... operand IS [NOT] INITIAL ...
The logical expression checks if the operand operand is initial. The expression is true, if the operand contains its type-specific initial value. For operand, you can specify data objects, built-in functions (since Release 6.10) and functional methods. The latter use the return value as operand.
With the addition NOT, the expression is true if the operand contains a different value than its type-specific initial value
The logical expression in the IF statement is true if the internal table in the SELECT statement was filled with rows.
DATA spfli_tab TYPE TABLE OF spfli.
...
CLEAR spfli_tab.
SELECT *
FROM spfli
INTO TABLE spfli_tab
WHERE ...
IF spfli_tab IS NOT INITIAL.
...
ENDIF.