postgres=#insertintoaa(id)values(3); postgres=#select*fromaawhereagenotin(1,2); id | age ---+--- (0rows) postgres=#select*fromaawhereagenotin(1); id | age ---+--- 2 | 2 (1 row) postgres=# 这就是为什么postgresql对not in查询使用一个特殊的访问方法。 NOT EXISTS 1 2 3 4 ...
在我们平时写SQL时,如果遇到需要排除某些数据时,往往使用id <> xxx and id <> xxx,进而改进为id not in (xxx, xxx); 这样写没有问题,而且简化了SQL,但是往往有些极端情况,使用not in就会造成极大的性能损耗,例如: select * from test where id not in (select id from test_back) and info like '%t...
不幸的是,postgresql优化器不能利用到t_right.value被定义为not null的事实。因此,不可以返回null值。(即not in不能返回null值) 这里可以做一个小测试: postgres=# create table aa(id int,age int);postgres=# insert into aa values(1,1);postgres=# insert into aa values(2,2);postgres=# insert int...
SubLinkType subLinkType;/* see above */intsubLinkId;/* ID (1..n); 0 if not MULTIEXPR */Node *testexpr;/* outer-query test for ALL/ANY/ROWCOMPARE */List *operName;/* originally specified operator name */Node *subselect;/* subselect as Query* or raw parsetree */intlocation;/* to...
问postgresql使用'where not in‘子句优化查询EN数据库优化: 1.可以在单个SQL语句，整个应用程序，单个...
OB 运维 | 一个关于 NOT IN 子查询的 SQL 优化案例 1问题描述 前段时间碰到一个慢 SQL,NOT IN 子查询被优化器改写成了 NESTED-LOOP ANTI JOIN,但是被驱动表全表扫描无法使用索引,执行耗时 16 秒。SQL 如下: 代码语言:javascript 代码运行次数:0
LonwoLonwoadded thex:postgresqllabelNov 21, 2022 Hello@anita970120 It is not clear for now. In the attached file, you have an error: pg_restore: error: could not execute query: ERROR: schema "geo_grid" already exists Command was: CREATE SCHEMA geo_grid; ...
There have been, in the past, bugs in PostgreSQL that could cause data corruption even if the incoming connection was not authenticated. As good policy: Always have PostgreSQL behind a firewall. Ideally, it should have a non-routable private IP address, and only applications that are within ...
postgresql condition Share Improve this question Follow edited Mar 21, 2017 at 11:04 asked Mar 20, 2017 at 15:59 Michal N. 2544 bronze badges Add a comment 2 Answers Sorted by: 4 First, the query you have is not valid. I assume you omitted the GROUP BY a.email when posting...
In this case, the query is failing because the database was created with a custom schema name called "jira". The default schema in postgres is "public", so, when you leave the schema name out of your sql, it will try to search for the table aspublic.cwd_user. ...