|Oracle9i SQL Reference
Release 2 (9.2)
Part Number A96540-01
SQL Statements: DROP SEQUENCE to ROLLBACK, 15 of 19
MERGE statement to select rows from one table for update or insertion into another table. The decision whether to update or insert into the target table is based on a condition in the
This statement is a convenient way to combine at least two operations. It lets you avoid multiple
UPDATE DML statements.
MERGE is a deterministic statement. That is, you cannot update the same row of the target table multiple times in the same
You must have
UPDATE object privileges on the target table and
SELECT privilege on the source table.
INTO clause to specify the target table you are updating or inserting into.
USING clause to specify the source of the data to be updated or inserted. The source can be a table, view, or the result of a subquery.
ON clause to specify the condition upon which the
MERGE operation either updates or inserts. For each row in the target table for which the search condition is true, Oracle updates the row based with corresponding data from the source table. If the condition is not true for any rows, then Oracle inserts into the target table based on the corresponding source table row.
Use these clauses to instruct Oracle how to respond to the results of the join condition in the
ON clause. You can specify these two clauses in either order.
merge_update_clause specifies the new column values of the target table. Oracle performs this update if the condition of the
ON clause is true. If the update clause is executed, then all update triggers defined on the target table are activated.
Restriction on updating a view: You cannot specify
DEFAULT when updating a view.
merge_insert_clause specifies values to insert into the column of the target table if the condition of the
ON clause is false. If the insert clause is executed, then all insert triggers defined on the target table are activated.
Restriction on merging into a view: You cannot specify
DEFAULT when updating a view.
The following example creates a
bonuses table in the sample schema
oe with a default bonus of 100. It then inserts into the
bonuses table all employees who made sales (based on the
sales_rep_id column of the
oe.orders table). Finally, the Human Resources manager decides that all employees should receive a bonus. Those who have not made sales get a bonus of 1% of their salary. Those who already made sales get an increase in their bonus equal to 1% of their salary. The
MERGE statement implements these changes in one step:
CREATE TABLE bonuses (employee_id NUMBER, bonus NUMBER DEFAULT 100); INSERT INTO bonuses(employee_id) (SELECT e.employee_id FROM employees e, orders o WHERE e.employee_id = o.sales_rep_id GROUP BY e.employee_id); SELECT * FROM bonuses; EMPLOYEE_ID BONUS ----------- ---------- 153 100 154 100 155 100 156 100 158 100 159 100 160 100 161 100 163 100 MERGE INTO bonuses D USING (SELECT employee_id, salary, department_id FROM employees WHERE department_id = 80) S ON (D.employee_id = S.employee_id) WHEN MATCHED THEN UPDATE SET D.bonus = D.bonus + S.salary*.01 WHEN NOT MATCHED THEN INSERT (D.employee_id, D.bonus) VALUES (S.employee_id, S.salary*0.1); EMPLOYEE_ID BONUS ----------- ---------- 153 180 154 175 155 170 156 200 158 190 159 180 160 175 161 170 163 195 157 950 145 1400 170 960 179 620 152 900 169 1000 . . .