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ColumnKeyExistsQ
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ColumnKeyExistsQ

New in 14.2[Experimental]

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ColumnKeyExistsQ[data,key]

returns True if the specified key exists in the tabular data, and False otherwise.

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represents an operator form of ColumnKeyExistsQ that can be applied to an expression.

Details

Examples

open allclose all

Basic Examples  (1)Summary of the most common use cases

Check whether a column key exists in a Tabular object:

In[1]:=1
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https://wolfram.com/xid/0bnhtm2fn3car-rc2umd
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0bnhtm2fn3car-u4dyi9
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0bnhtm2fn3car-jvpwu1
Out[3]=3

Scope  (7)Survey of the scope of standard use cases

Data Forms  (5)

Check the presence of a column key in a Tabular object:

In[1]:=1
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https://wolfram.com/xid/0bnhtm2fn3car-m4loj6
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0bnhtm2fn3car-hig9fm
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0bnhtm2fn3car-q7v6c9
Out[3]=3

For a Tabular object without column keys, ColumnKeyExistsQ always returns False:

In[1]:=1
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https://wolfram.com/xid/0bnhtm2fn3car-gt97ve
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0bnhtm2fn3car-x3hd8h
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0bnhtm2fn3car-wjc406
Out[3]=3
In[4]:=4
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https://wolfram.com/xid/0bnhtm2fn3car-1mz4jh
Out[4]=4

Check the presence of a key in any of the associations of a list of them:

In[1]:=1
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https://wolfram.com/xid/0bnhtm2fn3car-in5atx
In[2]:=2
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https://wolfram.com/xid/0bnhtm2fn3car-7115qs
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0bnhtm2fn3car-sq64rs
Out[3]=3
In[4]:=4
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https://wolfram.com/xid/0bnhtm2fn3car-6cxlvn
Out[4]=4
In[5]:=5
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https://wolfram.com/xid/0bnhtm2fn3car-2z5sxe
Out[5]=5

ColumnKeyExistsQ effectively assumes Missing[…] values, as Tabular would do:

In[6]:=6
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https://wolfram.com/xid/0bnhtm2fn3car-dfjo26
Out[6]=6

Check the presence of a column key in a Dataset object:

In[1]:=1
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https://wolfram.com/xid/0bnhtm2fn3car-6y70t2
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0bnhtm2fn3car-l4kta7
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0bnhtm2fn3car-dk7wi
Out[3]=3

Use ColumnKeyExistsQ as an operator form:

In[1]:=1
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https://wolfram.com/xid/0bnhtm2fn3car-w5kqk7
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0bnhtm2fn3car-fnn0md
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0bnhtm2fn3car-2r70bv
Out[3]=3

Key Forms  (2)

Check whether a given column key is present in a Tabular object:

In[1]:=1
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https://wolfram.com/xid/0bnhtm2fn3car-sx5lc7
Out[1]=1
In[2]:=2
✖
https://wolfram.com/xid/0bnhtm2fn3car-4oetfv
Out[2]=2

The key in ColumnKeyExistsQ[tab,key] can be wrapped in Key or ExtendedKey:

In[3]:=3
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https://wolfram.com/xid/0bnhtm2fn3car-8yht23
Out[3]=3
In[4]:=4
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https://wolfram.com/xid/0bnhtm2fn3car-tiovt
Out[4]=4

Take a Tabular object with extended column keys:

In[1]:=1
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https://wolfram.com/xid/0bnhtm2fn3car-wtzc2i
Out[1]=1

Check whether a given extended key is present:

In[2]:=2
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https://wolfram.com/xid/0bnhtm2fn3car-rphx2v
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0bnhtm2fn3car-7m63tj
Out[3]=3

Extended keys can be addressed by their last argument if they are unique:

In[4]:=4
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https://wolfram.com/xid/0bnhtm2fn3car-txdn4a
Out[4]=4
In[5]:=5
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https://wolfram.com/xid/0bnhtm2fn3car-v7ve2k
Out[5]=5

