The criteria for consideration of a primary key are: Uniqueness Irreducibility (no subset of the key uniquely identifies a row in the table) Simplicity (so that relational representation & manipulation can be simpler) Stability (should not be altered frequently) Familiarity (meaningful to the user)
It is commonly agreed that primary keys should be immutable (or as stable as possible since immutability can not be enforced in the DB). While there is nothing that will prevent you from updating a primary key (except integrity constraint), it may not be a good idea: From a performance point of view: You will … Read more
For more international use, one schema to consider is the one used by Drupal Address Field. It’s based on the xNAL standard, and seems to cover most international cases. A bit of digging into that module will reveal some nice pearls for interpreting and validating addresses internationally. It also has a nice set of administrative … Read more
You have to make your own custom authentication-provider. Example code: Service to load Users from Hibernate: import org.springframework.security.core.userdetails.UserDetails; import org.springframework.security.core.userdetails.UserDetailsService; import org.springframework.security.core.userdetails.UsernameNotFoundException; @Service(“userDetailsService”) public class UserDetailsServiceImpl implements UserDetailsService { @Autowired private UserDao dao; @Autowired private Assembler assembler; @Transactional(readOnly = true) public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException, DataAccessException { UserDetails userDetails = null; UserEntity userEntity = … Read more
Table • Name recently learned singular is correct Yes. Beware of the heathens. Plural in the table names are a sure sign of someone who has not read any of the standard materials and has no knowledge of database theory. Some of the wonderful things about Standards are: they are all integrated with each other … Read more
You can always construct a full name from its components, but you can’t always deconstruct a full name into its components. Say you want to write an email starting with “Dear Richie” – you can do that trivially if you have a given_name field, but figuring out what someone’s given name is from their full … Read more
Ok, for starters, you don’t really need to use the Haversine formula here. For large distances where a less accurate formula produces a larger error, your users don’t care if the match is plus or minus a few miles, and for closer distances, the error is very small. There are easier (to calculate) formulas listed … Read more
I want to see which method is more efficient in terms of querying in the database. In a multi-tenant database, querying is only part of the problem. Other parts of the problem are cost, data isolation and protection, maintenance, and disaster recovery. These are significant; you can’t consider only query efficiency in a multi-tenant database. … Read more
There are lots of options: WinPhone7Db Perst SQLite (and here) siaqodb db4o Ninja Database Pro Rapid Repository Sterling Effiproz SQL Compact Edition will be coming in the “Mango” update – due later this year
If your independent variable (RHS variable) is a factor or a character taking only one value then that type of error occurs. Example: iris data in R (model1 <- lm(Sepal.Length ~ Sepal.Width + Species, data=iris)) # Call: # lm(formula = Sepal.Length ~ Sepal.Width + Species, data = iris) # Coefficients: # (Intercept) Sepal.Width Speciesversicolor Speciesvirginica … Read more