r_range1-sign   = 'I'.
r_range1-option = 'EQ'.
r_range2-sign   = 'I'.
r_range2-option = 'EQ'.

SELECT field1  FIELD2 from TABLE
into lv_field1,lv_field2
where ...
r_range1-low = lv_field1.
append r_range1.
r_range2-low = lv_field2.
append r_range2.

endselect.

Advantages of Field Symbols

When you read from an internal table, there are no overheads for copying the table line to the work area. When you change an internal table with the MODIFY statement, you must first fill a work area with values, and then assign them to the internal table. If you work with field symbols instead, you do not have this overhead. This can improve performance if you have large or complex internal tables. It also makes it easier to process nested internal tables.

Overheads of READ

Note that internal overheads arise when you access internal tables using field symbols. After a READ statement with a field symbol, the system has to register the assignment. When you delete a table line to which a field symbol is pointing, the system also has to unassign the field symbol to prevent it from pointing to an undefined area.

When you read individual table lines, it is worth using field symbols with the READ statement for tables with a line width of 1000 bytes or more. If you also change the line using the MODIFY statement, using field symbols is worthwhile from a line width of 100 bytes onwards.