您可以通过提供另一个名称来临时重命名表或列,该名称称为 ALIAS ,重命名是一个临时更改,数据库中的实际表名不会更改。
列别名用于重命名表的列,以用于特定的PostgreSQL查询。
table 别名的基本语法如下-
SELECT column1, column2.... FROM table_name AS alias_name WHERE [condition];
column 别名的基本语法如下-
SELECT column_name AS alias_name FROM table_name WHERE [condition];
考虑以下两个表,(a) COMPANY 表如下-
testdb=# select * from COMPANY; id | name | age | address | salary ----+-------+-----+-----------+-------- 1 | Paul | 32 | California| 20000 2 | Learnfk | 25 | Texas | 15000 3 | Teddy | 23 | Norway | 20000 4 | Mark | 25 | Rich-Mond | 65000 5 | David | 27 | Texas | 85000 6 | Kim | 22 | South-Hall| 45000 7 | James | 24 | Houston | 10000 (7 rows)
(b)另一个表是 DEPARTMENT 如下-
id | dept | emp_id ----+--------------+-------- 1 | IT Billing | 1 2 | Engineering | 2 3 | Finance | 7 4 | Engineering | 3 5 | Finance | 4 6 | Engineering | 5 7 | Finance | 6 (7 rows)
现在,下面是 TABLE别名的用法,无涯教程分别使用C和D作为COMPANY和DEPARTMENT表的别名-
testdb=# SELECT C.ID, C.NAME, C.AGE, D.DEPT FROM COMPANY AS C, DEPARTMENT AS D WHERE C.ID=D.EMP_ID;
上面给出的PostgreSQL语句将产生以下输出-
链接:https://www.learnfk.comhttps://www.learnfk.com/postgresql/postgresql-alias-syntax.html
来源:LearnFk无涯教程网
id | name | age | dept ----+-------+-----+------------ 1 | Paul | 32 | IT Billing 2 | Learnfk | 25 | Engineering 7 | James | 24 | Finance 3 | Teddy | 23 | Engineering 4 | Mark | 25 | Finance 5 | David | 27 | Engineering 6 | Kim | 22 | Finance (7 rows)
让无涯教程看一个使用 COLUMN ALIAS 的示例,其中COMPANY_ID是ID列的别名,而COMPANY_NAME是名称列的别名-
testdb=# SELECT C.ID AS COMPANY_ID, C.NAME AS COMPANY_NAME, C.AGE, D.DEPT FROM COMPANY AS C, DEPARTMENT AS D WHERE C.ID=D.EMP_ID;
上面给出的PostgreSQL语句将产生以下输出-
链接:https://www.learnfk.comhttps://www.learnfk.com/postgresql/postgresql-alias-syntax.html
来源:LearnFk无涯教程网
company_id | company_name | age | dept ------------+--------------+-----+------------ 1 | Paul | 32 | IT Billing 2 | Learnfk | 25 | Engineering 7 | James | 24 | Finance 3 | Teddy | 23 | Engineering 4 | Mark | 25 | Finance 5 | David | 27 | Engineering 6 | Kim | 22 | Finance (7 rows)
祝学习愉快!(内容编辑有误?请选中要编辑内容 -> 右键 -> 修改 -> 提交!)