Data modification statements, such as INSERT, UPDATE, and DELETE combine both modification and read operations. The statement first performs read operations to acquire data before performing the required modification operations. Data modification statements, therefore, typically request both shared locks and exclusive locks. For example, an UPDATE statement might modify rows in one table based on a join with another table. In this case, the UPDATE statement requests shared locks on the rows read in the join table in addition to requesting exclusive locks on the updated rows.
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