Create a Tabular object with columns using ExtendedKey:

Extract the column keys:

Extract the columns corresponding to "obs A":

Take a Tabular object with ExtendedKey column keys:

Extract one column as a TabularColumn object:

Extract the same column as another Tabular object:

ExtendedKey[…,key] can be shortened to key if this uniquely identifies the column:

Take a Tabular object with ExtendedKey column keys:

Extract all columns sharing the specified keys:

Using patterns in ExtendedKey is interpreted as producing a list of keys, even if only one:

None of the column keys matches this structure:

Take a Tabular object of Palmer penguin data:

ExtendedKey is created by PivotTable when pivoting on more than one column:

Use ExtendedKey in column transformation:

Take a Tabular object of Palmer penguin data:

ExtendedKey is created by PivotTable when pivoting on more than one column:

Find all column keys for "Adelie" penguins:

Create a "Total" column for all "Adelie" penguins from three islands:

ExtendedKey is stripped in associations when containing only one key:

The symbol remains when containing several keys:

Key lookup in associations requires exact matching:

Using ExtendedKey succeeds in all four cases:

ExtendedKey has Flat attribute:

Nested ExtendedKey wrappers will therefore be automatically flattened:

Key always takes one argument:

ExtendedKey can take more than one argument:

Both keys can then be used to address their values: