SQL 查詢欄位重複值筆數：GROUP BY + HAVING 一行搞定

核心語法

-- 查出重複 id 及其出現次數
SELECT id, COUNT(id) 
FROM @table 
GROUP BY id 
HAVING COUNT(id) > 1;

邏輯拆解

1. GROUP BY id：依 id 分組
2. COUNT(id)：統計各組筆數
3. HAVING COUNT(id) > 1：過濾保留重複組

延伸：查看所有 id 分布

SELECT id, COUNT(id) 
FROM @table 
GROUP BY id;