Overview

When using a command block with a selector like, @e[score_objective=0], any entities that have a null value for their 'objective' score will not be included.

Example

Commands

/summon Creeper
/summon Squid
/scoreboard objectives add magicNum dummy
/scoreboard players set @e[type=Creeper] magicNum 0
/execute @e[score_magicNum=0] ~ ~ ~ say Hi

Output

[Creeper] Hi

Additional Information

When calling the command:
/execute @e[type=Squid,score_magicNum=0] ~ ~ ~ say Hi
No output is given.