df.single{ age ==45}
df.first{ weight !=null}
df.minBy{ age }
df.maxBy{ name.firstName.length }
df.maxByOrNull{ weight }
val age by column<Int>()val weight by column<Int?>()val name bycolumnGroup()val firstName by name.column<String>()
df.single{age()==45}
df.first{weight()!=null}
df.minBy(age)
df.maxBy{firstName().length }
df.maxByOrNull{weight()}