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10.Oracle中decode函数

news 2025/7/26 8:26:52

【函数格式】：
decode (

expression,

condition_01, result_01,

condition_02, result_02,

......,

condition_n, result_n,

result_default)

【函数说明】：
若表达式expression值与condition_01值匹配，则返回result_01，若不匹配，则继续判断；
若表达式expression值与condition_02值匹配，则返回result_02，若不匹配，则继续判断；
以此类推，若表达式expression值condition_n值匹配，则返回result_n，若不匹配，则继续判断；
若表达式expression值与以上所有的condition都不匹配，则返回默认值result_default，若省略result_default参数，则返回null

示例

insert into T_STUDENT_GRADE (studentid, classid, engilshgrade, chinesegrade, mathgrade, gradelevel)
values ('stud01', 'clas01', 60, 70, 80, 'C');
insert into T_STUDENT_GRADE (studentid, classid, engilshgrade, chinesegrade, mathgrade, gradelevel)
values ('stud02', 'clas01', 75, 85, 95, 'B');
insert into T_STUDENT_GRADE (studentid, classid, engilshgrade, chinesegrade, mathgrade, gradelevel)
values ('stud03', 'clas01', 80, 90, 100, 'A');
insert into T_STUDENT_GRADE (studentid, classid, engilshgrade, chinesegrade, mathgrade, gradelevel)
values ('stud04', 'clas02', 55, 60, 65, 'D');
insert into T_STUDENT_GRADE (studentid, classid, engilshgrade, chinesegrade, mathgrade, gradelevel)
values ('stud05', 'clas02', 40, 50, 60, 'E');
insert into T_STUDENT_GRADE (studentid, classid, engilshgrade, chinesegrade, mathgrade, gradelevel)
values ('stud06', 'clas02', 100, 100, 100, 'S');

查询表中数据，查询结果如下所示

1.将指定数据翻译或转换成其他形式

sql语句如下：

select GradeLevel,decode(GradeLevel,'S','完美','A','优秀','B','良好','C','较好','D','及格','E','不及格','其他') as gradeRemark from T_STUDENT_GRADE

返回结果如下图所示：

2.对指定数据按指定范围进行分段

sql语句如下：

select mathgrade,decode(mathgrade,100,'完美',decode(sign(mathgrade-90),1,'优秀',0,'优秀',-1,decode(sign(mathgrade-80),1,'良好',0,'良好',-1,decode(sign(mathgrade-70),1,'较好',0,'较好',-1,decode(sign(mathgrade-60),'1','及格',0,'及格',-1,'不及格'))))) as mathGradeRemark from T_STUDENT_GRADE

返回结果如下图所示：