Adding what you said Jörg,
You can also (if you want to bring only one record) in this way:
DATA v_afield LIKE atable-field.
SELECT SINGLE afield
FROM atable
INTO v_afield
WHERE cfield EQ constantvalue.
Other way:
TYPE: BEGIN OF TY_ITAB,
AFIELD TYPE ATABLE-FIELD " Here you assign an table field
END OF TY_ITAB.
DATA WA_ITAB TYPE TY_ITAB.
SELECT afield
FROM atable
INTO wa_itab
WHERE cfield EQ constantvalue
UP TO 1 ROWS.