将INSERT INTO转换为UPDATE [复制]

Question

This question already has an answer here:

• Update a column in MySQL 5 answers

Imagine I have some code like this:

$sql = "INSERT INTO tablename (column1, column2, column3) VALUES 
('1','2','3')"; 

How would I convert this into an UPDATE query? I did some searching, but

UPDATE table_name 
SET column1=value1,column2=value2,... 
WHERE some_column=some_value;

doesn't make much sense to me. Thanks

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Answer 1

INSERT and UPDATE queries look similar but they do different things.

Inserts => Inserts new nonexisting data into table

Update => Updates existing data inside of the table

That is why the UPDATE query has WHERE clause

So, you can use UPDATE to modify a row which is already inserted.