Select命令用于从一个或多个表中获取记录数据。
Select - 语法
SELECT语句的基本语法如下-
SELECT [ TOP term ] [ DISTINCT | ALL ] selectExpression [,...] FROM tableExpression [,...] [ WHERE expression ] [ GROUP BY expression [,...] ] [ HAVING expression ] [ { UNION [ ALL ] | MINUS | EXCEPT | INTERSECT } select ] [ ORDER BY order [,...] ] [ [ LIMIT expression ] [ OFFSET expression ] [ SAMPLE_SIZE rowCountInt ] ] [ FOR UPDATE ]
要获取所有可用字段，请使用以下语法。
SELECT * FROM table_name;
Select - 示例
考虑具有以下记录的CUSTOMER表-
+----+----------+-----+-----------+----------+ | ID | NAME | AGE | ADDRESS | SALARY | +----+----------+-----+-----------+----------+ | 1 | Ramesh | 32 | Ahmedabad | 2000.00 | | 2 | Khilan | 25 | Delhi | 1500.00 | | 3 | kaushik | 23 | Kota | 2000.00 | | 4 | Chaitali | 25 | Mumbai | 6500.00 | | 5 | Hardik | 27 | Bhopal | 8500.00 | | 6 | Komal | 22 | MP | 4500.00 | | 7 | Learnfk | 24 | Indore | 10000.00 | +----+----------+-----+-----------+----------+
要获取客户表以及给定的数据，请执行以下查询。
CREATE TABLE CUSTOMER (id number, name varchar(20), age number, address varchar(20), salary number);INSERT into CUSTOMER values (1, Ramesh, 32, Ahmedabad, 2000); INSERT into CUSTOMER values (2, Khilan, 25, Delhi, 1500); INSERT into CUSTOMER values (3, kaushik, 23, Kota, 2000); INSERT into CUSTOMER values (4, Chaitali, 25, Mumbai, 6500); INSERT into CUSTOMER values (5, Hardik, 27, Bhopal, 8500); INSERT into CUSTOMER values (6, Komal, 22, MP, 4500); INSERT into CUSTOMER values (7, Learnfk, 24, Indore, 10000);
以下命令是一个示例，它将获取CUSTOMER表中可用的客户的ID，名称和薪水字段。
SELECT ID, NAME, SALARY FROM CUSTOMERS;
上面的命令产生以下输出。
+----+----------+----------+ | ID | NAME | SALARY | +----+----------+----------+ | 1 | Ramesh | 2000.00 | | 2 | Khilan | 1500.00 | | 3 | kaushik | 2000.00 | | 4 | Chaitali | 6500.00 | | 5 | Hardik | 8500.00 | | 6 | Komal | 4500.00 | | 7 | Learnfk | 10000.00 | +----+----------+----------+
使用以下查询来获取CUSTOMERS表的所有字段。
SQL> SELECT * FROM CUSTOMERS;
上面的查询产生以下输出-
+----+----------+-----+-----------+----------+ | ID | NAME | AGE | ADDRESS | SALARY | +----+----------+-----+-----------+----------+ | 1 | Ramesh | 32 | Ahmedabad | 2000.00 | | 2 | Khilan | 25 | Delhi | 1500.00 | | 3 | kaushik | 23 | Kota | 2000.00 | | 4 | Chaitali | 25 | Mumbai | 6500.00 | | 5 | Hardik | 27 | Bhopal | 8500.00 | | 6 | Komal | 22 | MP | 4500.00 | | 7 | Learnfk | 24 | Indore | 10000.00 | +----+----------+-----+-----------+----------+
