–decode(条件,值1,返回值1,值2,返回值2,…值n,返回值n,缺省值)

SELECT DECODE(TEMP.SCORE,

‘A’,

‘90-100’,

‘B’,

‘80-89’,

‘C’,

‘70-79’,

‘D’,

‘60-69’,

‘E’,

‘0-59’,

‘其他’) AS XXX

FROM (SELECT ‘A’ SCORE FROM DUAL) TEMP

–结果：’90-100’

–decode(条件，比较值，值1，值2）

–当条件的值等于比较值时，该函数返回值1，否则返回值2

SELECT DECODE(NULL,

TEMP.A,

DECODE(NULL, TEMP.B, DECODE(NULL, TEMP.C, ”, TEMP.C), TEMP.B),

TEMP.A) AS XXX

FROM (SELECT NULL A, ‘B’ B, ‘C’ C FROM DUAL) TEMP

SELECT DECODE(TEMP.A,

NULL,

DECODE(TEMP.B, NULL, DECODE(TEMP.C, NULL, ”, TEMP.C), TEMP.B),

TEMP.A) AS XXX

FROM (SELECT NULL A, NULL B, ‘C’ C FROM DUAL) TEMP