技術標籤：SQLsql去重資料庫去重

book表中的資料：

根據所有欄位去重：

SELECT DISTINCT * from dbo.book 

sql根據多個欄位去重：

SELECT title,isbn,author_id ,page_count  from dbo.book 
group by title,isbn,author_id ,page_count
 

或者：
SELECT DISTINCT title,isbn,author_id ,page_count from dbo.book

sql根據多個欄位去重,並且返回所有欄位：

SELECT * from dbo.book a where id in (SELECT max(id) from dbo.book 
group by title,isbn,author_id ,page_count )
 

如果資料量比較大的話in會有效率問題，可以採用以下寫法

SELECT a.* from dbo.book a , (SELECT max(id) as id from dbo.book 
group by title,isbn,author_id ,page_count )b where a.id = b.id

有問題歡迎指正