从表中删除重复的行 [英] Deleting duplicate rows from a table
问题描述
id action
L1_name L1_data
L2_name L2_data
L3_name L3_data
L4_name L4_data
L5_name L5_data
L6_name L6_data
L7_name L7_data
L8_name L8_data
L9_name L9_data
L10_name L10_data
L11_name L11_data
L12_name L12_data
L13_name L13_data
L14_name L14_data
L15_name L15_data
看到这些都是我的字段:_
id对于每一行都是唯一的。
L11_data对于相应的操作字段是唯一的。
L11_data在
所以在我的数据中,我在L11_data中的公司的重复名称为他们各自的行业。
我想要的是在特定行业的公司的独特名称和其他数据存储在行动中。我希望我以一种你能够理解的方式表达我的问题。
是的,假设你有一个唯一的ID字段,您可以删除除ID之外的所有记录,但对于它们的值组不具有最小ID。
示例查询:
DELETE FROM Table
WHERE ID $ IN
(
SELECT MIN(ID)
FROM Table
GROUP BY Field1,Field2,Field3,...
)
注意:
- 我自由选择表和ID作为代表名称
- 字段列表(Field1,Field2,...)应包括ID除外的所有字段
- 这可能是一个缓慢的查询,取决于字段和行的数量,但是我期望与替代方案相比会更好。
编辑:如果没有唯一的索引,我的建议是简单地添加自动增量唯一索引。主要是因为它的设计很好,也是因为它可以让你运行上面的查询。
I have a table in my database which has duplicate records that I want to delete. I don't want to create a new table with distinct entries for this. What I want is to delete duplicate entries from the existing table without the creation of any new table. Is there any way to do this?
id action
L1_name L1_data
L2_name L2_data
L3_name L3_data
L4_name L4_data
L5_name L5_data
L6_name L6_data
L7_name L7_data
L8_name L8_data
L9_name L9_data
L10_name L10_data
L11_name L11_data
L12_name L12_data
L13_name L13_data
L14_name L14_data
L15_name L15_data
see these all are my fields :
id is unique for every row.
L11_data is unique for respective action field.
L11_data is having company names while action is having name of the industries.
So in my data I'm having duplicate name of the companies in L11_data for their respective industries.
What I want is to have is unique name and other data of the companies in the particular industry stored in action. I hope I have stated my problem in a way that you people can understand it.
Yes, assuming you have a unique ID field, you can delete all records that are the same except for the ID, but don't have "the minimum ID" for their group of values.
Example query:
DELETE FROM Table
WHERE ID NOT IN
(
SELECT MIN(ID)
FROM Table
GROUP BY Field1, Field2, Field3, ...
)
Notes:
- I freely chose "Table" and "ID" as representative names
- The list of fields ("Field1, Field2, ...") should include all fields except for the ID
- This may be a slow query depending on the number of fields and rows, however I expect it would be okay compared to alternatives
EDIT: In case you don't have a unique index, my recommendation is to simply add an auto-incremental unique index. Mainly because it's good design, but also because it will allow you to run the query above.
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