MYSQL SUBSTRING_INDEX提取列中的每個不同的字符串

我想要在MYSQL中的分隔符之間得到每個不同的字符串值。我嘗試使用函數SUBSTRING_INDEX，它適用於第一個字符串和第一個字符串的延續，但不是第二個字符串。這裏就是我的意思：MYSQL SUBSTRING_INDEX提取列中的每個不同的字符串

Table x     The result

SELECT SUBSTRING_INDEX(path, ':', 2) as p, sum(count) as N From x Group by p UNION 
SELECT SUBSTRING_INDEX(path, ':', 3) as p, sum(count) From x Group by p UNION 
SELECT SUBSTRING_INDEX(path, ':', 4) as p, sum(count) From x Group by p UNION 
SELECT SUBSTRING_INDEX(path, ':', 5) as p, sum(count) From x Group by p UNION 
SELECT SUBSTRING_INDEX(path, ':', 6) as p, sum(count) From x Group by p;

我試着在查詢中加入SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(path, ':', 2), ':', 2) as p, sum(count) From x Group by p UNION SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(path, ':', 4), ':', 2) as p, sum(count) From x Group by p，但結果還是一樣。我所試圖做的就是不僅字符串的結果A1，A2，A3的組合，而且還串B2，C2，D2爲第一串取像見下表：

+---------------+----+ 
| p   | N | 
+---------------+----+ 
| :A1   | 4 | 
| ...   | ...| 
| :B1   | 3 | 
| :B1:C2  | 2 | 
|...   | ...| 
+---------------+----+

什麼是正確的函數來得到這樣的結果？任何幫助表示讚賞，謝謝。

來源

2016-01-03 Jess Moi

[SQL拆分值到多行（的可能的複製http://stackoverflow.com/questions/17942508/sql-split-values-to-multiple-行） –

沒有路徑開始於：B1，你能否澄清這個輸出 – amdixon

@RyanVincent會檢查它。 –

假設路徑上所有的字符串節點是兩個字符長和所有路徑具有相同的長度..

計劃

從某些開始創建有效子的序列與端對每個塊使用固定長度爲2的路徑。

將以上連接到自身以獲取不走到路徑末端的路徑

使用上述方法計算的子串的索引取串上x.path

聚集求和上述x.path子序列

設置

create table x 
(
    path varchar(23) primary key not null, 
    count integer not null 
); 

insert into x 
(path, count) 
values 
(':A1:B2:C1:D1:G1' , 3), 
(':A1:B2:C1:D1:G4' , 1), 
(':A2:B1:C2:D2:G4' , 2) 
; 

drop view if exists digits_v; 
create view digits_v 
as 
select 0 as n 
union all 
select 1 union all select 2 union all select 3 union all 
select 4 union all select 5 union all select 6 union all 
select 7 union all select 8 union all select 9 
;

查詢

select substring(x.path, `start`, `len`) as chunk, sum(x.count) 
from x 
cross join 
(
    select o1.`start`, o2.`len` 
    from 
    (
    select 1 + 3 * seq.n as `start`, 15 - 3 * seq.n as `len` 
    from digits_v seq 
    where 1 + 3 * seq.n between 1 and 15 
    and 15 - 3 * seq.n between 1 and 15 
) o1 
    inner join 
    (
    select 1 + 3 * seq.n as `start`, 15 - 3 * seq.n as `len` 
    from digits_v seq 
    where 1 + 3 * seq.n between 1 and 15 
    and 15 - 3 * seq.n between 1 and 15 
) o2 
    on o2.`start` >= o1.`start` 
) splices 
where substring(x.path, `start`, `len`) <> '' 
group by substring(x.path, `start`, `len`) 
order by length(substring(x.path, `start`, `len`)), substring(x.path, `start`, `len`) 
;

輸出

+-----------------+--------------+ 
|  chunk  | sum(x.count) | 
+-----------------+--------------+ 
| :A1    |   4 | 
| :A2    |   3 | 
| :A3    |   3 | 
| ...    |   ... | 
| :A1:B2   |   4 | 
| :A2:B1   |   3 | 
| :A3:B3   |   2 | 
| :A3:B4   |   1 | 
| ...    |   ... | 
| :A1:B2:C1  |   4 | 
| :A2:B1:C2  |   2 | 
| :A2:B1:D2  |   3 | 
| :A3:B3:C4  |   2 | 
| :A3:B4:C2  |   1 | 
| ...    |   ... | 
| :A1:B2:C1:D1 |   4 | 
| :A2:B1:C2:D2 |   2 | 
| :A3:B3:C4:D3 |   2 | 
| :A3:B4:C2:D3 |   1 | 
| ...    |   ... | 
| :A1:B2:C1:D1:G1 |   3 | 
| :A1:B2:C1:D1:G4 |   1 | 
| :A2:B1:C2:D2:G4 |   2 | 
| :A3:B3:C4:D3:G7 |   2 | 
| :A3:B4:C2:D3:G7 |   1 | 
+-----------------+--------------+

sqlfiddle

來源

2016-01-03 16:33:09 amdixon

是的，輸出正是我所需要的。非常感謝！我會學習你的問題來理解這些功能。 –

主要是瞭解序列生成器和有效子串（來自固定長度的2個節點）。如果節點長度變長，則複雜度將進一步增加;） – amdixon

MYSQL SUBSTRING_INDEX提取列中的每個不同的字符串

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