解析postgresql 删除重复数据案例

1.建表
/*
Navicat Premium Data Transfer
Source Server         : localhost
Source Server Type    : PostgreSQL
Source Server Version : 110012
Source Host           : localhost:5432
Source Catalog        : postgres
Source Schema         : public
Target Server Type    : PostgreSQL
Target Server Version : 110012
File Encoding         : 65001
Date: 30/07/2021 10:10:04
*/
-- ----------------------------
-- Table structure for test
-- ----------------------------
DROP TABLE IF EXISTS "public"."test";
CREATE TABLE "public"."test" (
"id" int4 NOT NULL DEFAULT NULL,
"name" varchar(255) COLLATE "pg_catalog"."default" DEFAULT NULL,
"age" int4 DEFAULT NULL
)
;
-- ----------------------------
-- Records of test
-- ----------------------------
INSERT INTO "public"."test" VALUES (1, 'da', 1);
INSERT INTO "public"."test" VALUES (2, 'da', 12);
INSERT INTO "public"."test" VALUES (3, 'dd', 80);
INSERT INTO "public"."test" VALUES (4, 'dd', 80);
INSERT INTO "public"."test" VALUES (5, 'd1', 13);
-- ----------------------------
-- Primary Key structure for table test
-- ----------------------------
ALTER TABLE "public"."test" ADD CONSTRAINT "test_pkey" PRIMARY KEY ("id");
2.根据名称获取重复

先看看哪些数据重复了

select name ,count(1)  from test group by name  having count(1)>1

输出.

name        count
da              2
dd              2
3.删除所有重复数据

注意把要更新的几列数据查询出来做为一个第三方表,然后筛选更新。

delete from test where name in (select t.name from (select name ,count(1)  from test group by name  having count(1)>1) t)
4.保留一行数据

这里展示我们需要保留的数据:重复数据,保留ID最大那一条

SELECT
1.
FROM
test
WHERE
id NOT IN (
( SELECT min( id ) AS id FROM test GROUP BY name )
)
5.删除数据
DELETE
FROM
test
WHERE
id NOT IN (
SELECT
t.id
FROM
( SELECT max( id ) AS id FROM test GROUP BY name ) t
)

到此这篇关于postgresql 删除重复数据案例详解的文章就介绍到这了。

THE END
分享
二维码
< <上一篇
下一篇>>