在 MS SQL Server 中查找重复项

原文:https://www . geesforgeks . org/find-duplicates-in-ms-SQL-server/

我们可以使用以下方法来查找表中的重复值。

  • 分组依据条款。
  • ROW_NUMBER()函数。

1。使用 GROUP BY 子句查找重复值:

语法:

SELECT col1, col2, ...COUNT(*)
FROM table_name
GROUP BY col1, col2, ...
HAVING COUNT(*) > 1;

示例– 让我们创建一个名为 Geek 的表，该表包含三列 ID、A 和 b

CREATE TABLE Geek (
ID INT IDENTITY(1, 1),
A INT,
B INT,
PRIMARY KEY(id));

让我们给 Geek 表增加一些值–

INSERT INTO Geek (A, B)
VALUES (1, 1),(1, 2), (1, 3), (2, 1),
(1, 2), (1, 3), (2, 1), (2, 2);

我们知道 Geek 表包含以下重复行–

(1, 2) (2, 1) (1, 3)

使用极客表中的分组依据子句查找重复行的微软 SQL Server 查询:

SELECT A, B, COUNT(*) AS num
FROM Geek
GROUP BY A, B
HAVING COUNT(*) > 1;

输出–

表–极客

A B 数字
Two one Two
one Two Two
one three Two

要查找每个重复行的完整行详细信息，请使用 CTE 将上述查询的输出与 Geek 表连接起来:

WITH CTE AS ( 
SELECT A, B, COUNT(*) AS num
FROM Geek
GROUP BY A, B
HAVING COUNT(*) > 1
)
SELECT Geek.ID, Geek.A, Geek.B
FROM Geek
INNER JOIN CTE ON
CTE.A = Geek.A AND CTE.B = Geek.B
ORDER BY Geek.A, Geek.B;

输出–

表–极客

身份证明 A B
Two one Two
five one Two
six one three
three one three
four Two one
seven Two one

2。使用 ROW_NUMBER()函数查找重复值:

语法:

WITH cte AS (
SELECT col,ROW_NUMBER() OVER (
PARTITION BY col
ORDER BY col) AS row_num
FROM table_name
)  
SELECT * 
FROM cte  
WHERE row_num > 1;

使用极客表中的 ROW_NUMBER()函数查找重复行的 MS SQL Server 查询:

WITH CTE AS (
SELECT A, B,
ROW_NUMBER() OVER (
PARTITION BY A, B
ORDER BY A, B
) AS rownum
FROM Geek
)
SELECT *
FROM CTE
WHERE rownum > 1;

输出–

表–极客

A B 行
one Two Two
one three Two
Two one Two

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