Updating row selected by cursor

The sub-query can refer to old values of the current row of the table being updated.you should ensure that the join produces at most one output row for each row to be modified.That allows us to perform operations on every record on a one-by-one basis.

This compatibility table still uses the old format, because we haven't yet converted the data it contains. In an assignment phrase, column names are on the left and the values or expressions containing the assignment values are on the right. A column name can be used in expressions on the right.The old value of the column will always be used in these right-side values, even if the column was already assigned a new value earlier in the It was not always like that.The sub-query must yield no more than one row when executed.If it yields one row, its column values are assigned to the target columns; if it yields no rows, NULL values are assigned to the target columns.

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