![](/img/trans.png)
[英]How to select a single row from an sql table with multiple rows having same value in a column
[英]How can I select rows in an SQL table by using multiple substrings of a single column value?
我正在使用 Oracle SQL Developer 查詢案例數據庫,我需要使用三個不同的標識符為每個案例選擇正確的行; 但是,我的問題是兩個標識符包含在同一個文本字符串中,我不知道如何解析它們以在查詢中使用。
在下表中,我需要使用的標識符是:
案件 | 序列 | 值 1 | 值 2 |
---|---|---|---|
AA1001 | 672 | 73 | 195 |
AA1001 | 711 | 73 | 185 |
AA1001-01 | 680 | 73 | 185 |
AA1001-02 | 685 | 72 | 185 |
AA1001-02 | 699 | 72 | 182 |
AB1002 | 676 | 51 | 36 |
AB1002-01 | 701 | 48 | 39 |
AB1002-01 | 719 | 48 | 35 |
AB1002-02 | 707 | 51 | 38 |
AA1003 | 655 | 122 | 416 |
AA1003 | 683 | 113 | 416 |
我想為每個唯一的 ID-1 返回一行,這樣首先選擇 ID-2 的最大值,然后選擇該子集中ID-3 的最大值; 因此,查詢應僅返回上表中的以下三行。
案件 | 序列 | 值 1 | 值 2 |
---|---|---|---|
AA1001-02 | 699 | 72 | 182 |
AB1002-02 | 707 | 51 | 38 |
AA1003 | 683 | 113 | 416 |
我嘗試使用以下方法為 ID-2 取最大值,但它只返回 ID-2 等於“02”的行。
SELECT *
FROM table
WHERE SUBSTR(Case,3,4) in ('1001','1002','1003')
and SUBSTR(Case,8,2) = (SELECT MAX(SUBSTR(Case,8,2))
FROM table
WHERE SUBSTR(Case,3,4) in ('1001','1002','1003'))
(最簡單的答案可能只是為 ID-2 添加一列;但是,源數據庫是嚴格只讀的,因此我無法進行此類更改。)
在 Oracle 12.1 及更高版本中,您可以使用match_recognize
子句:
select case, sequence, value1, value2
from (
select t.*, substr(case, 3, 4) as id_1, substr(case, 8, 9) as id_2
from table_name t
)
match_recognize(
partition by id_1
order by id_2 desc nulls last, sequence desc nulls last
all rows per match
pattern (^ x)
define x as null is null
);
CASE SEQUENCE VALUE1 VALUE2
--------- ---------- ---------- ----------
AA1001-02 699 72 182
AB1002-02 707 51 38
AA1003 683 113 416
您可以使用ROW_NUMBER()
分析函數並通過以下方式找到要分區/排序的SUBSTR
ings:
SELECT *
FROM (
SELECT t.*,
ROW_NUMBER() OVER (
PARTITION BY
SUBSTR(Case, 3, 4)
ORDER BY
COALESCE(SUBSTR(Case, 8, 2), '00') DESC,
Sequence DESC
) AS rn
FROM table_name t
)
WHERE rn = 1;
其中,對於您的示例數據:
CREATE TABLE table_name (Case, Sequence, Value1, Value2 ) AS
SELECT 'AA1001', 672, 73, 195 FROM DUAL UNION ALL
SELECT 'AA1001', 711, 73, 185 FROM DUAL UNION ALL
SELECT 'AA1001-01', 680, 73, 185 FROM DUAL UNION ALL
SELECT 'AA1001-02', 685, 72, 185 FROM DUAL UNION ALL
SELECT 'AA1001-02', 699, 72, 182 FROM DUAL UNION ALL
SELECT 'AB1002', 676, 51, 36 FROM DUAL UNION ALL
SELECT 'AB1002-01', 701, 48, 39 FROM DUAL UNION ALL
SELECT 'AB1002-01', 719, 48, 35 FROM DUAL UNION ALL
SELECT 'AB1002-02', 707, 51, 38 FROM DUAL UNION ALL
SELECT 'AA1003', 655, 122, 416 FROM DUAL UNION ALL
SELECT 'AA1003', 683, 113, 416 FROM DUAL;
輸出:
案件 序列 VALUE1 VALUE2 注冊護士 AA1001-02 699 72 182 1 AB1002-02 707 51 38 1 AA1003 683 113 416 1
db<> 在這里擺弄
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.