带有 case 语句的简单 Postgres UDF 不起作用

Question

当我运行以下代码时：

create or replace function roundfind(dates date) returns varchar as $$



begin 

select
case 
    when dates between '2020-06-08' and '2020-11-14' and dates is not null then return 'Round 1'
    when dates between '2020-11-15' and '2021-02-17' and dates is not null then return 'Round 2'
    when dates between '2021-02-18' and '2021-04-28' and dates is not null then return 'Round 3'
    when dates between '2021-04-29' and '2021-07-16' and dates is not null then return 'Round 4'
    when dates between '2021-07-16' and '2021-10-03' and dates is not null then return 'Round 5'
    when dates between '2021-10-04' and '2021-11-30' and dates is not null then return 'Round 6'
    when dates between '2021-12-01' and '2022-02-01' and dates is not null then return 'Round 7'
    when dates between '2021-02-02' and '2022-03-28' and dates is not null then return 'Round 8'
    when dates >= '2022-03-29' and dates is not null then return 'Round 9'
end 

end; $$

language PLPGSQL;


postgres.roundfind(date(19-5-2007)) -- function call

总会有一些错误，最近的错误是： “语言未定义”。虽然我已经定义清楚了。

Answer 1

如果使用PL/pgSQL，则需要使用RETURN QUERY SELECT ...

但是你不需要PL/pgSQL来封装一个简单的查询，使用language sql并去掉begin ... end

另外 then return 应该是 then

create or replace function roundfind(dates date) returns varchar 
as $$
select
case 
    when dates between '2020-06-08' and '2020-11-14' and dates is not null then 'Round 1'
    when dates between '2020-11-15' and '2021-02-17' and dates is not null then 'Round 2'
    when dates between '2021-02-18' and '2021-04-28' and dates is not null then 'Round 3'
    when dates between '2021-04-29' and '2021-07-16' and dates is not null then 'Round 4'
    when dates between '2021-07-16' and '2021-10-03' and dates is not null then 'Round 5'
    when dates between '2021-10-04' and '2021-11-30' and dates is not null then 'Round 6'
    when dates between '2021-12-01' and '2022-02-01' and dates is not null then 'Round 7'
    when dates between '2021-02-02' and '2022-03-28' and dates is not null then 'Round 8'
    when dates >= '2022-03-29' and dates is not null then 'Round 9'
end;
$$
language sql;

Online example

请注意，您的 CASE 表达式 中的 and dates is not null 条件是多余的，因为 between 仅 return true 如果值不为空。

带有 case 语句的简单 Postgres UDF 不起作用

simple Postgres UDF with case statement not working

postgresql

case

user-defined-functions