Select命令用于从一个或多个表中获取记录数据。
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;
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-
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+----+----------+-----+-----------+----------+ | 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 | +----+----------+-----+-----------+----------+
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