Update rows
Use the UPDATE statement to change the contents of one or more existing rows of a table, according to the specifications of the SET clause. This statement takes two fundamentally different forms. One lets you assign specific values to columns by name; the other lets you assign a list of values (that might be returned by a SELECT statement) to a list of columns. In either case, if you are updating rows, and some of the columns have data integrity constraints, the data that you change must conform to the constraints placed on those columns. For more information, refer to Data integrity.
Note: An alternative to the UPDATE statement is the MERGE statement,
which can use the same SET clause syntax as the UPDATE statement to
modify one or more values in existing rows of a table. The MERGE statement
performs an outer join of a source table and a target table, and then
updates rows in the target table with values from the result set of
the join for which the join predicate evaluates to TRUE. Values in
the source table are unchanged by the MERGE statement. Besides updating
rows, the MERGE statement can optionally combine both UPDATE and INSERT
operations, or can combine both DELETE and INSERT operations without
updating any rows. For more information about the syntax and the restrictions
on Update merges, Delete merges, and Insert merges, see the description
of the MERGE statement in the HCL OneDB™ Guide to SQL:
Syntax.