Oracle中查询数据的倒序排列(oracle中倒叙)
Oracle中查询数据的倒序排列
Oracle是一种非常流行的数据库管理系统,而数据库的读取和排序是很常见的操作。倒序排列就是将数据从小到大的顺序,变为从大到小的顺序。在Oracle中,我们可以使用ORDER BY DESC关键字实现数据倒序排列。
以下是一些代码示例:
我们需要创建一个包含一些数据的表:
“`SQL
CREATE TABLE employees (
employee_id NUMBER(4) PRIMARY KEY,
first_name VARCHAR2(20),
last_name VARCHAR2(25),
eml VARCHAR2(25),
phone_number VARCHAR2(20),
hire_date DATE,
job_id VARCHAR2(10),
salary NUMBER(8,2),
commission_pct NUMBER(2,2),
manager_id NUMBER(4),
department_id NUMBER(2)
);
INSERT INTO employees VALUES (1, ‘John’, ‘Doe’, ‘john.doe@example.com’, ‘555.555.5555’, ’01-JAN-2000′, ‘IT_PROG’, 5000, NULL, NULL, 60);
INSERT INTO employees VALUES (2, ‘Jane’, ‘Doe’, ‘jane.doe@example.com’, ‘555.555.5556’, ’01-JAN-2001′, ‘HR_REP’, 6000, NULL, NULL, 60);
INSERT INTO employees VALUES (3, ‘Albert’, ‘Einstein’, ‘albert.einstein@example.com’, ‘555.555.5557’, ’01-JAN-2002′, ‘IT_PROG’, 7000, NULL, NULL, 60);
INSERT INTO employees VALUES (4, ‘Thomas’, ‘Edison’, ‘thomas.edison@example.com’, ‘555.555.5558’, ’01-JAN-2003′, ‘SA_REP’, 8000, NULL, NULL, 60);
INSERT INTO employees VALUES (5, ‘Galileo’, ‘Galilei’, ‘galileo.galilei@example.com’, ‘555.555.5559’, ’01-JAN-2004′, ‘IT_PROG’, 9000, NULL, NULL, 60);
接下来,我们可以使用ORDER BY DESC关键字来按照salary字段降序排列,即从高到低:
```SQLSELECT * FROM employees ORDER BY salary DESC;
输出结果将是:
EMPLOYEE_ID FIRST_NAME LAST_NAME EML PHONE_NUMBER HIRE_DATE JOB_ID SALARY COMMISSION_PCT MANAGER_ID DEPARTMENT_ID
----------- ----------- --------------- ------------------------- ------------ ----------- -------- ------ -------------- ---------- -------------5 Galileo Galilei galileo.galilei@example.com 555.555.5559 01-JAN-2004 IT_PROG 9000 (null) (null) 60
4 Thomas Edison thomas.edison@example.com 555.555.5558 01-JAN-2003 SA_REP 8000 (null) (null) 603 Albert Einstein albert.einstein@example... 555.555.5557 01-JAN-2002 IT_PROG 7000 (null) (null) 60
2 Jane Doe jane.doe@example.com 555.555.5556 01-JAN-2001 HR_REP 6000 (null) (null) 601 John Doe john.doe@example.com 555.555.5555 01-JAN-2000 IT_PROG 5000 (null) (null) 60
我们还可以使用多列排序,例如按照salary字段降序、hire_date字段升序进行排序:
“`SQL
SELECT * FROM employees ORDER BY salary DESC, hire_date ASC;
输出结果将是:
EMPLOYEE_ID FIRST_NAME LAST_NAME EML PHONE_NUMBER HIRE_DATE JOB_ID SALARY COMMISSION_PCT MANAGER_ID DEPARTMENT_ID
———– ———– ————— ————————- ———— ———– ——– —— ————– ———- ————-
5 Galileo Galilei galileo.galilei@example.com 555.555.5559 01-JAN-2004 IT_PROG 9000 (null) (null) 60
4 Thomas Edison thomas.edison@example.com 555.555.5558 01-JAN-2003 SA_REP 8000 (null) (null) 60
3 Albert Einstein albert.einstein@example… 555.555.5557 01-JAN-2002 IT_PROG 7000 (null) (null) 60
2 Jane Doe jane.doe@example.com 555.555.5556 01-JAN-2001 HR_REP 6000 (null) (null) 60
1 John Doe john.doe@example.com 555.555.5555 01-JAN-2000 IT_PROG 5000 (null) (null) 60
ORDER BY DESC是一种非常实用的查询语句。我们可以通过Oracle中的ORDER BY DESC命令将结果按指定顺序排列,实现更加精准高效的数据查询操作。