Oracle PL/SQL Tutorial/Conversion Functions/DECODE

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Decode as If statement

   <source lang="sql">

SQL> SQL> SQL> create table employees(

 2    empno      NUMBER(4)
 3  , ename      VARCHAR2(8)
 4  , init       VARCHAR2(5)
 5  , job        VARCHAR2(8)
 6  , mgr        NUMBER(4)
 7  , bdate      DATE
 8  , msal       NUMBER(6,2)
 9  , comm       NUMBER(6,2)
10  , deptno     NUMBER(2) ) ;

Table created. SQL> SQL> SQL> insert into employees values(1,"Jason", "N", "TRAINER", 2, date "1965-12-18", 800 , NULL, 10); 1 row created. SQL> insert into employees values(2,"Jerry", "J", "SALESREP",3, date "1966-11-19", 1600, 300, 10); 1 row created. SQL> insert into employees values(3,"Jord", "T" , "SALESREP",4, date "1967-10-21", 1700, 500, 20); 1 row created. SQL> insert into employees values(4,"Mary", "J", "MANAGER", 5, date "1968-09-22", 1800, NULL, 20); 1 row created. SQL> insert into employees values(5,"Joe", "P", "SALESREP",6, date "1969-08-23", 1900, 1400, 30); 1 row created. SQL> insert into employees values(6,"Black", "R", "MANAGER", 7, date "1970-07-24", 2000, NULL, 30); 1 row created. SQL> insert into employees values(7,"Red", "A", "MANAGER", 8, date "1971-06-25", 2100, NULL, 40); 1 row created. SQL> insert into employees values(8,"White", "S", "TRAINER", 9, date "1972-05-26", 2200, NULL, 40); 1 row created. SQL> insert into employees values(9,"Yellow", "C", "DIRECTOR",10, date "1973-04-27", 2300, NULL, 20); 1 row created. SQL> insert into employees values(10,"Pink", "J", "SALESREP",null,date "1974-03-28", 2400, 0, 30); 1 row created. SQL> SQL> SQL> select job, ename

 2  ,      decode(greatest(msal,2500),2500,"cheap","expensive") as class
 3  from   employees
 4  where  bdate <date "1964-01-01"
 5  order  by decode(job,"DIRECTOR",1,
 6                       "MANAGER",2,
 7                       3);

no rows selected SQL> SQL> drop table employees; Table dropped.</source>


decode column data to output more meaningful information

   <source lang="sql">

SQL> create table gift(

 2           gift_id                integer         primary key
 3          ,emp_id                integer
 4          ,register_date              date not null
 5          ,total_price        number(7,2)
 6          ,deliver_date           date
 7          ,deliver_time           varchar2(7)
 8          ,payment        varchar2(2)
 9          ,emp_no                 number(3,0)
10          ,deliver_name           varchar2(35)
11          ,message        varchar2(100)
12  );

Table created. SQL> SQL> insert into gift(gift_id,emp_id,register_date,total_price,deliver_date,deliver_time,payment,emp_no,deliver_name,message)values

 2                 (1,1,"14-Feb-1999", 123.12, "14-Feb-1999", "12 noon", "CA",1, null, "Happy Birthday to you");

1 row created. SQL> insert into gift(gift_id ,emp_id ,register_date ,total_price ,deliver_date ,deliver_time ,payment ,emp_no,deliver_name ,message)values

 2                 (2,1,"14-Feb-1999", 50.98, "14-feb-1999", "1 pm", "CA",7, "name1", "Happy Birthday");

1 row created. SQL> insert into gift(gift_id ,emp_id ,register_date ,total_price ,deliver_date ,deliver_time,payment ,emp_no,deliver_name ,message )values

 2                 (3, 2,"14-Feb-1999", 35.99, "14-feb-1999", "1 pm", "VS",2, "Tom", "Happy Birthday");

1 row created. SQL> insert into gift(gift_id ,emp_id ,register_date ,total_price ,deliver_date ,deliver_time,payment ,emp_no,deliver_name ,message )values

 2                 (4, 2,"14-Feb-1999", 19.95, "14-feb-1999", "5 pm", "CA",2, "Mary", "Happy Birthday");

1 row created. SQL> insert into gift(gift_id ,emp_id ,register_date ,total_price ,deliver_date ,deliver_time,payment ,emp_no,deliver_name ,message)values

 2                 (5, 6,"4-mar-1999", 10.95, "5-mar-1999", "4:30 pm", "VS", 2, "Jack", "Happy Birthday");

