Cursor Oracle PLSQL Tutorial

Never add a RETURN clause before closing the cursor.
In the exception-handling block, always check to see whether explicit cursors are open, and if so, close them.
Forgotten cursors that are left open can bring a system to a halt.

SQL>
SQL> -- create demo table
SQL> create table Employee(
  2    ID                 VARCHAR2(4 BYTE)         NOT NULL,
  3    First_Name         VARCHAR2(10 BYTE),
  4    Last_Name          VARCHAR2(10 BYTE),
  5    Start_Date         DATE,
  6    End_Date           DATE,
  7    Salary             Number(8,2),
  8    City               VARCHAR2(10 BYTE),
  9    Description        VARCHAR2(15 BYTE)
 10  )
 11  /
Table created.
SQL>
SQL> -- prepare data
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2               values ('01','Jason',    'Martin',  to_date('19960725','YYYYMMDD'), to_date('20060725','YYYYMMDD'), 1234.56, 'Toronto',  'Programmer')
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values('02','Alison',   'Mathews', to_date('19760321','YYYYMMDD'), to_date('19860221','YYYYMMDD'), 6661.78, 'Vancouver','Tester')
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values('03','James',    'Smith',   to_date('19781212','YYYYMMDD'), to_date('19900315','YYYYMMDD'), 6544.78, 'Vancouver','Tester')
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values('04','Celia',    'Rice',    to_date('19821024','YYYYMMDD'), to_date('19990421','YYYYMMDD'), 2344.78, 'Vancouver','Manager')
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values('05','Robert',   'Black',   to_date('19840115','YYYYMMDD'), to_date('19980808','YYYYMMDD'), 2334.78, 'Vancouver','Tester')
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values('06','Linda',    'Green',   to_date('19870730','YYYYMMDD'), to_date('19960104','YYYYMMDD'), 4322.78,'New York',  'Tester')
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values('07','David',    'Larry',   to_date('19901231','YYYYMMDD'), to_date('19980212','YYYYMMDD'), 7897.78,'New York',  'Manager')
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values('08','James',    'Cat',     to_date('19960917','YYYYMMDD'), to_date('20020415','YYYYMMDD'), 1232.78,'Vancouver', 'Tester')
  3  /
1 row created.
SQL>
SQL> -- display data in the table
SQL> select * from Employee
  2  /
ID   FIRST_NAME LAST_NAME  START_DAT END_DATE      SALARY CITY       DESCRIPTION
---- ---------- ---------- --------- --------- ---------- ---------- ---------------
01   Jason      Martin     25-JUL-96 25-JUL-06    1234.56 Toronto    Programmer
02   Alison     Mathews    21-MAR-76 21-FEB-86    6661.78 Vancouver  Tester
03   James      Smith      12-DEC-78 15-MAR-90    6544.78 Vancouver  Tester
04   Celia      Rice       24-OCT-82 21-APR-99    2344.78 Vancouver  Manager
05   Robert     Black      15-JAN-84 08-AUG-98    2334.78 Vancouver  Tester
06   Linda      Green      30-JUL-87 04-JAN-96    4322.78 New York   Tester
07   David      Larry      31-DEC-90 12-FEB-98    7897.78 New York   Manager
08   James      Cat        17-SEP-96 15-APR-02    1232.78 Vancouver  Tester
8 rows selected.
SQL>
SQL> create or replace function f_getList_tx
  2      (i_source_tx VARCHAR2,
  3       i_column_tx VARCHAR2,
  4       i_filter_tx VARCHAR2,
  5       i_separator_tx VARCHAR2)
  6  return VARCHAR2
  7  is
  8      v_string_tx VARCHAR2(4000);
  9      v_temp_tx   VARCHAR2(4000);
 10      v_out_tx    VARCHAR2(4000);
 11      v_weak_ref sys_refcursor;
 12  begin
 13      v_string_tx:='select '||i_column_tx||
 14                   ' from '||i_source_tx||
 15                   ' where '||i_filter_tx;
 16      open v_weak_ref for v_string_tx;
 17      loop
 18          fetch v_weak_ref into v_temp_tx;
 19          exit when v_weak_ref%NOTFOUND;
 20
 21          if v_out_tx is null then
 22              v_out_tx:=v_temp_tx;
 23          else
 24              v_out_tx:=v_out_tx||i_separator_tx||v_temp_tx;
 25          end if;
 26      end loop;
 27
 28      close v_weak_ref;
 29      return v_out_tx;
 30  exception
 31      when others then
 32          if  v_weak_ref%isOpen then
 33                close v_weak_ref;
 34                raise;
 35          end if;
 36  end;
 37  /
Function created.
SQL> select f_getList_tx('employee','first_name','salary > 200',',') from dual;
F_GETLIST_TX('EMPLOYEE','FIRST_NAME','SALARY>200',',')
--------------------------------------------------------
Jason,Alison,James,Celia,Robert,Linda,David,James
SQL>
SQL> -- clean the table
SQL> drop table Employee
  2  /
Table dropped.
SQL>