SQL标准于2003年增加了一个新的数据操作语句：MERGE（合并），它可以同时完成INSERT语句和UPDATE语句，甚至DELETE语句的操作。
标准合并语句
它的基本语法如下：
MERGE INTO target [AS t_alias]
USING source_table [AS s_alias]
ON (conditions)
WHEN MATCHED THEN
UPDATE
SET col1 = expr1,
col2 = expr2,
...
WHEN NOT MATCHED THEN
INSERT (col1, col2,...)
VALUES (expr1, expr2...);其中，target_table是合并操作的目标表。
USING子句指定了数据源，可以是一个表或者查询语句。
ON子句指定了数据合并的条件，通常使用主键或者唯一键相等作为合并的条件。
对于数据源中的每条记录，如果目标表中存在匹配的记录，则执行WHEN MATCHED THEN分支的更新操作；如果目标表中不存在匹配的记录，则执行WHEN NOT MATCHED THEN分支的插入操作。
案例分析
案例使用的示例表
下面的操作会用到两个表，其中employee表中存储了员工的基本信息，包括姓名、入职日期、部门编号、薪资等字段。以下是该表中的部分数据：
emp_devp表是employee的备份表。
这两个表的初始化脚本可以在文章底部获取。
示例一
使用MERGE语句将employee表中dept_id为4的员工信息合并到emp_devp表中：
MERGE INTO emp_devp t
USING (SELECT emp_id, emp_name, sex, dept_id, manager,
hire_date, job_id, salary, bonus, email
FROM employee
WHERE dept_id = 4) s
ON (t.emp_id = s.emp_id)
WHEN MATCHED THEN
UPDATE
SET t.emp_name = s.emp_name,
t.sex = s.sex, t.dept_id = s.dept_id, t.manager = s.manager,
t.hire_date = s.hire_date, t.job_id = s.job_id,
t.salary = s.salary, t.bonus = s.bonus, t.email = s.email
WHEN NOT MATCHED THEN
INSERT (emp_id, emp_name, sex, dept_id, manager,
hire_date, job_id, salary, bonus, email)
VALUES (s.emp_id, s.emp_name, s.sex, s.dept_id, s.manager,
s.hire_date, s.job_id, s.salary, s.bonus, s.email);以上合并操作的判断条件为数据源和目标表中的emp_id是否相等。如果相等，则更新目标表中的数据；否则，插入数据到目标表。
第一次运行以上语句时，emp_devp表中没有任何数据，因此对于数据源中的每条记录都会执行WHEN NOT MATCHED THEN分支，也就是插入数据。
以上语句执行成功之后，我们可以查看合并后的数据：
示例二
MERGE语句还支持DELETE子句，可以用于删除目标表中匹配的数据，例如：
MERGE INTO emp_devp t
USING (SELECT emp_id, emp_name, sex, dept_id, manager,
hire_date, job_id, salary, bonus, email
FROM employee
WHERE dept_id = 4) s
ON (t.emp_id = s.emp_id)
WHEN MATCHED THEN
UPDATE
SET t.emp_name = s.emp_name,
t.sex = s.sex, t.dept_id = s.dept_id, t.manager = s.manager,
t.hire_date = s.hire_date, t.job_id = s.job_id,
t.salary = s.salary, t.bonus = s.bonus, t.email = s.email
DELETE WHERE t.emp_name = '赵氏'
WHEN NOT MATCHED THEN
INSERT (emp_id, emp_name, sex, dept_id, manager,
hire_date, job_id, salary, bonus, email)
VALUES (s.emp_id, s.emp_name, s.sex, s.dept_id, s.manager,
s.hire_date, s.job_id, s.salary, s.bonus, s.email);我们在WHEN MATCHED THEN分支中增加了一个DELETE子句和一个WHERE条件。
如果运行以上语句，emp_devp表中姓名为“赵氏”的员工记录将会被删除。
通过查询，发现emp_name为“赵氏”的记录被删除了。
示例表和脚本
--员工信息表
CREATE TABLE employee
( emp_id NUMBER
, emp_name VARCHAR2(50) NOT NULL
, sex VARCHAR2(10) NOT NULL
, dept_id INTEGER NOT NULL
, manager INTEGER
, hire_date DATE NOT NULL
, job_id INTEGER NOT NULL
, salary NUMERIC(8,2) NOT NULL
, bonus NUMERIC(8,2)
, email VARCHAR2(100) NOT NULL
, comments VARCHAR2(500)
, create_by VARCHAR2(50) NOT NULL
, create_ts TIMESTAMP NOT NULL
, update_by VARCHAR2(50)
, update_ts TIMESTAMP
) ;
COMMENT ON TABLE employee IS '员工信息表';
COMMENT ON COLUMN employee.emp_id IS '员工编号，自增主键';
COMMENT ON COLUMN employee.emp_name IS '员工姓名';
COMMENT ON COLUMN employee.sex IS '性别';
