Change Existing Data

Use the update command to change single rows, groups of rows, or all rows in a table. As in all data modification statements, you can change the data in only one table at a time.

update specifies the row or rows you want changed and the new data. The new data can be a constant or an expression that you specify, or data pulled from other tables.

If an update statement violates an integrity constraint, the update does not take place and an error message is generated. The update is canceled, for example, if it affects the table’s IDENTITY column, or if one of the values being added is the wrong datatype, or if it violates a rule that has been defined for one of the columns or datatypes involved.

SAP ASE does not prevent you from issuing an update command that updates a single row more than once. However, because of the way that update is processed, updates from a single statement do not accumulate. That is, if an update statement modifies the same row twice, the second update is not based on the new values from the first update but on the original values. The results are unpredictable, since they depend on the order of processing.

See the Reference Manual: Commands.

• Use the set Clause with Update
  The set clause specifies columns and changed values. The where clause determines which rows are to be updated. If you do not include the where clause, the specified columns of all the rows are updated with the values provided in the set clause.
• Use the where Clause with update
  The where clause specifies which rows are to be updated.
• Use the from Clause with update
  Use the from clause to add data from one or more tables into the table you are updating.
• Perform updates with joins
  You can use update to join columns when the columns being joined have the same or compatible datatypes.
• Update IDENTITY Columns
  You can use the syb_identity keyword, qualified by the table name, where necessary, to update an IDENTITY column.