Google Spreadsheet, copy column in sheet to column in another sheet

If you want to share columns across separate files, you can use:

=importrange("17s-yYzX8GYvyA2PorY2PLaZ5OpFi14wU0ugAyTIrL24","Sheet1!G:J")

where the first string is the key of the sheet file that you want to import from. You can copy that directly from the URL e.g. https://docs.google.com/spreadsheets/d/17s-yYzX8GYvyA2PorY2PLaZ5OpFi14wU0ugAyTIrL24/edit#gid=0. The second string is the name of the sheet in the source file and in the example G:J means import columns G through J.

={'Sheet2'!X:X}

Needs single-quotes around the sheet name.

Use:

=ArrayFormula('Sheet2'!D:D)