Understanding the difference between get and select

In short, get extracts values from its input, while select keeps the structure of its input (a record stays a record, a table stays a table) and only removes the parts you did not ask for.

get extracts the value and returns a single value or list if multiple keys have been specified.

{a: 1, b: 2, c: 3} | get b
# => 2
{a: 1, b: 2, c: 3} | get b c
# => ╭───┬───╮
# => │ 0 │ 2 │
# => │ 1 │ 3 │
# => ╰───┴───╯

select maintains the nushell values and returns the records selected by column name or key.

{a: 1, b: 2, c: 3} | select b
# => ╭───┬───╮
# => │ b │ 2 │
# => ╰───┴───╯
{a: 1, b: 2, c: 3} | select b c
# => ╭───┬───╮
# => │ b │ 2 │
# => │ c │ 3 │
# => ╰───┴───╯

With tables

The examples below use this table:

let t = [[name lang]; [nushell rust] [reedline rust] [vscode-ext typescript]]

For a column, get returns a list of the column's values, while select returns a table with only that column:

$t | get name
# => ╭───┬────────────╮
# => │ 0 │ nushell    │
# => │ 1 │ reedline   │
# => │ 2 │ vscode-ext │
# => ╰───┴────────────╯
$t | select name
# => ╭───┬────────────╮
# => │ # │    name    │
# => ├───┼────────────┤
# => │ 0 │ nushell    │
# => │ 1 │ reedline   │
# => │ 2 │ vscode-ext │
# => ╰───┴────────────╯

For a row index, get returns the row as a record, while select returns a table with only that row:

$t | get 1
# => ╭──────┬──────────╮
# => │ name │ reedline │
# => │ lang │ rust     │
# => ╰──────┴──────────╯
$t | select 1
# => ╭───┬──────────┬──────╮
# => │ # │   name   │ lang │
# => ├───┼──────────┼──────┤
# => │ 0 │ reedline │ rust │
# => ╰───┴──────────┴──────╯

Nested data

Both commands take cell paths. get follows the path and returns the value at the end of it. select keeps a column for the path, named after the whole path:

{a: {b: 1}} | get a.b
# => 1
{a: {b: 1}} | select a.b
# => ╭─────┬───╮
# => │ a.b │ 1 │
# => ╰─────┴───╯

Missing data

Both commands raise an error when a column does not exist. Add ? to a cell-path member, or pass --optional (-o) to make every member optional. get then returns null, and select returns an empty cell:

{a: 1} | get -o z | describe
# => nothing
{a: 1} | select -o z
# => ╭───┬──╮
# => │ z │  │
# => ╰───┴──╯

Both commands also accept --ignore-case to match column names case-insensitively.

See also: Filters to select subsets of data, and Using get and select in the Book.