How does the UPDATE statement retain the previous data? -Php Tutorial

Source: Internet
Author: User
How does the UPDATE statement retain the previous data? When updating field A, you want to keep the original data instead of overwriting it all.
It's text content. I don't want to read it first. it's the write method. How can I write an UPDATE statement?

Reply to discussion (solution)

Please give an example!

Please give an example!

For example, the content of field a is abc.

UPDATE 'user' SET 'a' = 'AAA' WHERE 'id' = '10 ';

After Execution, the content of field a is aaa. the updated data is acbaaa.

UPDATE 'user' SET 'a' = concat ('A', 'AAA') WHERE 'id' = '10 ';

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