在同一表中的一列上查找不同值的 SQL 查詢

Question

but a few days ago I realized that I need larger scope which was extended and proper value should be .我有下表，其中Description字段的scope = 10並且我插入了第一行Description = 但幾天前我意識到我需要更大的范圍，並且適當的值應該是 。

Column_ref     Description     Date          Money     Doc_nr
123            Cobra - Ni      06-11-2015    505.50    2000/10
123            Cobra - Toung   07-11-2015    505.50    2000/12
123            Cobra - Brain   07-11-2015    505.50    2000/25
123            Cobra - Nisyor  07-11-2015    505.50    2000/10

我需要編寫從這個示例表中找到第一行和最后一行的查詢。

我這樣試過：

SELECT t1.*
FROM table as t1
WHERE t1.Description in
      (SELECT t2.Description
       FROM table as t2
       WHERE t1.Doc_nr = t2.Doc_nr
       AND t1.Description != t2.Description)

但它不起作用。

Answer 1

我假設“范圍”是指列的寬度為 10。因此，您希望關聯行，其中一個長度為 10，另一個以相同的字符串開頭且長度 > 10。我們可以使用LEN()函數獲取字符字段的長度， LEFT()獲取子字符串 - 后者我們可以用來比較“新”和“舊”。

例如：

with oldRows as (
    select *
    from myTable
    where LEN(Description) = 10
), newRows as (
    select *, LEFT(Description, 10) as oldKey
    from myTable
    where LEN(Description) > 10
)
select n.*, o.*
from oldRows o
join newRows n on o.Description = n.oldKey
-- Of course add any other comparisons you need to correlate rows:
--    and o.Column_ref = n.Column_ref
--    and o.[Date] = n.[Date]
--    and o.[Money] = n.[Money]
--    and o.Doc_nr = n.Doc_nr

為了將來參考，您可能不應該在意識到問題后在表中插入額外的新行，而應該使用更新。

Answer 2

要查找您要查找的行，您需要對doc_nr進行自doc_nr僅包括那些描述不匹配的行， SQL Fiddle 。

CREATE TABLE basic
(
  column_ref INT,
  description VARCHAR(30),
  dateField DATETIME,
  amount DECIMAL(12,2),
  doc_nr VARCHAR(30)
);

INSERT INTO basic (column_ref, description, dateField, amount, doc_nr)
VALUES (123, 'Cobra - Ni', '06/11/2015',505.50,'2000/10'),
       (123, 'Cobra - Toung', '07/11/2015',505.50,'2000/12'),
       (123, 'Cobra - Brain', '07/11/2015',505.50,'2000/25'),
       (123, 'Cobra - Nisyor', '07/11/2015',505.50,'2000/10');

SELECT *
FROM basic b
JOIN basic q ON b.doc_nr = q.doc_nr
WHERE b.description != q.description

╔════════════╦════════════════╦════════════════════════╦════════╦═════════╦════════════╦════════════════╦════════════════════════╦════════╦═════════╗
║ column_ref ║  description   ║       dateField        ║ amount ║ doc_nr  ║ column_ref ║  description   ║       dateField        ║ amount ║ doc_nr  ║
╠════════════╬════════════════╬════════════════════════╬════════╬═════════╬════════════╬════════════════╬════════════════════════╬════════╬═════════╣
║        123 ║ Cobra - Ni     ║ June, 11 2015 00:00:00 ║ 505.5  ║ 2000/10 ║        123 ║ Cobra - Nisyor ║ July, 11 2015 00:00:00 ║ 505.5  ║ 2000/10 ║
║        123 ║ Cobra - Nisyor ║ July, 11 2015 00:00:00 ║ 505.5  ║ 2000/10 ║        123 ║ Cobra - Ni     ║ June, 11 2015 00:00:00 ║ 505.5  ║ 2000/10 ║
╚════════════╩════════════════╩════════════════════════╩════════╩═════════╩════════════╩════════════════╩════════════════════════╩════════╩═════════╝

為了實際DELETE行，請將上面的SELECT語句替換為以下內容（如果您要DELETE描述較短的行，您的實際條件可能會有所不同）。

DELETE b 
FROM basic b
JOIN basic q ON b.doc_nr = q.doc_nr
WHERE LEN(b.description) < LEN(q.description);

歸功於此處的上述語法。