如何在postgres中使用CTE重写此查询

Question

我的查询如下所示

UPDATE tname 
SET cname1 = TRIM(TRAILING 'xxx' from l_name), 
    cname2 = f_name, 
    cname3 = TRIM(TRAILING 'xxx' from l_name)  
where tname.last_name ilike '%xxxyyy%' and cid in (zzzz);

如何在Postgres中使用CTE重写此内容？这样我在查询中两次不重复使用trim功能？

Answer 1

尝试如下

with cte as
(
  select TRIM(TRAILING 'xxx' from l_name) as n1,
f_name
from tname where tname.last_name like '%xxxyyy%' and cid in (zzzz)
) update tname 
 set cname1=n1,
cname2=cte.f_name,
cname3=n1 
from cte       
  where t1.f_name=cte.f_name

Answer 2

我不担心。但是如果你有一个主键，你可以使用：

UPDATE tname 
    SET cname1 = tt.trimmed_l_name, 
        cname2 = tname.f_name, 
        cname3 = tt.trimmed_l_name 
FROM (SELECT tn.*, TRIM(TRAILING 'xxx' FROM l_name) as trimmed_l_name
      FROM tname tn 
     ) tt
     ON tname.pk = tn.pk
WHERE tname.last_name ilike '%xxxyyy%' and tname.cid in (zzzz);