ok im trying to figure out a way to compare a table to another to find rows that no longer have a parent. similar to orphan thread but my only problem is that the column names are different but hold the same data. so the USE() function isnt possible and i do not think ON() will work because it will only find the rows that do coinside with table 1 from table 2. basically i want find journals that no longer have journalists and remove them.
SELECT * from table1
LEFT JOIN table2 ON (table1.column1 = table2.column2)
WHERE table2.column2 = NULL
Should find any entries in table1 that don't have a matching entry in table2 (column1 & column2 are the same data you referred to with different names in each table).