postgresql - 使用 CASE WHEN 选择两列

Question

我想选择三列(id_produkt、313、314)所以我尝试了:

select id_produkt, 
 case when bp_stan_produkt.id_stan_produkt = 313
 then 'TAK'
 else 'NIE' 
 end as "313"
 from bp_stan_produkt where data_do is not null

 union 

 select id_produkt, 
 case when bp_stan_produkt.id_stan_produkt = 314
 then 'TAK'
 else 'NIE'
 end as "314"
 from bp_stan_produkt where data_do is not null

但它只返回两列:id_produkt 和 313。如何获得带有别名的三列？

Answer 1

试试这个 SQL 代码

select id_produkt, 
case when id_stan_produkt = 313 then 'TAK' 
else 'NIE'
end  as "313",
case when id_stan_produkt = 314 then 'TAK' 
else 'NIE'
end  as "314"
 from bp_stan_produkt where data_do is null