Comparing two tables in SQLite

SELECT DISTINCT Field1
FROM Table1 
WHERE Field1 Not IN 
    (SELECT DISTINCT Field1 FROM Table2)

SELECT columns1 FROM table1 EXCEPT SELECT columns2 FROM table2;

The SQLite EXCEPT clause returns all rows from the left SELECT statement that are not in the result of the second SELECT statement. The number of columns selected must be the same in both SELECT statements.

This works fine for small to medium size tables. Avoid for tables with millions of lines.

See Compound Select Statements and the documentation of the SQLite SELECT statement.