在PostgreSQL中,可以使用命名查询(Named Query)来为查询赋予一个别名,以便在需要时可以快速地调用。要在PostgreSQL中创建一个命名查询,可以使用以下步骤: 使用CREATE OR REPLACE VIEW语句创建一个视图,该视图将包含所需的查询。 例如,如果您要创建一个名为“employees_over_30”的命名查询,可以使用以下SQL语句
CREATE OR REPLACE VIEW my_view AS SELECT id, name FROM my_table; 参考链接 PostgreSQL Documentation - Views PostgreSQL Documentation - System Catalogs 通过以上步骤,您应该能够诊断并解决Postgres重新启动后视图丢失的问题。如果问题仍然存在,建议查看详细的日志文件以获取更多线索。 相关搜索: 升级后Postgres扩展...
--3.带参函数(out是输出参数),如果有输出函数,就不能用select语句测试了,就得用匿名块测试了 create or replace function maxNum(v_num1 in number,v_num2 in number,v_r out number)---in是输入参数,可以不写。out是输出参数 return number is v_max number;---用来接收返回值 begin if v_num1>v...
创建一个视图 CREATEORREPLACEVIEWstudent_view ASSELECT*FROMstudentLEFTJOINteacherONstudent.teacher_id=teacher.id; 创建一个物化视图 CREATEMATERIALIZEDVIEWstudent_view_m ASSELECT*FROMstudentLEFTJOINteacherONstudent.teacher_id=teacher.id; student_view去每个表中进行查询,而student_view_m 直接去视图表查询,而...
CREATEORREPLACEVIEWemployee_viewASSELECTemployee_name, salaryFROMemployees; 4.3 数据转换 在使用USING子句进行数据类型转换时,确保转换表达式能够正确处理现有数据。例如,将日期格式的文本转换为DATE类型时,确保文本的格式与目标数据类型兼容。 示例: ALTERTABLEemployeesALTERCOLUMNhire_date TYPEDATEUSINGTO_DATE(hire_dat...
CREATEORREPLACEVIEWstudent_viewASSELECT*FROMstudentLEFTJOINteacherONstudent.teacher_id=teacher.id; 创建一个物化视图 CREATEMATERIALIZEDVIEWstudent_view_mASSELECT*FROMstudentLEFTJOINteacherONstudent.teacher_id=teacher.id; 进行查询explain: master=>explainselect*fromstudent_view; ...
CREATEORREPLACEVIEWemployee_viewASSELECTemployee_name, emp_idFROMemployees; 3.2 更新索引和约束 如果列在索引或约束中被使用,通常不需要对这些对象进行额外操作,因为 PostgreSQL 会自动更新这些引用。然而,确认没有因列重命名而导致性能问题或功能障碍是一个好习惯。
create viewis currently used. My Environment Relevant Database Driver(s) Agree, can't see any reason not to useCREATE OR REPLACEoverCREATE. Currently the fact that views (as far as I can tell) are only changed using create or drop statements can cause migrations to fail and require manuall...
CREATE OR REPLACE VIEW student_view AS SELECT * FROM student LEFT JOIN teacher ON student.teacher_id = ; 1. 2. 3. 4. 5. 创建一个物化视图 CREATE MATERIALIZED VIEW student_view_m AS SELECT * FROM student LEFT JOIN teacher ON student.teacher_id = ; ...
CREATE [ OR REPLACE ] VIEW <name> [ ( <column_name> [, ...] ) ] AS <query> Description CREATE VIEW defines a view of a query. The view isn't physically materialized. Instead, the query runs every time a query references the view. CREATE OR REPLACE VIEW is similar. H...