Sql updating multiple columns can carbon dating
My SQL UPDATE using NULL My SQL UPDATE command can be used to update a column value to NULL by setting column_name = NULL, where column_name is the name of the column to be updated.
But we can group the updates according to the value being set, and then do one UPDATE statement per distinct value.
But if there are a large number of rows that require an update, then the overhead of issuing large numbers of UPDATE statements can result in the operation as a whole taking a long time to complete.
The traditional advice for improving performance for multiple UPDATE statements is to “prepare” the required query once, and then “execute” the prepared query once for each row requiring an update.
A requirement arises in many systems to update multiple SQL database rows.
For small numbers of rows requiring updates, it can be adequate to use an UPDATE statement for each row that requires an update.