An example of using MCS to find duplicate Custom Column values in the current library has been attached to the Original Post:
https://www.mobileread.com/forums/sh...d.php?t=261712
The attachment file name is: mcs_sql_search_duplicates_in_single_custom_column. jpg
MCS already has a special function for
cross-library duplicates of Custom Columns, which has not changed. See the "CL Duplicates" checkbox in the middle of the Intra-Book/Inter-Book Query Tab of MCS.
DaltonST