建表语句：
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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：
数据存在则更新数据，不存在则插入数据
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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）
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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。
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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： https://www.postgresql.org/docs/devel/sql-insert.html
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[ 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
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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
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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
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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服务器之家。如有错误或未考虑完全的地方，望不吝赐教。
原文链接：https://yunan.blog.csdn.net/article/details/100897511
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