Sum: You can only use this statement within a LOOP. If you use SUM in an AT - ENDAT block, the system calculates totals for the numeric fields of all lines in the current line group and writes them to the corresponding fields in the work area. If you use the SUM statement outside an AT - ENDAT block (single entry processing), the system calculates totals for the numeric fields of all lines of the internal table in each loop pass and writes them to the corresponding fields of the work area. It therefore only makes sense to use the SUM statement in AT...ENDAT blocks. If the table contains a nested table, you cannot use the SUM statement. Neither can you use it if you are using a field SYMBOL instead of a work area in the LOOP statement.

COLLECT : It allows you to CREATE unique or summarized datasets. The system first tries to find a table entry corresponding to the table key. The key values are taken EITHER from the HEADER line of the internal table itab, or from the explicitly-specified work area wa.

Sum: You can only use this statement within a LOOP. If you use SUM in an AT - ENDAT block, the system calculates totals for the numeric fields of all lines in the current line group and writes them to the corresponding fields in the work area. If you use the SUM statement outside an AT - ENDAT block (single entry processing), the system calculates totals for the numeric fields of all lines of the internal table in each loop pass and writes them to the corresponding fields of the work area. It therefore only makes sense to use the SUM statement in AT...ENDAT blocks. If the table contains a nested table, you cannot use the SUM statement. Neither can you use it if you are using a field symbol instead of a work area in the LOOP statement.

COLLECT : It allows you to create unique or summarized datasets. The system first tries to find a table entry corresponding to the table key. The key values are taken either from the header line of the internal table itab, or from the explicitly-specified work area wa.