Properties & Relations  (2)Properties of the function, and connections to other functions

ColumnKeyExistsQ[tab,key] is equivalent to MemberQ[ColumnKeys[tab],key]:

In[1]:=1
✖
https://wolfram.com/xid/0bnhtm2fn3car-ekrh7j
Out[1]=1
In[2]:=2
✖
https://wolfram.com/xid/0bnhtm2fn3car-kokkz6
Out[2]=2
In[3]:=3
✖
https://wolfram.com/xid/0bnhtm2fn3car-5r0czr
Out[3]=3
In[4]:=4
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https://wolfram.com/xid/0bnhtm2fn3car-6xwttg
Out[4]=4

For a list assocs of associations, ColumnKeyExistsQ[assocs,key] is equivalent to using KeyExistsQ in the associations:

In[1]:=1
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https://wolfram.com/xid/0bnhtm2fn3car-n85osa
Out[1]=1
In[2]:=2
✖
https://wolfram.com/xid/0bnhtm2fn3car-zfealj
Out[2]=2
In[3]:=3
✖
https://wolfram.com/xid/0bnhtm2fn3car-1gorg0
Out[3]=3

ColumnKeyExistsQ returns True if the key exists in any of the associations:

In[4]:=4
✖
https://wolfram.com/xid/0bnhtm2fn3car-kdq94t
Out[4]=4
In[5]:=5
✖
https://wolfram.com/xid/0bnhtm2fn3car-jwx5x
Out[5]=5
Wolfram Research (2025), ColumnKeyExistsQ, Wolfram Language function, https://reference.wolfram.com/language/ref/ColumnKeyExistsQ.html.
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Wolfram Research (2025), ColumnKeyExistsQ, Wolfram Language function, https://reference.wolfram.com/language/ref/ColumnKeyExistsQ.html.

Text

Wolfram Research (2025), ColumnKeyExistsQ, Wolfram Language function, https://reference.wolfram.com/language/ref/ColumnKeyExistsQ.html.

✖
Wolfram Research (2025), ColumnKeyExistsQ, Wolfram Language function, https://reference.wolfram.com/language/ref/ColumnKeyExistsQ.html.

CMS

Wolfram Language. 2025. "ColumnKeyExistsQ." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/ColumnKeyExistsQ.html.

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Wolfram Language. 2025. "ColumnKeyExistsQ." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/ColumnKeyExistsQ.html.

APA

Wolfram Language. (2025). ColumnKeyExistsQ. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/ColumnKeyExistsQ.html

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Wolfram Language. (2025). ColumnKeyExistsQ. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/ColumnKeyExistsQ.html

BibTeX

@misc{reference.wolfram_2025_columnkeyexistsq, author="Wolfram Research", title="{ColumnKeyExistsQ}", year="2025", howpublished="\url{https://reference.wolfram.com/language/ref/ColumnKeyExistsQ.html}", note=[Accessed: 20-June-2025 ]}

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@misc{reference.wolfram_2025_columnkeyexistsq, author="Wolfram Research", title="{ColumnKeyExistsQ}", year="2025", howpublished="\url{https://reference.wolfram.com/language/ref/ColumnKeyExistsQ.html}", note=[Accessed: 20-June-2025 ]}

BibLaTeX

@online{reference.wolfram_2025_columnkeyexistsq, organization={Wolfram Research}, title={ColumnKeyExistsQ}, year={2025}, url={https://reference.wolfram.com/language/ref/ColumnKeyExistsQ.html}, note=[Accessed: 20-June-2025 ]}

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@online{reference.wolfram_2025_columnkeyexistsq, organization={Wolfram Research}, title={ColumnKeyExistsQ}, year={2025}, url={https://reference.wolfram.com/language/ref/ColumnKeyExistsQ.html}, note=[Accessed: 20-June-2025 ]}