# What does a question mark mean next to type in a DataFrame?

**URL:** <https://discourse.julialang.org/t/what-does-a-question-mark-mean-next-to-type-in-a-dataframe/57774>\
**Category:** New to Julia\
**Created:** [March 23, 2021, 8:52am UTC](https://discourse.julialang.org/t/what-does-a-question-mark-mean-next-to-type-in-a-dataframe/57774 "2021-03-23T08:52:35Z")\
**Posts on this page:** 1\
**Showing post:** 3

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**Author:** ![magister-ludi](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/magister-ludi/32/4003_2.png) [@magister-ludi](https://discourse.julialang.org/u/magister-ludi)\
**Post date:** [March 23, 2021, 11:54am UTC](https://discourse.julialang.org/t/what-does-a-question-mark-mean-next-to-type-in-a-dataframe/57774/3 "2021-03-23T11:54:30Z")

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You might like to look at the thread [Difference between `Union{Missing, Float64}` and `Float64?`](https://discourse.julialang.org/t/difference-between-union-missing-float64-and-float64/57542/7)

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