Fusion SQL Linking between GL Transactions and PA to obtain the expenditure item id

I have been asked to update a BIP GL report to provide the expenditure item id, should it exist, from projects.

I have done lots of searches and some AI. The responses seem to key around the gl_je_lines.gl_sl_link_id, however if I do a select distinct gl_sl_link_id from gl_je_lines I get a null ()

I can see other data in the table fine, but this key column is blank.

AI gave me this code;

SELECT gl.je_header_id, gl.je_line_num, xdl.source_distribution_id_num_1 AS expenditure_item_id, pei.project_id, p.segment1 AS project_number