数据库技术:PostgreSQL的upsert实例操作(insert on conflict do)

建表语句:

drop table if exists \”goods\”; create table \”goods\” ( \”store_cd\” int4 not null, \”good_cd\” varchar(50) collate \”pg_catalog\”.\”default\” not null, \”name\” varchar(255) collate \”pg_catalog\”.\”default\” ); insert into \”goods\” values (101, \’1\’, \’张三\’); insert into \”goods\” values (102, \’2\’, \’李四\’); insert into \”goods\” values (103, \’3\’, \’王五\’); alter table \”goods\” add constraint \”pr_cd_key\” primary key (\”store_cd\”, \”good_cd\”);

表数据:

20210531_60b55d9195f3a

数据存在则更新数据,不存在则插入数据

insert into goods values ( 104, \’4\’, \’赵六\’ ) on conflict on constraint pr_key_cd do update set name = \’更新\’ where goods.store_cd = \’104\’ and goods.good_cd = \’4\’

pr_key_cd为必须为唯一主键,也可以用下面写法(注意:必须保证筛选出数据唯一)

insert into goods values ( 104, \’4\’, \’赵六\’ ) on conflict ( store_cd, good_cd ) do update set name = \’更新\’ where goods.store_cd = \’104\’ and goods.good_cd = \’4\’

上面的两种的写法,是先执行insert如果主键冲突则执行update,没有冲突就执行insert了。要是想先执行update语句呢?

update更新失败执行insert,更新成功则执行update。

with table1 as ( update goods set name = \’更新\’ where store_cd = \’104\’ and good_cd = \’4\’ returning * ) insert into goods select 104, \’4\’, \’赵六\’ where not exists ( select 1 from table1 where store_cd = \’104\’ and good_cd = \’4\’ )

补充:postgresql插入或更新操作upsert

幂等性的一个要求是多次操作的结果一致。对于update操作,多次直接的结果都是最后update的值,是满足需求的。但对于insert,如果已经插入,第二次会报错,duplicate error, 主键重复或者unique key duplicate。所以需要做一下处理。

最简单的就是,try-catch,当报错的时候,调用update去更新,或者策略更简单点,直接返回就行,不需要更新,以第一条为准。

postgresql从9.5之后就提供了原子的upsert语法: 不存在则插入,发生冲突可以update。

inert语法

官方文档:

[ with [ recursive ] with_query [, …] ] insert into table_name [ as alias ] [ ( column_name [, …] ) ] [ overriding { system | user} value ] { default values | values ( { expression | default } [, …] ) [, …] | query } [ on conflict [ conflict_target ] conflict_action ] [ returning * | output_expression [ [ as ] output_name ] [, …] ] where conflict_target can be one of: ( { index_column_name | ( index_expression ) } [ collate collation ] [ opclass ] [, …] ) [ where index_predicate ] on constraint constraint_name and conflict_action is one of: do nothing do update set { column_name = { expression | default } | ( column_name [, …] ) = [ row ] ( { expression | default } [, …] ) | ( column_name [, …] ) = ( sub-select ) } [, …] [ where condition ]

index_column_name

the name of a table_name column. used to infer arbiter indexes. follows create index format. select privilege on index_column_name is required.

index_expression

similar to index_column_name, but used to infer expressions on table_name columns appearing within index definitions (not simple columns). follows create index format. select privilege on any column appearing within index_expression is required.

使用示例

创建表

create table \”test\”.\”upsert_test\” ( \”id\” int4 not null, \”name\” varchar(255) collate \”pg_catalog\”.\”default\” ) ;

当主键id冲突时,更新其他字段

insert into test.upsert_test(id, \”name\”) values(1, \’m\’),(2, \’n\’),(4, \’c\’) on conflict(id) do update set \”name\” = excluded.name;

did 冲突的主键

excluded 代指要插入的记录

当主键或者unique key发生冲突时,什么都不做

insert into test.upsert_test(id, \”name\”) values(1, \’m\’),(2, \’n\’),(4, \’c\’) on conflict(id) do nothing;

以上为个人经验,希望能给大家一个参考,也希望大家多多支持。如有错误或未考虑完全的地方,望不吝赐教。

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