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 union all select e.employee_id, CONCAT(e.first_name, ',', e.last_na...
CREATE VIEW:#定义一个查询的视图。 CREATE OR REPLACE VIEW:#如果已经存在一个同名视图,该视图会被替换(限制:只能在原视图基础上增加字段,不能减少字段,且增加字段顺序只能排在最后)。 TEMPORARY|TEMP:#视图被创建为一个临时视图。在当前会话结束时会自动删掉。当临时视图存在时,具有相同名称的已有永久视图对当前会...
create schema schema_test authorization test1 create table tbl_test(a int) create view view_test as select * from tbl_test; 访问模式下数据库对象在模式和数据库对象之间加一个句点即可 school=# select * from schema_test.tbl_test ; a --- (0 rows) school=# select * from schema_test.view_t...
createschemaschema_testauthorizationtest1createtabletbl_test(aint)createviewview_testasselect*fromtbl_test; 访问模式下数据库对象在模式和数据库对象之间加一个句点即可 school=#select*fromschema_test.tbl_test ; a---(0rows) school=#select*fromschema_test.view_test ; a---(0rows) 二、模式修改 语法:...
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 ] ...
1. CREATE OR REPLACE VIEW 按照"CREATE OR REPLACE VIEW" 关键字搜索,这部分代码在ATExecCmd函数(tablecmds.c文件)。可以看到它对应的命令类型叫AT_AddColumnToView,对应操作为调用ATExecAddColumn函数为视图新加列。 /* * ATExecCmd: dispatch a subcommand to appropriate execution routine ...
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...
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...
General \copyright show PostgreSQL usage and distribution terms \crosstabview [COLUMNS] execute query and display result in crosstab \errverbose show most recent error message at maximum verbosity \g [(OPTIONS)] [FILE] execute query (and send result to file or |pipe); \g with...
CREATE VIEW -- define a new view DEALLOCATE -- remove a prepared query DECLARE -- define a cursor DELETE -- delete rows of a table DROP AGGREGATE -- remove a user-defined aggregate function DROP CAST -- remove a user-defined cast DROP CONVERSION -- remove a user-...