in.dat

原始数据——网络技术

You may WANT A FIELD in field in each record to uniquely identify that1234
record from all other records IN THE FILE. For example, the Employee123456
Number field is unique if you DO NOT ASSIGN the same number to two12345678
different employees, and you never reassign THESE NUMBERS to other12345678
employees. If you wish to FIND OR MODIFY the record belonging to a11111111
specific employee, this unique FIELD SAVES the thouble of determining22222
whether you have the correct record.12345678901234567
If you do not have a unique field, YOU MUST FIND THE first record123456787
the matches your key and determine whether THEN RECORD is the one you33333
want. If it is not the CORRECT ONE, you must search again to find others.4