PostgreSQL , 案例时间

如何解决PostgreSQL , 案例时间

我有疑问

select case
  when (status = 'MENANG' is null ) then '0'
  when (status = 'KALAH' is null) then '0'
  when (status = 'PROSES' is null) then '0'
  when (status = 'BATAL' is null) then '0'
  when (status = 'MUNDUR' is null) then '0'
  else status 
  end as data_status,count(a.kode_barang) as total 
  from tbl barang 
  group by status

这里我有一个查询和一些状态， 这里我用count根据状态计算物品的数量

运行时，

data_status | jumlah (count)
KALAH              2
kosong             4
MENANG             2
PROSES             11

如何显示所有状态数据，包括值为0或null的状态数据

解决方法

如果您没有包含 status 的所有可能值的表，您可以使用 VALUES 列表和 LEFT JOIN：

select v.status,count(b.status) as total
from ( 
      values ('MENANG','KALAH','PROSES','BATAL','MUNDUR')
  ) as v(status)
  left join barang b on b.status = v.status
group by v.status

,

如果您在表格中有可用状态的列表，您只需要加入 LEFT OUTER JOIN

如果您的 list_of_status 表是：

create table list_of_status (status varchar);
insert into  list_of_status values('MENANG');
insert into  list_of_status values('KALAH');
insert into  list_of_status values('PROSES');
insert into  list_of_status values('BATAL');
insert into  list_of_status values('MUNDUR');

而您的 data_status 是

create table data_status (status varchar,kode_barang int);
insert into data_status values ('MENANG',3);
insert into data_status values ('KALAH',2);
insert into data_status values ('PROSES',3);
insert into data_status values ('MENANG',3);

SELECT 
list_of_status.STATUS,count(kode_barang) as total 
FROM list_of_status LEFT OUTER JOIN data_status ON list_of_status.STATUS= data_status.STATUS
group by list_of_status.STATUS

预期结果

 status | total 
--------+-------
 KALAH  |     1
 BATAL  |     0
 MENANG |     2
 PROSES |     1
 MUNDUR |     0
(5 rows)

如果您想要 list_of_status 表中的所有状态PLUS，data_status 中存在的任何其他状态，您可以使用 FULL_OUTER_JOIN 来实现。 >

例如如果我们在 data_status 中包含一行 TEST 状态在 list_of_status 中不可用

insert into data_status values ('TEST',5);

以下查询返回所需的结果，包括 TEST 行

select
COALESCE(list_of_status.STATUS,data_status.STATUS) STATUS,count(kode_barang) as total 
FROM list_of_status FULL OUTER JOIN data_status ON list_of_status.STATUS= data_status.STATUS
group by COALESCE(list_of_status.STATUS,data_status.STATUS)

结果：

 status | total 
--------+-------
 TEST   |     1
 MUNDUR |     0
 MENANG |     2
 PROSES |     1
 KALAH  |     1
 BATAL  |     0
(6 rows)