Merging Rows Using MERGE

MERGE statement merges rows from one table into another. MERGE INTO specifies the name of the table to merge the rows into. USING ... ON specifies a table join. WHEN MATCHED THEN tells what to do when the USING...ON is satisfied for a row. WHEN NOT MATCHED THEN tells what to do when the USING...ON is not satisfied for a row.

CREATE TABLE EMP (EMPNO NUMBER(4) NOT NULL,
                  ENAME VARCHAR2(10),
                  JOB VARCHAR2(9),
                  SAL NUMBER(7, 2),
                  DEPTNO NUMBER(2));

INSERT INTO EMP VALUES (5, 'MARTIN','SALESMAN', 1250,    30);
INSERT INTO EMP VALUES (6, 'BLAKE', 'MANAGER',  2850,    30);
INSERT INTO EMP VALUES (7, 'CLARK', 'MANAGER',  2850,    10);
INSERT INTO EMP VALUES (8, 'SCOTT', 'ANALYST',  3000,    20);
INSERT INTO EMP VALUES (9, 'KING',  'PRESIDENT',3000,    10);
INSERT INTO EMP VALUES (10,'TURNER','SALESMAN', 1500,    30);
INSERT INTO EMP VALUES (11,'ADAMS', 'CLERK',    1500,    20);


CREATE TABLE AnotherEMP (EMPNO NUMBER(4) NOT NULL,
                  ENAME VARCHAR2(10),
                  JOB VARCHAR2(9),
                  SAL NUMBER(7, 2),
                  DEPTNO NUMBER(2));

INSERT INTO AnotherEMP VALUES (1, 'SMITH', 'CLERK',     800,    20);
INSERT INTO AnotherEMP VALUES (2, 'ALLEN', 'SALESMAN', 1600,    30);
INSERT INTO AnotherEMP VALUES (3, 'WARD',  'SALESMAN', 1250,    30);
INSERT INTO AnotherEMP VALUES (4, 'JONES', 'MANAGER',  2975,    20);

SQL> MERGE INTO emp p
  2  USING anotherEmp pc ON (p.empno = pc.empno)
  3  WHEN MATCHED THEN
  4  UPDATE
  5     SET p.ename = pc.ename
  6  WHEN NOT MATCHED THEN
  7   INSERT (p.empno, p.ename) VALUES (pc.empno, pc.ename);

4 rows merged.

SQL>
SQL> select * from emp;

     EMPNO ENAME      JOB              SAL     DEPTNO
---------- ---------- --------- ---------- ----------
         5 MARTIN     SALESMAN        1250         30
         6 BLAKE      MANAGER         2850         30
         7 CLARK      MANAGER         2850         10
         8 SCOTT      ANALYST         3000         20
         9 KING       PRESIDENT       3000         10
        10 TURNER     SALESMAN        1500         30
        11 ADAMS      CLERK           1500         20
         4 JONES
         3 WARD
         1 SMITH
         2 ALLEN

11 rows selected.

SQL>