create recursive view employee_path(employee_id, employee_name, path) as select employee_id, CONCAT(first_name, ',', last_name), CONCAT(first_name, ',', last_name) as path from employees where manager_id is null
PostgreSQL视图是虚拟表,存储查询语句,节省空间且可控制数据访问。创建视图使用CREATE VIEW,可修改或删除。视图可为自动可更新,但需满足特定条件。触发器用于在特定操作时执行函数,如更新时间或验证数据。合理使用视图和触发器能提升数据库管理效率。
create view v_sensor_realtime_data asselecttb_realtime_data.s_id, tb_realtime_data.sensor_index_code, sensor_value, statistics_status, alarm_time, create_time, seq, sensor_region, tb_sensor.sensor_name from tb_realtime_data leftjointb_sensor on tb_realtime_data.sensor_index_code=tb_sen...
ERROR: cannot refresh materialized view "public.mat_view" concurrently HINT:CreateauniqueindexwithnoWHEREclauseononeormorecolumnsofthematerializedview. 物化视图需要一个唯一的列来支持并发刷新。这意味着您必须确定一个“主键”并创建一个唯一索引: demo=#CREATEUNIQUEINDEXidx_grpONmat_view (grp);CREATEINDEXdem...
postgres=# create index idx2 on t1(name); CREATE INDEX postgres=# create view v1 as select id from t1; CREATE VIE postgres=# alter table t1 add constraint con1 check (id< 2000000); ALTER TABLE create function add(int,int) returns int ...
TABLE, CREATE VIEW, CREATE INDEX, CREATE SEQUENCE, CREATE TRIGGER and GRANT。 IF NOT EXISTS 如果模式已存在,使用该选项不会抛出错误。使用此选项不能使用schema_element子句。 示例 create schema schema_test authorization test1 create table tbl_test(a int) create view view_test as select * from tbl...
ALTER AGGREGATE CREATE VIEW ALTER COLLATION DEALLOCATE ALTER CONVERSION DECLARE ...省略... postgres=# \? 一般性 \copyright 显示PostgreSQL的使用和发行许可条款 \crosstabview [COLUMNS] 执行查询并且以交叉表显示结果 \errverbose 以最冗长的形式显示最近的错误消息 \g [文件...
ClickCreate.To edit existing host entry, click on it's address in theHost addresscolumn and edit theneeded.To delete a host, check the box against it's name, click thebutton.Granted PrivilegesThis option allows to view/edit privileges and grant them to users.To grant a privilege to a ...
CREATE VIEW 定义一个视图。 CREATE [ OR REPLACE ] VIEW name [ ( column_name [, ...] ) ] AS query DEALLOCATE 删除一个准备好的查询。 DEALLOCATE [ PREPARE ] plan_name DECLARE 定义一个游标。 DECLARE name [ BINARY ] [ INSENSITIVE ] [ [ NO ] SCROLL ] ...
CREATE VIEW ProductSum (product_type, cnt_product)AS SELECT product_type, COUNT(*)FROM Product GROUP BY product_type;使⽤视图 可见，如果使⽤视图，不⽤每次都写GROUP BY等⼀些语句从Product表中取数据。并且，如果Product表中数据更新，视图也⾃动更新。这是因为，视图就是保存好的SELECT语句。SEL...