COMMENT ON COLUMN employee.dept_id IS '部门编号';
COMMENT ON COLUMN employee.manager IS '上级经理';
COMMENT ON COLUMN employee.hire_date IS '入职日期';
COMMENT ON COLUMN employee.job_id IS '职位编号';
COMMENT ON COLUMN employee.salary IS '月薪';
COMMENT ON COLUMN employee.bonus IS '年终奖金';
COMMENT ON COLUMN employee.email IS '电子邮箱';
COMMENT ON COLUMN employee.comments IS '备注信息';
COMMENT ON COLUMN employee.create_by IS '创建者';
COMMENT ON COLUMN employee.create_ts IS '创建时间';
COMMENT ON COLUMN employee.update_by IS '修改者';
COMMENT ON COLUMN employee.update_ts IS '修改时间';
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (1,'刘备', '男', 1, NULL, DATE '2000-01-01', 1, 30000, 10000, '[email protected]', NULL, 'Admin', TIMESTAMP '2000-01-01 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (2,'关羽', '男', 1, 1, DATE '2000-01-01', 2, 26000, 10000, '[email protected]', NULL, 'Admin', TIMESTAMP '2000-01-01 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (3,'张飞', '男', 1, 1, DATE '2000-01-01', 2, 24000, 10000, '[email protected]', NULL, 'Admin', TIMESTAMP '2000-01-01 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (4,'诸葛亮', '男', 2, 1, DATE '2006-03-15', 3, 24000, 8000, '[email protected]', NULL, 'Admin', TIMESTAMP '2006-03-15 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (5,'黄忠', '男', 2, 4, DATE '2008-10-25', 4, 8000, NULL, '[email protected]', NULL, 'Admin', TIMESTAMP '2008-10-25 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (6,'魏延', '男', 2, 4, DATE '2007-04-01', 4, 7500, NULL, '[email protected]', NULL, 'Admin', TIMESTAMP '2007-04-01 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (7,'孙尚香', '女', 3, 1, DATE '2002-08-08', 5, 12000, 5000, '[email protected]', NULL, 'Admin', TIMESTAMP '2002-08-08 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (8,'孙丫鬟', '女', 3, 7, DATE '2002-08-08', 6, 6000, NULL, '[email protected]', NULL, 'Admin', TIMESTAMP '2002-08-08 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (9,'赵云', '男', 4, 1, DATE '2005-12-19', 7, 15000, 6000, '[email protected]', NULL, 'Admin', TIMESTAMP '2005-12-19 10:00:00', 'Admin', TIMESTAMP '2006-12-31 10:00:00');
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (10,'廖化', '男', 4, 9, DATE '2009-02-17', 8, 6500, NULL, '[email protected]', NULL, 'Admin', TIMESTAMP '2009-02-17 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (11,'关平', '男', 4, 9, DATE '2011-07-24', 8, 6800, NULL, '[email protected]', NULL, 'Admin', TIMESTAMP '2011-07-24 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (12,'赵氏', '女', 4, 9, DATE '2011-11-10', 8, 6600, NULL, '[email protected]', NULL, 'Admin', TIMESTAMP '2011-11-10 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (13,'关兴', '男', 4, 9, DATE '2011-07-30', 8, 7000, NULL, '[email protected]', NULL, 'Admin', TIMESTAMP '2011-07-30 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (14,'张苞', '男', 4, 9, DATE '2012-05-31', 8, 6500, NULL, '[email protected]', NULL, 'Admin', TIMESTAMP '2012-05-31 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (15,'赵统', '男', 4, 9, DATE '2012-05-03', 8, 6000, NULL, '[email protected]', NULL, 'Admin', TIMESTAMP '2012-05-03 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (16,'周仓', '男', 4, 9, DATE '2010-02-20', 8, 8000, NULL, '[email protected]', NULL, 'Admin', TIMESTAMP '2010-02-20 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (17,'马岱', '男', 4, 9, DATE '2014-09-16', 8, 5800, NULL, '[email protected]', NULL, 'Admin', TIMESTAMP '2014-09-16 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (18,'法正', '男', 5, 2, DATE '2017-04-09', 9, 10000, 5000, '[email protected]', NULL, 'Admin', TIMESTAMP '2017-04-09 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (19,'庞统', '男', 5, 18, DATE '2017-06-06', 10, 4100, 2000, '[email protected]', NULL, 'Admin', TIMESTAMP '2017-06-06 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (20,'蒋琬', '男', 5, 18, DATE '2018-01-28', 10, 4000, 1500, '[email protected]', NULL, 'Admin', TIMESTAMP '2018-01-28 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (21,'黄权', '男', 5, 18, DATE '2018-03-14', 10, 4200, NULL, '[email protected]', NULL, 'Admin', TIMESTAMP '2018-03-14 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (22,'糜竺', '男', 5, 18, DATE '2018-03-27', 10, 4300, NULL, '[email protected]', NULL, 'Admin', TIMESTAMP '2018-03-27 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (23,'邓芝', '男', 5, 18, DATE '2018-11-11', 10, 4000, NULL, '[email protected]', NULL, 'Admin', TIMESTAMP '2018-11-11 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (24,'简雍', '男', 5, 18, DATE '2019-05-11', 10, 4800, NULL, '[email protected]', NULL, 'Admin', TIMESTAMP '2019-05-11 10:00:00', NULL, NULL);
INSERT INTO employee(EMP_ID,emp_name, sex, dept_id, manager, hire_date, job_id, salary, bonus, email, comments, create_by, create_ts, update_by, update_ts) VALUES (25,'孙乾', '男', 5, 18, DATE '2018-10-09', 10, 4700, NULL, '[email protected]', NULL, 'Admin', TIMESTAMP '2018-10-09 10:00:00', NULL, NULL);
--员工信息表备份表
CREATE TABLE emp_devp
( emp_id NUMBER
, emp_name VARCHAR2(50) NOT NULL
, sex VARCHAR2(10) NOT NULL
, dept_id INTEGER NOT NULL
, manager INTEGER
, hire_date DATE NOT NULL
, job_id INTEGER NOT NULL
, salary NUMERIC(8,2) NOT NULL
, bonus NUMERIC(8,2)
, email VARCHAR2(100) NOT NULL
) ;
COMMENT ON TABLE emp_devp IS '员工信息表备份表';
COMMENT ON COLUMN emp_devp.emp_id IS '员工编号，自增主键';
COMMENT ON COLUMN emp_devp.emp_name IS '员工姓名';
COMMENT ON COLUMN emp_devp.sex IS '性别';
COMMENT ON COLUMN emp_devp.dept_id IS '部门编号';
COMMENT ON COLUMN emp_devp.manager IS '上级经理';
COMMENT ON COLUMN emp_devp.hire_date IS '入职日期';
COMMENT ON COLUMN emp_devp.job_id IS '职位编号';
COMMENT ON COLUMN emp_devp.salary IS '月薪';
COMMENT ON COLUMN emp_devp.bonus IS '年终奖金';
COMMENT ON COLUMN emp_devp.email IS '电子邮箱';