Code Error with Case Statement

Question

Hi everyone,
I'm new to PL/SQL and APEX and I'm trying to get this code to work. It is supposed to insert an sysdate if the named fields are changed and then update the fields.
This is the code:
BEGIN
SELECT ATS_CLS_NAME, ATS_CEL_NAME, ATS_END_DATE,
CASE
WHEN
ATS_CLS_NAME <> :P6_ATS_CLS_NAME
AND ATS_CLS_NAME <> :P6_ATS_CEL_NAME
AND ATS_END_DATE is Null
THEN
UPDATE ATS_ALLOCATION
SET
ATS_ALLOCATION_ID = :P6_ATS_ALLOCATION_ID,
ATS_START_DATE = :P6_ATS_START_DATE,
ATS_END_DATE = SYSDATE,
ATS_CLS_NAME = :P6_ATS_CLS_NAME,
ATS_CEL_NAME = :P6_ATS_CEL_NAME,
ATS_EMP_ID = :P6_EMP_EMP_ID
ELSE
UPDATE ATS_ALLOCATION
SET
ATS_ATS_ALLOCATION = :P6_ATS_ALLOCATION,
ATS_START_DATE = :P6_ATS_START_DATE,
ATS_END_DATE = :P6_ATS_END_DATE,
ATS_CLS_NAME = :P6_ATS_CLS_NAME,
ATS_CEL_NAME = :P6_ATS_CEL_NAME,
ATS_EMP_ID = :P6_EMP_EMP_ID
FROM ATS_ALLOCATION
END CASE;
END;
And I get this error:
1 error has occurred
ORA-06550: line 12, column 7: PL/SQL: ORA-00936: missing expression ORA-06550: line 5, column 1: PL/SQL: SQL Statement ignored

Answer 1

BEGIN
UPDATE ATS_ALLOCATION
SET
ATS_ATS_ALLOCATION = :P6_ATS_ALLOCATION,
ATS_START_DATE = :P6_ATS_START_DATE,
ATS_END_DATE = CASE
     WHEN ATS_CLS_NAME <> :P6_ATS_CLS_NAME
     AND ATS_CLS_NAME <> :P6_ATS_CEL_NAME
     AND ATS_END_DATE is Null
     THEN SYSDATE
     ELSE :P6_ATS_END_DATE
END,
ATS_CLS_NAME = :P6_ATS_CLS_NAME,
ATS_CEL_NAME = :P6_ATS_CEL_NAME,
ATS_EMP_ID = :P6_EMP_EMP_ID
END;
1 error has occurred
ORA-06550: line 18, column 3: PL/SQL: ORA-00933: SQL command not properly ended ORA-06550: line 4, column 1: PL/SQL: SQL Statement ignored ORA-06550: line 21, column 21: PLS-00103: Encountered the symbol "end-of-file" when expecting one of the following: begin case declare end exception exit for goto if loop mod null pragma raise return select update while with