Oracle 18c

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ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';
CREATE TABLE T_ATTENDANCE_USER_MASTER (
    "LOGINID" VARCHAR2(200 BYTE) NOT NULL ENABLE
)
CREATE TABLE /*"PROMETHEAN".*/"T_ATTENDANCE_ATTENDANCE" (
  "ATTENDANCEID" NUMBER GENERATED ALWAYS AS IDENTITY MINVALUE 1 MAXVALUE 9999999999999999999999999999 INCREMENT BY 1 START WITH 1 CACHE 20 NOORDER NOCYCLE NOKEEP NOSCALE NOT NULL ENABLE,
  "LOGINID" VARCHAR2(200 BYTE) NOT NULL ENABLE,
  "ATTENDANCEDATE" TIMESTAMP (3),
  "SHIFTNAME" VARCHAR2(50 BYTE),
  "SHIFTSTARTTIME" TIMESTAMP (3),
  "SHIFTENDTIME" TIMESTAMP (3),
  "SIGNIN" TIMESTAMP (3),
  "SIGNOUT" TIMESTAMP (3),
  "OLDATTENDANCEID" NUMBER(10,0),
  "ACTIVE" NUMBER(10,0),
  "REMARK" VARCHAR2(255 BYTE),
  "ATTENDANCESTATUS" VARCHAR2(20 BYTE),
  "L1APPROVEDDBY" VARCHAR2(20 BYTE),
  "L1APPROVEDON" TIMESTAMP (3),
  "L2APPROVEDBY" VARCHAR2(20 BYTE),
  "L2APPROVALON" TIMESTAMP (3),
  "CREATEDBY" VARCHAR2(20 BYTE),
  "CREATEDON" TIMESTAMP (3),
  "MODIFIEDBY" VARCHAR2(20 BYTE),
  "MODIFIEDON" TIMESTAMP (3),
  "IPADDRESS" VARCHAR2(100 BYTE),
  "LOGONUSERNAME" VARCHAR2(100 BYTE),
  "COMPOFFDATE" DATE,
  "WORKLOCATIONTYPE" VARCHAR2(10 BYTE),
  "WORKLOCATION" VARCHAR2(50 BYTE),
  PRIMARY KEY ("ATTENDANCEID")
)
CREATE PACKAGE package_name AS
  TYPE t_cursor IS REF CURSOR;

  PROCEDURE getCalendar (
    V_Year VARCHAR2,
    V_Month VARCHAR2,
    V_LoginId varchar2,
    curAttendanceDate OUT T_CURSOR
  );
END;
/
CREATE PACKAGE BODY package_name AS

PROCEDURE getCalendar (
  V_Year VARCHAR2,
  V_Month VARCHAR2,
  V_LoginId varchar2,
  curAttendanceDate OUT T_CURSOR
)

AS
  V_Date  DATE := TO_DATE (V_Year || '-' || V_Month || '-01', 'yyyy-mm-dd');
BEGIN
  MERGE INTO T_ATTENDANCE_ATTENDANCE dst
  USING (
    WITH DaysInMonth (dates) AS (
      SELECT V_Date FROM   DUAL 
    UNION ALL
      SELECT dates + INTERVAL '1' DAY
      FROM   DaysInMonth
      WHERE  dates + INTERVAL '1' DAY < ADD_MONTHS(TRUNC(V_Date, 'MONTH'), 2)
    )
    SELECT u.LoginID,
           d.dates,
           (TRUNC(d.dates, 'IW') - a.start_date) / 7 AS week
    FROM   daysinmonth d
           CROSS JOIN T_ATTENDANCE_USER_MASTER U
           CROSS JOIN LATERAL (
             SELECT TRUNC(COALESCE(MIN(attendancedate), v_date), 'IW') AS start_date
             FROM   T_ATTENDANCE_ATTENDANCE a
             WHERE  u.loginid = a.loginid
           ) a
    WHERE  loginid = V_LoginId
  ) src
  ON (dst.loginid = src.loginid AND dst.attendancedate = src.dates)
  WHEN NOT MATCHED THEN
    INSERT (
      LoginId,
      AttendanceDate,
      ShiftName,
      ShiftStartTime,
      ShiftEndTime,
      Active,
      AttendanceStatus
    ) VALUES (
      src.loginid,
      src.dates,
      CASE
      WHEN (   TRUNC(src.dates) - TRUNC(src.dates, 'IW') = 5
           AND MOD(src.week, 4) IN (1, 3)
           )
      OR   TRUNC(src.dates) - TRUNC(src.dates, 'IW') = 6
      THEN 'WEEKLYOFF'
      ELSE 'GENERAL1'
      END,
      NULL,
      NULL,
      1,
      'Approved'
    );
end getCalendar;

END;
/
SELECT * FROM USER_ERRORS;