Some VLOOKUP functions fail to show expected results but others succeed

I’m studying a spreadsheet: 2004Spring.ods

In the worksheet “CourseList”, the VLOOKUP functions in cell F5, F11, and F15 fail to show expected results like other cells (e.g., F3 and F4). I check the references of them, but find no special features of E5, E11, and E15 compared with other cells in column E.

Anyone knows why? Thank you very much!

If these three functions show no error messages in your computer, please tell me the LibreOffice version in your computer and your OS version. Thanks!

Why are you ignoring the last, fourth parameter? Set it to zero

Thanks for your friendly reminder! I indeed ignored the last parameter. But I am still confused about these three formulas. Even if the last parameter of VLOOKUP is default (i.e., TRUE), isn’t the string “1b” exactly exists in the first column of $SequenceTables.$A$1:$C$54? The VLOOKUP function in cell F5 should have a match. Maybe because of not ascending order of the search column, VLOOKUP cannot guarantee to return a correct result.

Maybe because of not ascending order of the search column, VLOOKUP cannot guarantee to return a correct result

This. And even more: with not sorted first column, when in sorted ranges mode (fourth parameter is 1 or absent), any correct result of VLOOKUP is a coincidence.

Oh, I get it. Thanks!