[英]Function to select random Id
我想选择一个随机ID,我的列Guy_Checked
不是1。
这是我的代码:
CREATE FUNCTION dbo.get_rand_id()
RETURNS int
AS
BEGIN
DECLARE @ret int;
set @ret = (select top 1 Guy_ID
FROM SantaGuys
WHERE Guy_Checked <> 1
ORDER BY RAND())
RETURN @ret;
END;
SQL Server返回错误443,如...
"Invalid use of the "rand" operator, which has side effects, in a function."
我究竟做错了什么?
使用NEWID()
代替:
CREATE FUNCTION dbo.get_rand_id()
RETURNS int
AS
BEGIN
DECLARE @ret int;
SET @ret = (SELECT top 1 Guy_ID
FROM SantaGuys
WHERE Guy_Checked <> 1
ORDER BY NEWID()
)
RETURN @ret;
END;
在查询过程中, RAND()
实际上是一个常量 - 它在查询开始处理之前被评估一次。 NEWID()
每次调用时都会生成一个不同的id。
你可以使用newid()
检查它,它将创建uniqueidentifier类型的唯一值。
CREATE FUNCTION dbo.get_rand_id()
RETURNS int
AS
BEGIN
DECLARE @ret int;
set @ret = (select top 1 Guy_ID
FROM SantaGuys
WHERE Guy_Checked <> 1
ORDER BY NEWID())
RETURN @ret;
END;
我提供了这个答案,我从这篇文章中改编了......
-- Build the table
SELECT 123 as Guy_ID
,0 as Guy_Checked INTO SantaGuys;
INSERT INTO SantaGuys VALUES (234, 1);
INSERT INTO SantaGuys VALUES (456, 0);
INSERT INTO SantaGuys VALUES (567, 1);
GO
-- Create a view of RAND() to work around the Invalid use of side-effecting error
CREATE VIEW v_get_rand_id
AS
SELECT RAND() as rand_id;
GO
-- Build the function with parameters that will be in your SELECT query
CREATE FUNCTION dbo.get_rand_id(@my_Guy_ID as int, @my_Guy_Checked as int)
RETURNS float
AS
BEGIN
DECLARE @my_rand_id float;
SET @my_rand_id = (SELECT CASE WHEN @my_Guy_Checked <> 1
THEN v.rand_id
ELSE 0 END as my_rand_id
FROM v_get_rand_id v)
RETURN @my_rand_id;
END;
GO
-- Run your query and enjoy the results
SELECT sg.Guy_ID
,sg.Guy_Checked
,dbo.get_rand_id(sg.Guy_ID, sg.Guy_Checked) as my_rand_id
FROM SantaGuys sg;
这是一个结果......
+--------+-------------+-----------------+
| Guy_ID | Guy_Checked | my_rand_id |
+--------+-------------+-----------------+
| 123 | 0 | 0.5537264103585 |
| 234 | 1 | 0 |
| 456 | 0 | 0.227823559345 |
| 567 | 1 | 0 |
+--------+-------------+-----------------+
通过此链接轻松生成ASCII表。 希望这可以帮助
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