oracle笔记（十三）条件表达式
条件表达式 ：IF-THEN-ELSE 逻辑
CASE expr WHEN comparison_expr1 THEN return_expr1
[WHEN comparison_expr2 THEN return_expr2
WHEN comparison_exprn THEN return_exprn
ELSE else_expr]
END
DECODE(col|expression, search1, result1
[, search2, result2,...,]
[, default])
//为职位是Manager的员工发放5000元的奖金
SQL> select ename,job,case job when 'MANAGER' then nvl(sal,0)+5000 end as "工资" from emp;
//员工的工资
SQL> select ename ,job,
2 case job when 'MANAGER' then nvl(sal,0)+5000+nvl(comm,0)
3 else nvl(sal,0)+nvl(comm,0)
4 end
5 from emp;
//改写成 decode的写法
SQL> select ename,job
2 ,decode(job,'MANAGER', nvl(sal,0)+5000+nvl(comm,0),
3 'CLERK',nvl(sal,0)+nvl(comm,0)+200,
4 nvl(sal,0)+nvl(comm,0)) as "工资"
5 from emp;
//作业： 当员工为Manger 加5000员 当员工为SALESMAN 加1000 当员工为 clerk加500
SQL> select ename,job,case job when 'MANAGER' then nvl(sal,0)+5000+nvl(comm,0)
when 'SALESMAN' then nvl(sal,0)+1000+nvl(comm,0)
when 'CLERK'then nvl(sal,0)+500+nvl(comm,0)
else nvl(sal,0)+nvl(comm,0)
end from emp;
ENAME JOB CASEJOBWHEN'MANAGER'THENNVL(SA
---------- --------- ------------------------------
SMITH CLERK 1300
ALLEN SALESMAN 2900
WARD SALESMAN 2750
JONES MANAGER 7975
MARTIN SALESMAN 3650
BLAKE MANAGER 7850
CLARK MANAGER 7450
SCOTT ANALYST 3000
KING PRESIDENT 5000
TURNER SALESMAN 2500
ADAMS CLERK 1600
JAMES CLERK 1450
FORD ANALYST 3000
MILLER CLERK 1800
kou%kou% 0
xiao%lin 0
xiao%lin 0
17 rows selected
SQL> select ename,job,decode(
2 job,'MANAGER',nvl(sal,0)+5000+nvl(comm,0),
3 'SALESMAN',nvl(sal,0)+1000+nvl(comm,0),
4 'CLERK',nvl(sal,0)+500+nvl(comm,0))
5 as "工资" from emp;
ENAME JOB 工资
---------- --------- ----------
SMITH CLERK 1300
ALLEN SALESMAN 2900
WARD SALESMAN 2750
JONES MANAGER 7975
MARTIN SALESMAN 3650
BLAKE MANAGER 7850
CLARK MANAGER 7450
SCOTT ANALYST
KING PRESIDENT
TURNER SALESMAN 2500
ADAMS CLERK 1600
JAMES CLERK 1450
FORD ANALYST
MILLER CLERK 1800
kou%kou%
xiao%lin
xiao%lin
17 rows selected