Is an Overuse of Nullable Columns in a Database a "Code Smell"

MySQL: NULL vs

Use default null. In SQL, null is very different from the empty string (""). The empty string specifically means that the value was set to be empty; null means that the value was not set, or was set to null. Different meanings, you see.

The different meanings and their different usages are why it's important to use each of them as appropriate; the amount of space potentially saved by using default null as opposed to default "" is so small that it approaches negligibility; however, the potential value of using the proper defaults as convention dictates is quite high.

Null values for variables in VBA

Dim x As Variant
x = Null

Only the Variant data type can hold the value Null.

A Variant is a special data type that can contain any kind of data [...] A Variant can also contain the special values Empty, Error, Nothing, and Null.

The "point" of all the other data types is precisely that they cannot contain any ol' kind of data. This has two advantages that I can think of:

• It's more difficult for the programmer to assign data of an unintended type to the variable by mistake, since this will be detected at compile time. This can help prevent bugs and make things clearer for you and the next person who will be maintaining your code.
• Narrow data types save storage space. Putting integers in a Variant (16 bytes) takes up way more memory than putting them in an Int (2 bytes). This becomes significant if you have large arrays.

Of course, Variants do have their place, as other threads on this site discuss.

BAML Decompiler / Viewer

You might like to have another look at the BAML addin for reflector as it's been recently updated by Andrew Smith. Have a look at his at blog post you'll note that he has fixed the issue with path data.

Setting default values for columns in JPA

Actually it is possible in JPA, although a little bit of a hack using the columnDefinition property of the @Column annotation, for example:

@Column(name="Price", columnDefinition="Decimal(10,2) default '100.00'")

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