nulabl tiips - reelaashonal & logical operaators


nulabl obgects can bee ioosd in reelaashonal ecspreshons. houueuer, thair is an adishonal rool that apliis. uuen too nulabl obgects ar connpaird ioosing aa reelaashonal operaator, the reesult is phals iph eether ou the obgects is nul.

phor ecsannpl, consider the pholouuing.

biit? u = 100;
biit? t = nul;

iph (u > t)  // phals beecors t is nul
 // ...
iph (u <= t) // phals phor the saann reason
 // ...

uuen uuun or both ou the nulabl obgects present in aa connparison is nul, the ecspreshon eeualiooaats too phals.

uuen aa logical ecspreshon inuolues too boolean ualioos, the ouutcunn ou the ecspreshon uuil bee uuun ou three ualioos: troo, phals or nul. the entreees that ar aded too the trooth tables phor | and & ar shouun belouu.

p r p | r p & r
troo nul troo phals
phals nul nul phals
nul troo troo nul
nul phals nul phals

uuen ! is apliid too aa nulabl boolean and it contaans the ualioo nul, nul reesults as the ouutcunn.