對了單排兩排

Question

我有這個表：由於考慮到Type 1第一記錄必須以匹配

A B   C 
1 Record 1 Type 1 
2 Record 2 Type 2 
3 Record 3 Type 1 
4 Record 4 Type 2 

我需要他們的價值觀在C來配對行（類型1 &類型2）最近ID與Type 2

所需的輸出：

A B   C  A B   C 
1 Record 1 Type 1 2 Record 2 Type 2 
3 Record 3 Type 1 4 Record 4 Type 2 

我試着做次在與2個CTE的查詢，但我不能想出了預期的結果：

WITH SET_A (A, B, C) AS 

    (SELECT * FROM A WHERE C = 'Type 1'), 

SET_B (A, B, C) AS 
    (SELECT * FROM A WHERE C = 'Type 2') 

SELECT * FROM SET_A CROSS JOIN SET_B; 

是否有任何其他的方法比使用交叉連接？

Answer 1

在這裏你去。對於每個「類型1」，它將找到最近的後續（按ID）「類型2」。

http://sqlfiddle.com/#!6/a5263/20

CREATE TABLE t 
(
    A int, 
    B varchar(32), 
    C varchar(32) 
); 



insert into t values (1, 'Record 1', 'Type 1') 
insert into t values (2, 'Record 2', 'Type 2') 
insert into t values (3, 'Record 3', 'Type 1') 
insert into t values (4, 'Record 4', 'Type 2') 
insert into t values (5, 'Record 5', 'Type 1') 
insert into t values (6, 'Record 6', 'Type 1a') 
insert into t values (7, 'Record 7', 'Type 2') 


; 

with set_a as 
(
    select * from t where c = 'type 1' 
) 
, set_b as 
(
    select a, b, c, a_match = (select max(t2.a) from t t2 where t2.a < t.a and t2.c = 'type 1') 
    from t where c = 'type 2' 
) 
select set_a.* , a2 = set_b.a, b2 = set_b.b, c2 = set_b.c 
from set_a 
join set_b on set_b.a_match = set_a.a 

Answer 2

試試這個

SELECT * FROM yourtable t1, yourtable t2 WHERE t1.c=t2.c 

Answer 3

SELECT t1.a a1, t1.b b1, t1.c c1, t2.a a2, t2.b b2, t2.c c2 
FROM Table1 t1 
JOIN Table1 t2 ON t1.c = 'Type 1' AND t2.c = 'Type 2' AND t1.a < t2.a 
WHERE t2.a = (SELECT MIN(t3.a) FROM Table1 t3 WHERE t3.c = 'Type 2' AND t3.a > t1.a) 

SQL Fiddle