如何在PostgreSQL中引發通知？

Question

我想在PostgreSQL的9.2運行此：

RAISE NOTICE 'hello, world!'; 

而且服務器說：

Error : ERROR: syntax error at or near "RAISE" 
LINE 1: RAISE NOTICE 'hello, world!' 
     ^

爲什麼？

Answer 1

使用匿名code block：

DO language plpgsql $$ 
BEGIN 
    RAISE NOTICE 'hello, world!'; 
END 
$$; 

Variables are referenced使用%：

RAISE NOTICE '%', variable_name; 

Answer 2

raise僅限於PL/pgSQL。

http://www.postgresql.org/docs/current/static/plpgsql-errors-and-messages.html

create or replace function r(error_message text) returns void as $$ 
begin 
    raise notice '%', error_message; 
end; 
$$ language plpgsql; 

select r('an error message'); 
NOTICE: an error message 

Answer 3

簡單的例子：

CREATE OR REPLACE FUNCTION test()  
RETURNS TRIGGER AS 
' 
DECLARE 


num int; 

BEGIN 
IF TG_OP = ''INSERT'' THEN 
select count(*) into num from test_table; 
IF num >= 1 THEN 
RAISE WARNING ''Cannot Insert more than one row''; 
RETURN OLD; 
END IF; 
ELSE 
RETURN NEW; 
END IF; 

END; 
' LANGUAGE plpgsql;