CEATE TABLE是创建一个新表 CREATE TABLE AS 和 SELECT * INTO:CREATE TABLE AS 是被推荐的语法,因为这种形式的SELECT INTO在ECPG 或PL/pgSQL中不可用,因为它们对 INTO子句的解释不同。 CREATE TABLE employees_202311191058 ( like employees) 使用时需要注意,原表的建表语句中如果有字段使用 “serial4” 则使...
如果你不希望EXPLAIN影响真正数据,在执行INSERT, UPDATE, DELETE, MERGE, CREATE TABLE AS 或EXECUTE语句时,可以将EXPLAIN ANALYZE放到一个事务中,执行完毕后回滚。命令如下: BEGIN; EXPLAIN ANALYZE ...; ROLLBACK; 此外,ANALYZE VERBOSE选项的顺序不能交换: explain analyze verbose select * from custom; --- ...
postgres=# postgres=# create extension pageinspect; CREATE EXTENSION postgres=# create table t as select generate_series(1,100)a; 我这里创建了一个对应的插件,并且创建了一个表。 然后可以通过 pageinspect 插件的一些函数查看表所属的 page 的数据信息: postgres=# select * from page_header(get_raw_pa...
CREATETABLEtbl ( col1int, col2int);INSERTINTOtblSELECTi/10000, i/100000FROMgenerate_series (1,10000000) s(i); ANALYZE tbl;select*frompg_statswheretablename='tbl'andattname='col1';-[RECORD 1]---+---schemaname|publictablename|tbl attname|col1 inherited|f null_frac|0avg_width|4n_dist...
ALTER TABLE test002 CHECK CONSTRAINT CK_test002_phone--重新启用这个约束。 1. 2. 3. 4. 5. 6. 7. 规则和默认值: 规则创建:create rule <rule name> AS <expression>. CREATE RULE Salary AS @Salary>0; --创建规则 --查看规则:exec sp_helptext <rule name>;会显示文本信息 ...
-- 创建定时器CREATEORREPLACEFUNCTIONcollect_data()RETURNSVOIDAS$$BEGIN-- 在此处编写数据采集逻辑RAISE NOTICE'Data collection completed at %',CURRENT_TIMESTAMP;END;$$LANGUAGEplpgsql;-- 创建定时任务CREATEEVENTTRIGGERcollect_data_triggerONSCHEDULE EVERY'1 day'DOEXECUTEPROCEDUREcollect_data(); ...
table using the same keyCREATEORREPLACEFUNCTIONaudit_trigger()RETURNStriggerAS $$DECLAREBEGININSERTINTOdata_auditVALUES(TG_OP,Coalesce(OLD.key,NEW.key),NEW.value);RETURNNULL;END;$$LANGUAGEplpgsql;--so,it is safe to enable triggers on distributed tablesSET citus.enable_unsafe_triggersTOon;CREATE...
creat table t4 as select*from t3 切换日志; select pg_switch_wal(); 关闭数据库; pg_ctl stop 用pg_rman做时间点恢复 pg_rman restore–recovery-target-time=“2022-04-1102:41:49” 同时会自动生成一个recovery.conf文件。 启动数据库,执行函数,把只读模式改成读写模式; ...
第三种方法是注意系统ANALYZE命令，它定期执行autovacuum进程，从PostgreSQL 8.3开始更新表统计信息，也可以...
These statements, which are often referred to as Common Table Expressions or CTEs, can be thought of as defining temporary tables that exist just for one query. WITH提供了一种编写辅助语句以便在更大的查询中使用的方法。这些语句(通常称为公用表表达式或CTE)可以被视为定义仅针对一个查询存在的临时表...