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What happens when a new value for an existing column is added? Will the older value be overwritten by the new value? Or the older value will also retain and can be retrieved (similar to simpleDB)?
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The UPDATE statement in SQL is used to update the data of an existing table in database. We can update single columns as well as multiple columns using UPDATE statement as per our requirement. UPDATE table_name SET column1 = value1, column2 = value2,...
We have to use the SET keyword in the UPDATE command for modifying the value of the columns. WHERE clause specifies which row you want to change.
The UPDATE command in SQL is used to modify or change the existing records in a table. If we want to update a particular value, we use the WHERE clause along with the UPDATE clause. If you do not use the WHERE clause, all the rows will be affected.
The older value is overwritten (technically, hidden by the new and eventually garbage collected).
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