Updating a table using CASE and conditions (postgresql)

Question

i have the tables ::

CREATE TABLE emp1
(
  eid integer NOT NULL,
  ename character varying(20),
  sid integer,
  ssid integer,
  CONSTRAINT pk_eid PRIMARY KEY (eid)
);

CREATE TABLE leave_type
(
  eid integer,
  lid integer,
  lnum integer,
  emp_bal integer,
  sno serial NOT NULL,
  CONSTRAINT pk_sno PRIMARY KEY (sno),
  CONSTRAINT fk_eid FOREIGN KEY (eid)
      REFERENCES emp1 (eid) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION
);//emp_bal-->employee balance leaves which is considered as 8

CREATE TABLE result
(
  eid integer,
  lid integer,
  sd date,
  ed date,
  sida boolean,
  ssida boolean,
  rsno serial NOT NULL,
  CONSTRAINT pk_rsno PRIMARY KEY (rsno)
);

INSERTED DATA IS

emp1
-----
 eid | ename | sid | ssid
-----+-------+-----+------
   1 | a     |   2 |    8
   3 | c     |   4 |    9
   2 | b     |   3 |    8
   4 | d     |   2 |    8
   5 | e     |   2 |    8
   6 | f     |   4 |    9

(6 rows)

leave_type
----------
 eid | lid | lnum | emp_bal | sno
-----+-----+------+---------+-----
   1 |   0 |    1 |       8 |   1
   3 |   0 |    1 |       8 |   2
   5 |   0 |    1 |       8 |   3
   1 |   1 |    1 |       8 |   4
   1 |   2 |    2 |       8 |   5
(5 rows)

result
-------
 eid | lid |     sd     |     ed     | sida | ssida | rsno
-----+-----+------------+------------+------+-------+------
   1 |   0 | 2013-01-01 | 2013-01-01 | t    | f     |    1
   3 |   0 | 2013-01-09 | 2013-01-09 | t    | f     |    2
   5 |   0 | 2013-01-11 | 2013-01-11 | t    | f     |    3
   1 |   1 | 2013-02-14 | 2013-02-14 | t    | f     |    4
   1 |   2 | 2013-03-15 | 2013-03-16 | f    | t     |    5
(5 rows)

Query :

I want a approval table to be updated

CREATE TABLE approval
    (
      eid integer,
      lid integer,
      asid integer,
      bal integer
    );

as the output

      eid | lid | sid |bal
     -----+-----+---+--
       1 |   0 | 2 | 7
       3 |   0 | 4 | 7
       5 |   0 | 2 | 7
       1 |   1 | 2 | 6
       1 |   2 | 8 | 4
    (5 rows)

conditions:: i tried this query for getting the sid into approval table as stated below::

CASE WHEN r.sida='t' 
  THEN (update approval set a.asid=e.sid where a.eid=e.eid from emp1 e,approval a)
WHEN r.ssida='t'
  THEN (update approval set a.asid=e.ssid where a.eid=e.eid from emp1 e,approval a) 
ELSE 0
END

i want even the balance column should be updated basing on sid verification i.e..,

CASE if r.sida='t' then bal=emp1.emp_bal-1 and emp_bal in emp1 should be updated to latest value of bal from approval else if r.ssida='t' then bal=emp_bal-2 and emp_bal in emp1 should be updated to latest value of bal from approval

Is there a way to solve this?

finally i want to see all the employee leaves which are approved and who approved it and there balance leaves left!!

Full details are in the [SQL FIDDLE] (http://sqlfiddle.com/#!12/3e6a7/18)

Solution

You are doing wrong.

Use Case Statement witin a Update Statement instead of using Update Statement Within Case Statement.

Like

Update **Table**
Set **Col1**= 

Case when **Col10=1** then 5

else case when **Col10=2** THEN 6

**ELSE 10** END  
**ELSE 15** END