session_name database session.
db_get_field_value ( session_name, row_index, column );
d. db_get_headers
i. returns the number of column headers in a query and the content of the column headers, concatenated and delimited by tabs.
db_get_headers ( session_name, header_count, header_content );
e. db_get_row
i. returns the content of the row, concatenated and delimited by tabs.
db_get_row ( session_name, row_index, row_content );
f. db_write_records
i. writes the record set into a text file delimited by tabs.
db_write_records ( session_name, output_file [ , headers [ , record_limit ] ] );
g. db_get_last_error
i. returns the last error message of the last ODBC or Data Junction operation in the session_name database session.
db_get_last_error ( session_name, error );
h. db_disconnect
i. disconnects from the database and ends the database session.
db_disconnect ( session_name );
i. db_dj_convert
i. runs the djs_file Data Junction export file. When you run this file, the Data Junction Engine converts data from one spoke (source) to another (target). The optional parameters enable you to override the settings in the Data Junction export file.
db_dj_convert ( djs_file [ , output_file [ , headers [ , record_limit ] ] ] );