| 摘要 |
Database management systems allow modification of existing table rows through update statements or other data modification commands. For example, a user may specify, via a command statement, the table to update, the columns to modify and their respective new value(s), and qualify the rows to be updated. Optimized constraint and index maintenance for data modification statements and commands is provided where the new value being assigned to the columns is actually the same as the current value, e.g., update commands that actually leave the columns unchanged.
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