mysql> use one;Database changed mysql> insert into one_table(id,name)values(2,'hhh'); Query OK, 1 row affected (0.03 sec) mysql> select * from one_table; +---+---+ | id | name | +---+---+ | 1 | glt | | 2 | hhh | +---+---+ 2 rows in set (0.00 sec) 1. ...
PostgreSQL外部表(转) 当谈到外部表和数据导入导出时,PostgreSQL提供了一些功能和工具,使得处理外部数据变得更加便捷。让我们逐步介绍这些概念和技术。 外部表(Foreign Tables): 外部表是PostgreSQL中的一个概念,它允许你在数据库中访问和查询外部数据源中的数据,而无需将数据实际复制到数据库中。通过外部表,你可以像查...
bill=# INSERT INTO student(stuname,ctime) SELECT random_text_simple(6),clock_timestamp() FROM generate_series(1,1000000); INSERT 0 1000000 1. 2. 7、查看数据分布 可以看到数据分布还是比较均匀的 bill=# SELECT tableoid::regclass,count(*) from student group by 1 order by 1; tableoid | co...
PostgreSQL Exercises Test Yourself With Exercises Exercise: Choose the correct JOIN clause to select all records from the two tables where there is a match in both tables: SELECT * FROM orders customers ON orders.customer_id = customers.customer_id; Submit Answer » Start the Exercise...
postgres=# select * from pg_class where relname ='db_test'; oid | relname | relnamespace | reltype | reloftype | relowner | relam | relfilenode | reltablespace | relpages | reltuples | relallvisible | reltoastrelid | relhasindex | relisshared | relpersistence | relkind | relnatts...
SQL> pspg select * from user_tables; nushell Thepspgsupports defaulttable_mode:roundedandtable_mode:heavy. The conversion to csv can be used too. sys | get cpu | to csv | pspg --csv Note:footer_modeshould be disabled nushell configuration: ...
我們可以使用 citus_tables 檢視來檢閱分散式資料表的詳細資料,包括其大小:SQL 複製 SELECT * FROM citus_tables; 複製 table_name | citus_table_type | distribution_column | colocation_id | table_size | shard_count | table_owner | access_method ---+---+---+---+---+---+---+--- gi...
-- change distribution column SELECT alter_distributed_table('github_events', distribution_column:='event_id'); -- change shard count of all tables in colocation group SELECT alter_distributed_table('github_events', shard_count:=6, cascade_to_colocated:=true); -- change colocation SELECT alte...
-- change distribution columnSELECTalter_distributed_table('github_events', distribution_column:='event_id');-- change shard count of all tables in colocation groupSELECTalter_distributed_table('github_events', shard_count:=6, cascade_to_colocated:=true);-- change colocationSELECTalter_distributed...
1,标准形式的VACUUM可以和生产数据库操作并行运行(SELECT、INSERT、UPDATE和DELETE等命令将继续正常工作,但在清理期间你无法使用ALTER TABLE等命令来更新表的定义)。 2,VACUUM FULL可以收回更多磁盘空间但是运行起来更慢,且vacuum full不会有后台进程主从触发(只能手动执行)。