postgresql function 中的流程控制一（判断）

最帅dba工作笔记 2021-04-22

1488

同其他变成语言一样，plpgsql也遵循流程控制的三要素：顺序，分支，循环

环境需要创建emp表：

create table EMP(
EMPNO numeric(4) not null,
ENAME varchar(10),
JOB varchar(9),
MGR numeric(4),
HIREDATE date,
SAL numeric(7 ),
COMM numeric(7 ),
DEPTNO numeric(2));
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7369, 'SMITH', 'CLERK', 7902, to_date('1980-12-17', 'YYYY-MM-DD'), 800, null, 20);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7499, 'ALLEN', 'SALESMAN', 7698, to_date('1981-02-20', 'YYYY-MM-DD'), 1600, 300, 30);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7521, 'WARD', 'SALESMAN', 7698, to_date('1981-02-22', 'YYYY-MM-DD'), 1250, 500, 30);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7566, 'JONES', 'MANAGER', 7839, to_date('1981-04-02', 'YYYY-MM-DD'), 2975, null, 20);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7654, 'MARTIN', 'SALESMAN', 7698, to_date('1981-09-28', 'YYYY-MM-DD'), 1250, 1400, 30);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7698, 'BLAKE', 'MANAGER', 7839, to_date('1981-05-01', 'YYYY-MM-DD'), 2850, null, 30);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7782, 'CLARK', 'MANAGER', 7839, to_date('1981-06-09', 'YYYY-MM-DD'), 2450, null, 10);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7788, 'SCOTT', 'ANALYST', 7566, to_date('1987-04-19', 'YYYY-MM-DD'), 3000, null, 20);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7839, 'KING', 'PRESIDENT', null, to_date('1981-11-17', 'YYYY-MM-DD'), 5000, null, 10);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7844, 'TURNER', 'SALESMAN', 7698, to_date('1981-09-08', 'YYYY-MM-DD'), 1500, 0, 30);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7876, 'ADAMS', 'CLERK', 7788, to_date('1987-05-23', 'YYYY-MM-DD'), 1100, null, 20);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7900, 'JAMES', 'CLERK', 7698, to_date('1981-12-03', 'YYYY-MM-DD'), 950, null, 30);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7902, 'FORD', 'ANALYST', 7566,to_date('1981-12-02', 'YYYY-MM-DD'), 3000, null, 20);
insert into EMP (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
values (7934, 'MILLER', 'CLERK', 7782, to_date('1982-01-23', 'YYYY-MM-DD'), 1300, null, 10);
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条件判断：

常用的有if和case两种语法

if 有三种形式:

if ... then ... end if;
if ... then ... else ... end if;
if ... then ... else if ... then ... else ... end if;
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case 有两种形式：

case ... when ... then ... else ... end case;
case when ... then ... else ... end case;
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案例:

当员工工资少于1500的提示出多加工资，当员工工资多于1500的时候，提示少加工资

create or replace function incre_sal_fun(emp_name varchar)
returns void
as $$
declare
emp_sal numeric;
begin
   select sal into emp_sal from emp where ename=emp_name;
     if emp_sal is null then
         raise notice '此员工不是本公司员工';
     elseif emp_sal < 1500 then
         raise notice '此员工应该多涨工资';
     else
         raise notice '此员工应该少涨工资';
     end if;       
end;
$$ language plpgsql;
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表中数据

vastbase=# select * from emp;
empno | ename  |    job    | mgr  |      hiredate       | sal  | comm | deptno
-------+--------+-----------+------+---------------------+------+------+--------
  7369 | SMITH  | CLERK     | 7902 | 1980-12-17 00:00:00 |  800 |      |     20
  7499 | ALLEN  | SALESMAN  | 7698 | 1981-02-20 00:00:00 | 1600 |  300 |     30
  7521 | WARD   | SALESMAN  | 7698 | 1981-02-22 00:00:00 | 1250 |  500 |     30
  7566 | JONES  | MANAGER   | 7839 | 1981-04-02 00:00:00 | 2975 |      |     20
  7654 | MARTIN | SALESMAN  | 7698 | 1981-09-28 00:00:00 | 1250 | 1400 |     30
  7698 | BLAKE  | MANAGER   | 7839 | 1981-05-01 00:00:00 | 2850 |      |     30
  7782 | CLARK  | MANAGER   | 7839 | 1981-06-09 00:00:00 | 2450 |      |     10
  7788 | SCOTT  | ANALYST   | 7566 | 1987-04-19 00:00:00 | 3000 |      |     20
  7839 | KING   | PRESIDENT |      | 1981-11-17 00:00:00 | 5000 |      |     10
  7844 | TURNER | SALESMAN  | 7698 | 1981-09-08 00:00:00 | 1500 |    0 |     30
  7876 | ADAMS  | CLERK     | 7788 | 1987-05-23 00:00:00 | 1100 |      |     20
  7900 | JAMES  | CLERK     | 7698 | 1981-12-03 00:00:00 |  950 |      |     30
  7902 | FORD   | ANALYST   | 7566 | 1981-12-02 00:00:00 | 3000 |      |     20
  7934 | MILLER | CLERK     | 7782 | 1982-01-23 00:00:00 | 1300 |      |     10
(14 rows)
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结果：

vastbase=# select incre_sal_fun('ADAMS');
NOTICE:  此员工应该多涨工资
CONTEXT:  referenced column: incre_sal_fun
incre_sal_fun
---------------
(1 row)
vastbase=# select incre_sal_fun('SCOTT');
NOTICE:  此员工应该少涨工资
CONTEXT:  referenced column: incre_sal_fun
incre_sal_fun
---------------
(1 row)
vastbase=# select incre_sal_fun('FORD');
NOTICE:  此员工应该少涨工资
CONTEXT:  referenced column: incre_sal_fun
incre_sal_fun
---------------
(1 row)
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CASE 条件

传入一个参数，判断这个数是不是1,2。

第一种：

case ... when ... else ... end case;
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示例:

create or replace function case_fun(x numeric)
returns void as $$
declare
msg varchar;
begin
    case x when 1,2 then
        msg:='maybe 1 or 2';
    else
        msg:=' is not 1 or 2';
    end case;
        raise notice 'the num %',msg;
end;
$$ language plpgsql;
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结果：

vastbase=# select case_fun(1);
NOTICE:  the num maybe 1 or 2
CONTEXT:  referenced column: case_fun
case_fun
----------
(1 row)
vastbase=# select case_fun(3);
NOTICE:  the num  is not 1 or 2
CONTEXT:  referenced column: case_fun
case_fun
----------
(1 row)
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第二种：

case when ... else ... end case;
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示例：

create or replace function case_fun1(num numeric)
returns void as $$
declare
msg varchar;
begin
   case when num in (1,2) then msg :='is 1,2';
   else msg :='is not in value';
   end case ;
   raise notice 'the number %',msg;
end;
$$ language plpgsql;
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结果：

vastbase=# select case_fun1(3);
NOTICE:  the number is not in value
CONTEXT:  referenced column: case_fun1
case_fun1
-----------
(1 row)
vastbase=# select case_fun1(2);
NOTICE:  the number is 1,2
CONTEXT:  referenced column: case_fun1
case_fun1
-----------
(1 row)
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THAT'S ALL

BY CUI PEACE!!!

postgresql

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postgresql function 中的流程控制一（判断）

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