1 row created. SQL> SQL> SQL> SQL> select gift_id, decode(payment,

 2  "VS", "VISA Card Standard",
 3  "VG", "VISA Gold Card",
 4  "AX", "American Express",
 5  "MC", "Master Card",
 6  "DI", "Discover Card",
 7  "CA", "Cash",
 8  "CK", "Check",
 9  "Unknown")
10    from gift ;
  GIFT_ID DECODE(PAYMENT,"VS

------------------
        1 Cash
        2 Cash
        3 VISA Card Standard
        4 Cash
        5 VISA Card Standard

5 rows selected. SQL> SQL> SQL> drop table gift; Table dropped.</source>


DECODE in the GROUP BY clause

   <source lang="sql">

SQL> SQL> create table emp(

 2           emp_no                 integer         primary key
 3          ,lastname               varchar2(20)    not null
 4          ,firstname              varchar2(15)    not null
 5          ,midinit                varchar2(1)
 6          ,street                 varchar2(30)
 7          ,city                   varchar2(20)
 8          ,state                  varchar2(2)
 9          ,zip                    varchar2(5)
10          ,shortZipCode           varchar2(4)
11          ,area_code              varchar2(3)
12          ,phone                  varchar2(8)
13          ,salary                 number(5,2)
14          ,birthdate              date
15          ,startDate              date
16          ,title                  varchar2(20)
17          ,dept_no                integer
18          ,mgr                    integer
19          ,region                 number
20          ,division               number
21          ,total_sales            number
22  );

Table created. SQL> SQL> -- emp Table Inserts: SQL> insert into emp(emp_no, lastname, firstname, midinit, street, city, state, zip,shortZipCode, area_code, phone, birthdate, title)values

 2                      (1,"Z","Joy","R","1 Ave","New York","NY","12122","2333","212","200-1111","12-nov-1976","President");

1 row created. SQL> SQL> SQL> create or replace view avg_Sal

 2  as select trunc(avg(salary)) avg_sal
 3  from emp
 4  /

View created. SQL> SQL> SQL> select

 2  decode(  sign( (salary - avg_sal ) ),
 3       1, "> Average of " || to_char(avg_sal, "99.99") ,
 4       0, "= Average of " || to_char(avg_sal, "99.99"),
 5          -1, "< Average of " || to_char(avg_sal, "99.99")  ) sal_desc,
 6   count(*)
 7  from emp, avg_sal
 8  group by
 9  decode(  sign( (salary - avg_sal ) ),
10       1, "> Average of " || to_char(avg_sal, "99.99") ,
11       0, "= Average of " || to_char(avg_sal, "99.99"),
12          -1, "< Average of " || to_char(avg_sal, "99.99")  )
13  /
                            1

1 row selected. SQL> SQL> drop table emp; Table dropped.</source>


Demo range comparison with DECODE

   <source lang="sql">

SQL> SQL> create table emp(

 2           emp_no                 integer         primary key
 3          ,lastname               varchar2(20)    not null
 4          ,firstname              varchar2(15)    not null
 5          ,midinit                varchar2(1)
 6          ,street                 varchar2(30)
 7          ,city                   varchar2(20)
 8          ,state                  varchar2(2)
 9          ,zip                    varchar2(5)
10          ,shortZipCode           varchar2(4)
11          ,area_code              varchar2(3)
12          ,phone                  varchar2(8)
13          ,salary                 number(5,2)
14          ,birthdate              date
15          ,startDate              date
16          ,title                  varchar2(20)
17          ,dept_no                integer
18          ,mgr                    integer
19          ,region                 number
20          ,division               number
21          ,total_sales            number
22  );

Table created. SQL> SQL> -- emp Table Inserts: SQL> insert into emp(emp_no, lastname, firstname, midinit, street, city, state, zip,shortZipCode, area_code, phone, birthdate, title)values

 2                      (1,"Z","Joy","R","1 Ave","New York","NY","12122","2333","212","200-1111","12-nov-1976","President");

1 row created. SQL> SQL> create or replace view avg_Sal

 2  as select trunc(avg(salary)) avg_sal
 3  from emp
 4  /

View created. SQL> SQL> select lastname, salary,

 2  decode(  sign( salary - avg_sal ),
 3       1, "> Average of " || to_char(avg_sal, "99.99") ,
 4       0, "= Average of " || to_char(avg_sal, "99.99"),
 5          -1, "< Average of " || to_char(avg_sal, "99.99")  ) sal_desc
 6  from emp, avg_sal
 7  /

Z 1 row selected. SQL> SQL> drop table emp; Table dropped.</source>


Pass multiple search and result parameters to DECODE()

   <source lang="sql">

SQL> SQL> 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> 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> SELECT id,

 2  DECODE(id, 1, "A",
 3             2, "B",
 4             3, "C",
 5             4, "D",
 6                "Default")
 7  FROM employee;

