SELECT CASE net_weight 
       WHEN net_weight < 1.00 THEN 1
       ELSE net_weight
       END 
FROM SO_PRICE_ADJUSTMENTS;

SQL> create table tbl
  2  (net_weight number(5,2));

Table created.

SQL> insert into tbl values(0.5);

1 row created.

SQL> insert into tbl values(1.5);

1 row created.

SQL> SELECT CASE net_weight 
  2         WHEN net_weight < 1.00 THEN 1
  3         ELSE net_weight
  4         END 
  5  FROM tbl;
       WHEN net_weight < 1.00 THEN 1
                       *
ERROR at line 2:
ORA-00905: missing keyword

SQL> ed
Wrote file afiedt.buf

  1  SELECT CASE
  2         WHEN net_weight < 1.00 THEN 1
  3         ELSE net_weight
  4         END
  5* FROM tbl
SQL> /

CASEWHENNET_WEIGHT<1.00THEN1ELSENET_WEIGHTEND
---------------------------------------------
                                            1
                                          1.5

SELECT CASE  
           WHEN net_weight  > 0.00 and net_weight < 1.00 THEN 1
           ELSE net_weight
           END ,net_weight
    FROM tbl;

WHEN net_weight  > 0 and net_weight < 1 THEN 1

WHEN net_weight  >= 0 and net_weight < 1 THEN 1