建表語句：
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', '張三');
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");
表數(shù)據(jù)：
數(shù)據(jù)存在則更新數(shù)據(jù)，不存在則插入數(shù)據(jù)
INSERT INTO GOODS VALUES ( 104, '4', '趙六' )
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為必須為唯一主鍵，也可以用下面寫法（注意：必須保證篩選出數(shù)據(jù)唯一）
INSERT INTO GOODS VALUES ( 104, '4', '趙六' )
ON CONFLICT ( STORE_CD, GOOD_CD ) DO
UPDATE
SET NAME = '更新'
WHERE
GOODS.STORE_CD = '104'
AND GOODS.GOOD_CD = '4'
上面的兩種的寫法，是先執(zhí)行insert如果主鍵沖突則執(zhí)行update，沒有沖突就執(zhí)行insert了。要是想先執(zhí)行update語句呢？
update更新失敗執(zhí)行insert，更新成功則執(zhí)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', '趙六'
WHERE NOT EXISTS ( SELECT 1 FROM TABLE1 WHERE STORE_CD = '104' AND GOOD_CD = '4' )
補充：Postgresql插入或更新操作upsert
冪等性的一個要求是多次操作的結果一致。對于update操作，多次直接的結果都是最后update的值，是滿足需求的。但對于insert，如果已經(jīng)插入，第二次會報錯，duplicate error， 主鍵重復或者unique key duplicate。所以需要做一下處理。
最簡單的就是，try-catch，當報錯的時候，調用update去更新，或者策略更簡單點，直接返回就行，不需要更新，以第一條為準。
PostgreSQL從9.5之后就提供了原子的upsert語法： 不存在則插入，發(fā)生沖突可以update。
Inert語法
官方文檔： https://www.postgresql.org/docs/devel/sql-insert.html
[ 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
創(chuàng)建表
CREATE TABLE "test"."upsert_test" (
"id" int4 NOT NULL,
"name" varchar(255) COLLATE "pg_catalog"."default"
)
;
當主鍵id沖突時，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 沖突的主鍵
EXCLUDED 代指要插入的記錄
當主鍵或者unique key發(fā)生沖突時，什么都不做
INSERT INTO test.upsert_test(id, "name")
VALUES(1, 'm'),(2, 'n'),(4, 'c')
ON conflict(id) DO NOTHING;
以上為個人經(jīng)驗，希望能給大家一個參考，也希望大家多多支持腳本之家。如有錯誤或未考慮完全的地方，望不吝賜教。
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