ID DECODE(


-------

01 A 02 B 03 C 04 D 05 Default 06 Default 07 Default 08 Default 8 rows selected. SQL> SQL> SQL> SQL> SQL> -- clean the table SQL> drop table Employee

 2  /

Table dropped. SQL></source>


SELECT DECODE( 3)

   <source lang="sql">

SQL> SELECT DECODE(1, 2, 1, 3)

 2  FROM dual;

DECODE(1,2,1,3)


             3

SQL> SQL></source>


The null may be made more explicit with a DECODE statement

   <source lang="sql">

SQL> 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("20060

725","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("19860

221","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("19900

315","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("19990

421","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("19980

808","YYYYMMDD"), 2334.78, NULL,"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("19960

104","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("19980

212","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("20020

415","YYYYMMDD"), 1232.78,NULL, "Tester")

 3  /

1 row created. SQL> SQL> 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 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 Tester 8 rows selected. SQL> SQL> SQL> SQL> SELECT count(*), DECODE(city,null,"Null",city) CITY

 2  FROM employee
 3  GROUP BY city;
 COUNT(*) CITY

----------
        2 Null
        2 New York
        1 Toronto
        3 Vancouver

SQL> SQL> -- clean the table SQL> drop table Employee

 2  /

Table dropped. SQL> SQL> SQL></source>


Use decode as if statement and output "high" or "low"

   <source lang="sql">

SQL> create table emp

 2  ( empno      NUMBER(4)    constraint E_PK primary key
 3  , ename      VARCHAR2(8)
 4  , init       VARCHAR2(5)
 5  , job        VARCHAR2(8)
 6  , mgr        NUMBER(4)
 7  , bdate      DATE
 8  , sal        NUMBER(6,2)
 9  , comm       NUMBER(6,2)
10  , deptno     NUMBER(2)    default 10
11  ) ;

Table created. SQL> insert into emp values(1,"Tom","N", "Coder", 13,date "1965-12-17", 800 , NULL, 20); 1 row created. SQL> insert into emp values(2,"Jack","JAM", "Tester",6,date "1961-02-20", 1600, 300, 30); 1 row created. SQL> insert into emp values(3,"Wil","TF" , "Tester",6,date "1962-02-22", 1250, 500, 30); 1 row created. SQL> insert into emp values(4,"Jane","JM", "Designer", 9,date "1967-04-02", 2975, NULL, 20); 1 row created. SQL> insert into emp values(5,"Mary","P", "Tester",6,date "1956-09-28", 1250, 1400, 30); 1 row created. SQL> insert into emp values(6,"Black","R", "Designer", 9,date "1963-11-01", 2850, NULL, 30); 1 row created. SQL> insert into emp values(7,"Chris","AB", "Designer", 9,date "1965-06-09", 2450, NULL, 10); 1 row created. SQL> insert into emp values(8,"Smart","SCJ", "Coder", 4,date "1959-11-26", 3000, NULL, 20); 1 row created. SQL> insert into emp values(9,"Peter","CC", "Designer",NULL,date "1952-11-17", 5000, NULL, 10); 1 row created. SQL> insert into emp values(10,"Take","JJ", "Tester",6,date "1968-09-28", 1500, 0, 30); 1 row created. SQL> insert into emp values(11,"Ana","AA", "Coder", 8,date "1966-12-30", 1100, NULL, 20); 1 row created. SQL> insert into emp values(12,"Jane","R", "Manager", 6,date "1969-12-03", 800 , NULL, 30); 1 row created. SQL> insert into emp values(13,"Fake","MG", "Coder", 4,date "1959-02-13", 3000, NULL, 20); 1 row created. SQL> insert into emp values(14,"Mike","TJA","Manager", 7,date "1962-01-23", 1300, NULL, 10); 1 row created. SQL> SQL> SQL> select job, ename

 2  ,      decode(greatest(sal,2500)
 3               ,2500,"cheap","expensive") as class
 4  from   emp
 5  where  bdate <date "1964-01-01"
 6  order  by decode(job,"Designer",1,"Designer",2,3);

JOB ENAME CLASS


-------- ---------

Designer Black expensive Designer Peter expensive Tester Mary cheap Manager Mike cheap Coder Smart expensive Coder Fake expensive Tester Wil cheap Tester Jack cheap 8 rows selected. SQL> SQL> SQL> drop table emp; Table dropped.</source>


Use decode create dynamic select statement

   <source lang="sql">

SQL> CREATE TABLE EMP(

 2      EMPNO NUMBER(4) NOT NULL,
 3      ENAME VARCHAR2(10),
 4      JOB VARCHAR2(9),
 5      MGR NUMBER(4),
 6      HIREDATE DATE,
 7      SAL NUMBER(7, 2),
 8      COMM NUMBER(7, 2),
 9      DEPTNO NUMBER(2)
10  );

