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When updating a table in MySQL, for example:
Table
user
user_id | user_name 1 John 2 Joseph 3 Juan If I run the query
UPDATE `user` SET user_name = 'John' WHERE user_id = 1 Will MySQL write the same value again or ignore it since it's the same content?
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If you tell SQL Server to UPDATE some rows - it will update those rows. SQL Server doesn't do any "matching" of its own. That's up to you - you control the WHERE clause for the UPDATE .
MySQL UPDATE multiple columnsMySQL UPDATE command can be used to update multiple columns by specifying a comma separated list of column_name = new_value. Where column_name is the name of the column to be updated and new_value is the new value with which the column will be updated.
For the single-table syntax, the UPDATE statement updates columns of existing rows in the named table with new values. The SET clause indicates which columns to modify and the values they should be given. Each value can be given as an expression, or the keyword DEFAULT to set a column explicitly to its default value.
We can update multiple columns by specifying multiple columns after the SET command in the UPDATE statement. The UPDATE statement is always followed by the SET command, it specifies the column where the update is required.
As the MySQL manual for the UPDATE statement implies,
If you set a column to the value it currently has, MySQL notices this and does not update it.
So, if you run this query, MySQL will understand that the value you're trying to apply is the same as the current one for the specified column, and it won't write anything to the database.
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