MySQL Compare Tables and generate delta
1)

SELECT t1.*
FROM current_table t1
LEFT JOIN previous_table t2 ON t1.field1 = t2.field1
                           AND t1.field2 = t2.field2
                     --    another fields in tables structures
                           AND t1.fieldN = t2.fieldN
WHERE t2.fieldX IS NULL /* fieldX - any field defined as NOT NULL */


2)

SELECT t2.*, 
       t1.fieldZ -- new value
FROM current_table t1
INNER JOIN previous_table t2 ON t1.field1 = t2.field1
                            AND t1.field2 = t2.field2
                      --    another static fields in tables structures
                            AND t1.fieldN = t2.fieldN
                      --    altered field
                            AND t1.fieldZ != t2.fieldZ
                      /* if more than one field may be changed, then
                            AND (     t1.fieldZa != t2.fieldZa
                                   OR t1.fieldZb != t2.fieldZb
                               --  OR ...
                                )
                      */