column2 DESC, ...][OFFSET m {ROW | ROWS}][FETCH { FIRST | NEXT } [ num_rows]{ ROW|ROWS }ONLY];SELECTcolumn1, column2, ...FROMtable[WHERE conditions][ORDER BY column1 ASC, column2 DESC, ...][LIMIT { num_rows| ALL }][OFFSET m {ROW | ROWS}]; ...
SELECT pg_database.datnameas"database_name", pg_database_size(pg_database.datname)/1024/1024/1024AS size_in_GB FROM pg_database ORDER by size_in_GB DESC; database_name|size_in_gb---+---mumbai|422template1|0template0|0(3rows) 使用元命令获取 Postgres 中所有数据库及其大小的列表 nel...
PostgreSQL SELECT 语句用于从数据库中选取数据。结果被存储在一个结果表中,称为结果集。语法SELECT 语句语法格式如下:SELECT column1, column2,...columnN FROM table_name;column1, column2,...columnN 为表中字段名。 table_name 为表名。如果我们想读取表中的所有数据可以使用以下 SQL 语句:SELECT * FROM...
* for all commandsQuery Buffer \e [FILE] [LINE] edit the query buffer (or file) with external editor \ef [FUNCNAME [LINE]] edit function definition with external editor...Informational (options: S = show system objects, + = additional detail) ...
例如,我们查看下 select 语句的语法:postgres=# \help SELECT Command: SELECT Description: retrieve rows from a table or view Syntax: [ WITH [ RECURSIVE ] with_query [, ...] ] SELECT [ ALL | DISTINCT [ ON ( expression [, ...] ) ] ] [ * | expression [ [ AS ] output_name ] [...
SELECT COUNT(*) FROM people WHERE inpgconn2018 = 'Y'; 没有开并行的情况下(max_parallel_workers_per_gather=0),查询计划如下: Aggregate (cost=169324.73..169324.74 rows=1 width=8) (actual time=983.729..983.730 rows=1 loops=1) -> Seq Scan on people (cost=0.00..169307.23 rows=7001 width=...
postgres=# select * from tdsql_pg union all select * from t_appoint_col; id | nickname ---+--- 1 | hello tdsql_pg 2 | tdsql_pg好 1 | tdsql_pg分布式数据库的时代来了 1 | hello tdsql_pg (4 rows) 过滤重复的记录。 postgres=# select * from tdsql_pg union select * from t...
postgres=# explain select *from test; -[ RECORD 1 ]--- QUERY PLAN | Seq Scan on test (cost=0.00..35.50 rows=2550 width=4) 得到json格式的执行计划。 postgres=# explain(format json) select *from test; -[ RECORD 1 ]--- QUERY PLAN | [ + | { + | "Plan": { + | "Node Type...
sql 5) 删除数据库dropdb db1 dropdb db2 6) 恢复数据库 psql < db_all.sql #如果遇到当前有数据库或者表,会提示表已经存在,数据照常导入。psql –f db_all.sql 7) 查看数据库 db1 是否恢复 psql db1 testdb=# select * from tb1; a --- 1 (1 rows) 8) 查看数据库 db2 是否恢复 psql db2 ...
cursor.execute("SELECT * FROM employees;")rows=cursor.fetchall()forrowinrows:print(row)# 关闭游标和连接cursor.close()connection.close() 1. 2. 3. 4. 5. 6. 7. 8. 9. 关系图(ER图) 以下是我们在数据库中使用的表的关系图: EMPLOYEESintegeridPK员工IDstringname员工姓名decimalsalary员工薪水 ...