请问如何在postgre下声明一个变量

[幕落希望之城]

请问如何在postgre下声明一个变量 ？我在SQL中定义如下，现在转化成为postgre,总是有问题，不知道如何解决。
declare @A datetime
declare @B decimal(13,5)
declare @X decimal(13,5)
declare @Y decimal(13,5)

set @A=(select top 1 N_A from task1 where n_id=1 order by N_date desc)
set @B=(select top 1 N_B from task1 where n_id=1 order by N_date desc)

while right(convert(varchar(19),@A,120),8) between '00:00:00'and'03:00:00'
begin
set @X=round(RAND()*10,0)
set @Y=round(RAND()*10,0)
set @A=dateadd(mi,15,@A)
set @B=@B+@X

INSERT INTO task1(N_date,n_id,ACQ_9010)
VALUES(@A,1,@B)

end


现在我在声明变量中遇到了问题，
我将@A的声明变量改成这样，但是总是报错，不知道是为什么？

DECLARE

n_date timestamp :=(select top 1 N_A from task1 where n_id=1 order by N_date desc);
end

[幕落希望之城]

[Quote=引用 8 楼 acmain_chm 的回复:]
引用可是在运行的时候还是会报错
ERROR: unterminated dollar-quoted string at or near "$$
DECLARE n_date timestamp;
n_date timestamp :=(select N_A from task1 where n_id=1 order by N_date desc limit 1);

你的完整语句是什么？……
[/Quote]

谢谢了，我已经弄出来了，postgre的语句和SQL server的区别不小

[ACMAIN_CHM]

错误信息是什么？

参考一下手册中的例子

[Quote]CREATE OR REPLACE FUNCTION getAllFoo() RETURNS SETOF foo AS
$BODY$
DECLARE
r foo%rowtype;
BEGIN
FOR r IN SELECT * FROM foo
WHERE fooid > 0
LOOP
-- can do some processing here
RETURN NEXT r; -- return current row of SELECT
END LOOP;
RETURN;
END
$BODY$
LANGUAGE 'plpgsql' ;

[/Quote]

[WWWWA]

CREATE FUNCTION dt1() RETURNS SETOF record AS $$
DECLARE n_date timestamp;
n_date timestamp :=(select N_A from task1 where n_id=1 order by N_date desc limit 1);

[幕落希望之城]

[Quote=引用 1 楼 acmain_chm 的回复:]

错误信息是什么？

参考一下手册中的例子

引用CREATE OR REPLACE FUNCTION getAllFoo() RETURNS SETOF foo AS
$BODY$
DECLARE
r foo%rowtype;
BEGIN
FOR r IN SELECT * FROM foo
WHERE fooid > 0
LOOP
……
[/Quote]

错误信息是 ：
ERROR: syntax error at or near "timestamp"
LINE 26: n_date timestamp :=(select top 1 N_A from task1 where n_id...
^

********** 错误 **********

ERROR: syntax error at or near "timestamp"
SQL 状态: 42601
字符:1220

[幕落希望之城]

[Quote=引用 2 楼 wwwwa 的回复:]

CREATE FUNCTION dt1() RETURNS SETOF record AS $$
DECLARE n_date timestamp;
n_date timestamp :=(select N_A from task1 where n_id=1 order by N_date desc limit 1);
[/Quote]
可以问一下$$这个是用来做什么的？

[ACMAIN_CHM]

[Quote]可以问一下$$这个是用来做什么的？[/Quote]语法分隔符。

[幕落希望之城]

[Quote=引用 5 楼 acmain_chm 的回复:]
引用可以问一下$$这个是用来做什么的？语法分隔符。
[/Quote]

可是在运行的时候还是会报错
ERROR: unterminated dollar-quoted string at or near "$$
DECLARE n_date timestamp;
n_date timestamp :=(select N_A from task1 where n_id=1 order by N_date desc limit 1);

"
LINE 4: CREATE FUNCTION dt1() RETURNS SETOF record AS $$
^

********** 错误 **********

ERROR: unterminated dollar-quoted string at or near "$$
DECLARE n_date timestamp;
n_date timestamp :=(select N_A from task1 where n_id=1 order by N_date desc limit 1);

"
SQL 状态: 42601
字符:50

[WWWWA]

ZW=# CREATE FUNCTION dtA() RETURNS SETOF record AS $$
ZW$# DECLARE n_date timestamp :=(select N_A from task1 where n_id=1 order by N_d
ate desc limit 1);
ZW$# BEGIN
ZW$# END;
ZW$#  $$ LANGUAGE plpgsql;
CREATE FUNCTION
ZW=#

[ACMAIN_CHM]

[Quote]可是在运行的时候还是会报错
ERROR: unterminated dollar-quoted string at or near "$$
DECLARE n_date timestamp;
n_date timestamp :=(select N_A from task1 where n_id=1 order by N_date desc limit 1);[/Quote]

你的完整语句是什么？