在 plpgsql 函数中访问 select 语句结果

Question

如何在 plpgsql 函数中访问 select 语句的结果以检查其内容？

我需要检查我使用的ilike 函数是否在我的people 表中返回任何匹配的演员。如果没有匹配项，我需要在“actor_details”表中返回“No matching name”，但如果有多个不同的值，我需要返回“Non-distinct actor name”之类的内容。

如果其中任何一个条件为真，我需要跳出函数并简单地在“actor_details”表中返回这些文本字符串。

在我的实际函数中，我需要在该语句之后附加几行文本，因此RETURNS table。

任何指针都会很棒。最后两行代码中定义的预期输出。

CREATE TABLE people (
    id integer NOT NULL,
    name text NOT NULL,
    year_born integer,
    year_died integer
);

insert into people (id, name, year_born, year_died) values
(20000007,  'Humphrey Bogart',  1899,   1957)
(20000008,  'Marlon Brando',    1924,   2004)
(20000009,  'Richard Burton',   1925,   1984)
(200000010, 'Richard Hunt',     1985,   NULL)

CREATE OR REPLACE FUNCTION actor_details(_pattern text) 
RETURNS table (actor_details text) 
AS $$

BEGIN
  select distinct concat(people.name, ' (', people.year_born, '-', people.year_died, ')') 
    into actor_details
  from people
  where people.name ilike('%' || _pattern || '%');
  
  --- THIS IS WHERE I NEED HELP
  IF (@@ROWCOUNT = 0) then
    select 'No matching name' into actor_details;
  ELSIF (@@ROWCOUNT > 1) then
    select 'Non-distinct actor name';
  END IF; 
  return;              


END
$$ 
LANGUAGE plpgsql;

select * from actor_details('xxyyzz'); ---<<< Should return 'No matching name' in a column titled actor_details
select * from actor_details('Richarch'); ---<<< Should return 'Non-distinct actor name' in a column titled actor_details

Answer 1

我建议在查询中进行聚合以获取 actor_details:

select (case when count(*) = 0
             then 'No matching name'
             when count(distinct concat(p.name, ' (', p.year_born, '-', p.year_died, ')')) > 1
             then 'Non-distinct actor name'
             else max(concat(p.name, ' (', p.year_born, '-', p.year_died, ')'))
        end)
into actor_details
from people p
where p.name ilike('%' || _pattern || '%');

那么查询之后就不需要任何额外的逻辑了。

Answer 2

您可以使用UNION ALL 和三个根据匹配数选择字符串的查询来做到这一点。你甚至不需要 PL/pgSQL。 （你想要一个只包含一个值的集合似乎很奇怪。简单地返回一个标量可能更有意义。）

CREATE
 OR REPLACE FUNCTION actor_details
                     (_pattern text) 
                     RETURNS table
                             (actor_details text) 
AS
$$
SELECT concat(people.name,
              ' (',
              people.year_born,
              '-',
              people.year_died,
              ')')
       FROM people
       WHERE people.name ILIKE '%' || _pattern || '%'
             AND (SELECT count(*)
                         FROM people
                         WHERE people.name ILIKE '%' || _pattern || '%') = 1
UNION ALL
SELECT 'No matching name'
       WHERE (SELECT count(*)
                     FROM people
                     WHERE people.name ILIKE '%' || _pattern || '%') = 0
UNION ALL
SELECT 'Non-distinct actor name'
       WHERE (SELECT count(*)
                     FROM people
                     WHERE people.name ILIKE '%' || _pattern || '%') > 1;
$$ 
LANGUAGE sql;

db<>fiddle