DECODE
The format:
decode( expression , search , result [, search2 , result2]... [, default] )It can be mapped to:
if expression = search
return result
else if expression = search2
return result2
...
else if expression = searchN
return resultN
else
return default;
SQL> select decode(1,1,'One',
2 2,'Two',
3 'Unknown') from dual;
DEC
---
One
SQL>
Using the decode function to translate employee numbers:
CREATE TABLE EMP (EMPNO NUMBER(4) NOT NULL,
ENAME VARCHAR2(10),
JOB VARCHAR2(9),
SAL NUMBER(7, 2),
DEPTNO NUMBER(2));
INSERT INTO EMP VALUES (1, 'SMITH', 'CLERK', 800, 20);
INSERT INTO EMP VALUES (2, 'ALLEN', 'SALESMAN', 1600, 30);
INSERT INTO EMP VALUES (3, 'WARD', 'SALESMAN', 1250, 30);
INSERT INTO EMP VALUES (4, 'JONES', 'MANAGER', 2975, 20);
INSERT INTO EMP VALUES (5, 'MARTIN','SALESMAN', 1250, 30);
INSERT INTO EMP VALUES (6, 'BLAKE', 'MANAGER', 2850, 30);
INSERT INTO EMP VALUES (7, 'CLARK', 'MANAGER', 2850, 10);
INSERT INTO EMP VALUES (8, 'SCOTT', 'ANALYST', 3000, 20);
INSERT INTO EMP VALUES (9, 'KING', 'PRESIDENT',3000, 10);
INSERT INTO EMP VALUES (10,'TURNER','SALESMAN', 1500, 30);
INSERT INTO EMP VALUES (11,'ADAMS', 'CLERK', 1500, 20);
SQL> select empno, decode(empno, 1, 'One',
2 2,'Two',
3 'Other')
4 from emp;
EMPNO DECOD
---------- -----
1 One
2 Two
3 Other
4 Other
5 Other
6 Other
7 Other
8 Other
9 Other
10 Other
11 Other
11 rows selected.
SQL>
SQL>
SQL>
SQL>