Sign Up to our social questions and Answers Engine to ask questions, answer people’s questions, and connect with other people.
Login to our social questions & Answers Engine to ask questions answer people’s questions & connect with other people.
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Please briefly explain why you feel this question should be reported.
Please briefly explain why you feel this answer should be reported.
Please briefly explain why you feel this user should be reported.
I know that the order in which a database stores data in a table is random – provided there is no primary key. My question is, fundamentally, what’s going on when the data changes order after a query? If one opened a database, closed it and opened it again to find the data in a different order, what’s going on when that happens?
Its, probably, the question about realization – so it depends on what DBMS you’re using.
The simplest answer – data from this table gone out of DBMS cache and will be read from disk in arbitrary order, if not specified with explicit ORDER BY operator.
The main issue of non-existing primary key – the loss of data consistency. The only reason for table not to have primary key – when the table is a staging (buffer) table.