如何利用SQL查询返回庞大的整数序列表

dn001 2009-06-04 00:23:11

WITH Digits AS (
SELECT 0 as Number
UNION SELECT 1
UNION SELECT 2
UNION SELECT 3
UNION SELECT 4
UNION SELECT 5
UNION SELECT 6
UNION SELECT 7
UNION SELECT 8
UNION SELECT 9
)
SELECT
(d5.Number * 100000)
+ (d4.Number * 10000)
+ (d3.Number * 1000)
+ (d2.Number * 100)
+ (d1.Number * 10)
+ d0.Number as Number
FROM
Digits AS d0
, Digits AS d1
, Digits AS d2
, Digits AS d3
, Digits AS d4
, Digits AS d5
在SQLServer 2005中,这个SQL返回一个包含1000000条记录的结果集,从0到999999。
这条语句利用了SQL2005的新功能：CTE (Common Table Expression)
如果当前的数据库是SQL 2000或其他不支持CTE的数据库，则可以将WITH部分的SQL定义为一个视图。

CREATE VIEW .[Digits] AS
SELECT 0 AS Number
UNION SELECT 1
UNION SELECT 2
UNION SELECT 3
UNION SELECT 4
UNION SELECT 5
UNION SELECT 6
UNION SELECT 7
UNION SELECT 8
UNION SELECT 9;

CREATE VIEW [MillionNumbers] AS
SELECT
SELECT (d5.Number * 100000)
+ (d4.Number * 10000)
+ (d3.Number * 1000)
+ (d2.Number * 100)
+ (d1.Number * 10)
+ d0.Number) as Number
FROM
Digits AS d0
, Digits AS d1
, Digits AS d2
, Digits AS d3
, Digits AS d4
, Digits AS d5;

我们可以用这个方法来生成大批量的测试数据。如：
INSERT INTO MyTest (RecordId, RecordIndex)
SELECT newid(), Number FROM MillionNumbers

用此方法插入数据，要比利用循环快很多倍。