More About Bind Variables
uYou cannot pass NULL as a literal – only as a variable
u
uprocedure p_clear_Column
u(i_table_tx,i_clearColumn_tx,i_pkColumn_tx,i_pkValue_nr)is
u  v_sql_tx  varchar2(32000);
v_null_tx varchar2(256):=NULL;
uBegin
u  v_sql_tx:=' update '||i_table_tx||
u        ' set '||i_clearColumn_tx||'=:v01'||
u        ' where  '||i_pkColumn_tx||'=:v02';
u 
u EXECUTE IMMEDIATE v_sql_tx
u  USING v_null_tx, i_pkValue_nr; -- valid
u 
u -- EXECUTE IMMEDIATE v_sql_tx INTO v_out_tx
u  -- USING NULL, i_pkValue_nr;   -- invalid
uend;