oracle笔记（十三）条件表达式

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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