Oracle merge 与 PG新特性 UPSERT
PostgreSQL 9.5于2016年1月7日正式发布，其中包含新特性“UPSERT”(INSERT, ON CONFLICT UPDATE),
即：插入数据，正常时写入，主键冲突时更新。
Oracle的 merge into 转化为 -- >
PostgreSQL 的 INSERT INTO ... ON CONFLICT .. update...
下面简单测试下：
一、Oracle数据库:
1、创建表t1、t2，插入数据：
SQL> create table t1 (id int constraint idx_t1_id primary key,name varchar(20) constraint con_name not null);
Table created.
SQL> insert into t1 values(1,'jason');
1 row created.
SQL> insert into t1 values(2,'lucy');
1 row created.
SQL> commit;
Commit complete.
SQL> create table t2 (id int constraint idx_t2_id primary key,name varchar(20) constraint con_t2_name not null);
Table created.
SQL>
SQL> insert into t2 values(1,'jason');
insert into t2 values(3,'jack');
insert into t2 values(4,'david');
insert into t2 values(5,'jacy');
insert into t2 values(6,'switty');
1 row created.
SQL>
1 row created.
SQL>
1 row created.
SQL>
1 row created.
SQL>
1 row created.
SQL>
SQL> commit;
Commit complete.
SQL> select * from t1;
ID NAME
---------- --------------------
1 jason
2 lucy
SQL> select * from t2;
ID NAME
---------- --------------------
1 jason
3 jack
4 david
5 jacy
6 switty
2、merge into 将表t2数据合并到t1中
SQL> MERGE INTO t1
USING (SELECT id,name FROM t2) t2
ON ( t1.id=t2.id)
WHEN MATCHED THEN
UPDATE SET T1.name= t2.name
WHEN NOT MATCHED THEN
INSERT (id,name) VALUES (t2.id,t2.name);
5 rows merged.
SQL> select * from t1;
ID NAME
---------- --------------------
1 jason
2 lucy
3 jack
4 david
5 jacy
6 switty
6 rows selected.
SQL>
二、PostgreSQL 数据库：
1、创建表t1、t2 :
postgres=# create table t1 (id int constraint idx_t1_id primary key,name varchar(20) constraint con_name not null);
CREATE TABLE
postgres=#
postgres=#
postgres=# \d t1
Table "public.t1"
Column | Type | Collation | Nullable | Default
--------+-----------------------+-----------+----------+---------
id | integer | | not null |
name | character varying(20) | | not null |
Indexes:
"idx_t1_id" PRIMARY KEY, btree (id)
postgres=# insert into t1 values(1,'jason');
INSERT 0 1
postgres=# insert into t1 values(2,'lucy');
INSERT 0 1
postgres=# select * from t1;
id | name
----+-------
1 | jason
2 | lucy
(2 rows)
postgres=# create table t2 (id int constraint idx_t2_id primary key,name varchar(20) constraint con_t2_name not null);
CREATE TABLE
postgres=# insert into t2 values(1,'jason');
INSERT 0 1
postgres=# insert into t2 values(3,'jack');
INSERT 0 1
postgres=# insert into t2 values(4,'david');
INSERT 0 1
postgres=# insert into t2 values(5,'jacy');
INSERT 0 1
postgres=# insert into t2 values(6,'switty');
INSERT 0 1
postgres=#
postgres=#
postgres=# select * from t2;
id | name
----+--------
1 | jason
3 | jack
4 | david
5 | jacy
6 | switty
(5 rows)
2、使用insert into ... ON CONFLICT do UPDATE ...
postgres=# insert into t1 select id,name from t2 ON CONFLICT(id) do update set name=excluded.name where t1.id=excluded.id;
INSERT 0 5
postgres=# select * from t1;
id | name
----+--------
2 | lucy
1 | jason
3 | jack
4 | david
5 | jacy
6 | switty
(6 rows)
附：
-------------------------------------------------------------------------------
当有主键冲突时，也可以选择do nothing
postgres=# insert into t1 select id,name from t2 ON CONFLICT(id) do update set name=excluded.name where t1.id=excluded.id;
INSERT 0 5
postgres=# insert into t1 select id,name from t2 ON CONFLICT(id) do nothing;
INSERT 0 0
postgres=#
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