Try this...
data: lv_stmt type string,
lv_parnr type parnr.
lv_parnr = '1234567890'.
lv_stmt = 'SELECT ...... where personnelnumber = '. (make sure you have space after =)
concatenate lv_stmt lv_parnr '''' into lv_stmt. (after lv_parnr it is ' ' ' ' without spaces).
If it does not work please let me know the lv_stmt data after above concatenate statement.