1.建表
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/* 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
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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。
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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
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SELECT 1. FROM test WHERE id NOT IN ( ( SELECT min( id ) AS id FROM test GROUP BY name ) ) |
5.删除数据
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DELETEFROM test WHERE id NOT IN ( SELECT t.id FROM ( SELECT max( id ) AS id FROM test GROUP BY name ) t ) |
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原文链接：https://blog.csdn.net/weixin_43632687/article/details/119239104