Table created. SQL> SQL> INSERT INTO EMP VALUES(7369, "SMITH", "CLERK", 7902,TO_DATE("17-DEC-1980", "DD-MON-YYYY"), 800, NULL, 20); 1 row created. SQL> INSERT INTO EMP VALUES(7499, "ALLEN", "SALESMAN", 7698,TO_DATE("20-FEB-1981", "DD-MON-YYYY"), 1600, 300, 30); 1 row created. SQL> INSERT INTO EMP VALUES(7521, "WARD", "SALESMAN", 7698,TO_DATE("22-FEB-1981", "DD-MON-YYYY"), 1250, 500, 30); 1 row created. SQL> INSERT INTO EMP VALUES(7566, "JONES", "MANAGER", 7839,TO_DATE("2-APR-1981", "DD-MON-YYYY"), 2975, NULL, 20); 1 row created. SQL> INSERT INTO EMP VALUES(7654, "MARTIN", "SALESMAN", 7698,TO_DATE("28-SEP-1981", "DD-MON-YYYY"), 1250, 1400, 30); 1 row created. SQL> INSERT INTO EMP VALUES(7698, "BLAKE", "MANAGER", 7839,TO_DATE("1-MAY-1981", "DD-MON-YYYY"), 2850, NULL, 30); 1 row created. SQL> INSERT INTO EMP VALUES(7782, "CLARK", "MANAGER", 7839,TO_DATE("9-JUN-1981", "DD-MON-YYYY"), 2450, NULL, 10); 1 row created. SQL> INSERT INTO EMP VALUES(7788, "SCOTT", "ANALYST", 7566,TO_DATE("09-DEC-1982", "DD-MON-YYYY"), 3000, NULL, 20); 1 row created. SQL> INSERT INTO EMP VALUES(7839, "KING", "PRESIDENT", NULL,TO_DATE("17-NOV-1981", "DD-MON-YYYY"), 5000, NULL, 10); 1 row created. SQL> INSERT INTO EMP VALUES(7844, "TURNER", "SALESMAN", 7698,TO_DATE("8-SEP-1981", "DD-MON-YYYY"), 1500, 0, 30); 1 row created. SQL> INSERT INTO EMP VALUES(7876, "ADAMS", "CLERK", 7788,TO_DATE("12-JAN-1983", "DD-MON-YYYY"), 1100, NULL, 20); 1 row created. SQL> INSERT INTO EMP VALUES(7900, "JAMES", "CLERK", 7698,TO_DATE("3-DEC-1981", "DD-MON-YYYY"), 950, NULL, 30); 1 row created. SQL> INSERT INTO EMP VALUES(7902, "FORD", "ANALYST", 7566,TO_DATE("3-DEC-1981", "DD-MON-YYYY"), 3000, NULL, 20); 1 row created. SQL> INSERT INTO EMP VALUES(7934, "MILLER", "CLERK", 7782,TO_DATE("23-JAN-1982", "DD-MON-YYYY"), 1300, NULL, 10); 1 row created. SQL> SQL> create or replace function get_value_static( p_empno in number, p_cname in varchar2 ) return varchar2

 2  as
 3      l_value  varchar2(4000);
 4  begin
 5      select decode( upper(p_cname),
 6                    "ENAME", ename,
 7                    "EMPNO", empno,
 8                    "HIREDATE", to_char(hiredate,"yyyymmddhh24miss"))
 9        into l_value
10        from emp
11       where empno = p_empno;
12
13      return l_value;
14  end;
15  /

Function created. SQL> SQL> SQL> SQL> drop table emp; Table dropped.</source>


Use Decode in table column

   <source lang="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> 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> SQL> SELECT id,

 2     DECODE(id, "01", "id is 1",
 3                      "id is not 1")
 4  FROM employee;

ID DECODE(ID,"


-----------

01 id is 1 02 id is not 1 03 id is not 1 04 id is not 1 05 id is not 1 06 id is not 1 07 id is not 1 08 id is not 1 8 rows selected. SQL> SQL> SQL> -- clean the table SQL> drop table Employee

 2  /

Table dropped. SQL> SQL></source>


Using the DECODE() Function

DECODE(value, search_value, result, default_value) compares value with search_value. If the values are equal, DECODE() returns result, otherwise default_value is returned. DECODE() allows you to perform if-then-else logic in SQL without having to use PL/SQL.



   <source lang="sql">

SQL> SELECT DECODE(1, 1, 2, 3)

 2  FROM dual;

DECODE(1,1,2,3)


             2

SQL></source>