Difference between revisions of "Null"
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* Null parameter/variable - This basically means "pointer to nothing" and is used by some functions to mean you don't have anything to pass it. | * Null parameter/variable - This basically means "pointer to nothing" and is used by some functions to mean you don't have anything to pass it. | ||
* Null character - Null characters have an [[Wikipedia:ASCII|ASCII]] code of 0 and are sometimes used to mark the end of strings or to separate multiple values. | * Null character - Null characters have an [[Wikipedia:ASCII|ASCII]] code of 0 and are sometimes used to mark the end of strings or to separate multiple values. | ||
| − | * Null values in databases - Null is used show the database field has nothing in it. This is different to 0 or an empty string ("") which are both valid values. | + | * Null values in databases - Null is used to show the database field has nothing in it. This is different to 0 or an empty string ("") which are both valid values. |
There are several "Nulls" in VB, all of which are easily confused. | There are several "Nulls" in VB, all of which are easily confused. | ||
Revision as of 09:26, 30 August 2005
Null in the computer world basically means "nothing".
It is normally used in 3 main contexts:
- Null parameter/variable - This basically means "pointer to nothing" and is used by some functions to mean you don't have anything to pass it.
- Null character - Null characters have an ASCII code of 0 and are sometimes used to mark the end of strings or to separate multiple values.
- Null values in databases - Null is used to show the database field has nothing in it. This is different to 0 or an empty string ("") which are both valid values.
There are several "Nulls" in VB, all of which are easily confused.
Uses of Null in VB:
- vbNull - This should only be used when working with the VarType() function. You will have very little cause to use this.
- vbNullChar - This is the Null character mentioned earlier and is the same as Chr$(0)
- vbNullString - A Null string is a pointer to nothing (0) which is subtly different to an empty string (a pointer to a zero length string). In most cases these are interchangable in VB.
- Nothing - The Nothing keyword is used when working with objects and is basically a pointer to nothing. This is the state of all uninitialized object variables and is also used to release an object.
