An SQL UPDATE statement changes the data of one or more records in a table. Either all the rows can be updated, or a subset may be chosen using a condition.
The UPDATE statement has the following form:
UPDATE table_name SET column_name = value [, column_name = value ...] [WHERE condition]
For the UPDATE to be successful, the user must have data manipulation privileges (UPDATE privilege) on the table or column, the updated value must not conflict with all the applicable constraints (such as primary keys, unique indexes, CHECK constraints, and NOT NULL constraints).