我有几个加入了CTE。比如:
;With CT1 AS(SELECT ..)
, CT2 AS(select)
SELECT *.T1,*T2 FROM CT1 T1 INNER JOIN CT2 T2 WHERE (some Condition ) GROUP BY (F1,F2, etc)
现在我需要将这个查询的结果连接到另一个CTE。最好的方法是什么?我可否凭此查询的结果制作综合电子考试证书?任何帮助都将非常感激。
您可以根据先前定义的cte继续创建新的cte。它们可以联合或以其他方式组合,但须遵守cte的规则。
; with
ArabicRomanConversions as (
select *
from ( values
( 0, '', '', '', '' ), ( 1, 'I', 'X', 'C', 'M' ), ( 2, 'II', 'XX', 'CC', 'MM' ), ( 3, 'III', 'XXX', 'CCC', 'MMM' ), ( 4, 'IV', 'XL', 'CD', '?' ),
( 5, 'V', 'L', 'D', '?' ), ( 6, 'VI', 'LX', 'DC', '?' ), ( 7, 'VII', 'LXX', 'DCC', '?' ), ( 8, 'VIII', 'LXXX', 'DCCC', '?' ), ( 9, 'IX', 'XC', 'CM', '?' )
) as Placeholder ( Arabic, Ones, Tens, Hundreds, Thousands )
),
Numbers as (
select 1 as Number
union all
select Number + 1
from Numbers
where Number < 3999 ),
ArabicAndRoman as (
select Number as Arabic,
( select Thousands from ArabicRomanConversions where Arabic = Number / 1000 ) +
( select Hundreds from ArabicRomanConversions where Arabic = Number / 100 % 10 ) +
( select Tens from ArabicRomanConversions where Arabic = Number / 10 % 10 ) +
( select Ones from ArabicRomanConversions where Arabic = Number % 10 ) as Roman
from Numbers ),
Squares as (
select L.Arabic, L.Roman, R.Arabic as Square, R.Roman as RomanSquare
from ArabicAndRoman as L inner join
ArabicAndRoman as R on R.Arabic = L.Arabic * L.Arabic
where L.Arabic < 16 ),
Cubes as (
select S.Arabic, S.Roman, S.Square, S.RomanSquare, A.Arabic as Cube, A.Roman as RomanCube
from Squares as S inner join
ArabicAndRoman as A on A.Arabic = S.Square * S.Arabic )
select *
from Cubes
order by Arabic
option ( MaxRecursion 3998 )
这是我使用过几次的格式,其中使用临时表来缓冲一个复杂的CTE,该CTE是输出的,然后再次从临时表中使用第二个CTE。
如果您需要2个结果集,或者如果完整的CTE作为一个大语句导致速度问题(在某些情况下,分解它可以极大地提高性能),
-- I do this "DROP" because in some cases where query is executed over and
-- over sometimes the object is not cleared before next transaction.
BEGIN TRY DROP TABLE #T_A END TRY BEGIN CATCH END CATCH;
WITH A AS (
SELECT 'A' AS Name, 1 as Value
UNION ALL SELECT 'B', 2
)
SELECT *
INTO #T_A
FROM A;
SELECT *
FROM #T_A ; -- Generate First Output Table
WITH B AS (
SELECT 'A' AS Name, 234 as Other
UNION ALL SELECT 'B', 456
)
-- Generate second result set from Temp table.
SELECT B.*, A. Value
FROM B JOIN #T_A AS A ON A.Name=B.Name
生成一个2表的结果集。