Look both ways (From each perspective) when trying to determine the relationship.
Not a thing.If one row points to only one row, you might as well join the tables.
Sometimes you think you have a one-to-one relationship, but you don’t. Look both ways (from each perspective) to avoid this.
Taking your database design through these 3 steps will vastly improve the quality of your data.
There are more than 3 Normal Forms, but usually 3 is the norm. There are more than 6.
Each of the columns and tables should contain one and only one value without it repeating.
Usually every 1NF problem is solved by creating a new table. One of the signs for the need is when columns start having the same name with a number differentiating them. Computer1, Computer2…
Any non-key field should be dependent on the entire primary key i.e. “Can I figure out any of the values in the row from just part of the composite key?”. Only a problem when dealing with composite keys.
No non-key field is dependent on any other non-key field i.e. “Can I figure out any of the values in this row from any of the other values?”.
Sometimes tables intentionally break normalization, and some only seem like they do.
Creating a new table for phones and emails would complicate things needlessly. The same goes for the area codes.
