where语句
where语句可以进行内容的选择。
where语句需要加在from的后面。
SELECT employee_id, last_name, job_id, department_id
FROM employees
WHERE department_id = 90 ;
输出如下：
EMPLOYEE_ID LAST_NAME JOB_ID DEPARTMENT_ID
----------- -------------------------------------------------- -------------------- -------------
100 King AD_PRES 90
101 Kochhar AD_VP 90
102 De Haan AD_VP 90
查询日期或字符串
在查询字符串或者日期的时候，关键字应当用单引号框选
SELECT last_name, job_id, department_id
FROM employees
WHERE last_name = 'Whalen';
输出如下：
LAST_NAME JOB_ID DEPARTMENT_ID
-------------------------------------------------- -------------------- -------------
Whalen AD_ASST 10
比较符号查找
WHERE语句支持用数学符号进行条件限定
SELECT last_name, salary
FROM employees
WHERE salary <= 3000;
输出如下：
LAST_NAME SALARY
-------------------------------------------------- ----------
Baida 2900
Tobias 2800
Himuro 2600
Colmenares 2500
Mikkilineni 2700
Landry 2400
Markle 2200
Atkinson 2800
Marlow 2500
Olson 2100
Rogers 2900
Gee 2400
Philtanker 2200
Seo 2700
Patel 2500
Matos 2600
Vargas 2500
Sullivan 2500
Geoni 2800
Cabrio 3000
Gates 2900
Perkins 2500
Jones 2800
Feeney 3000
OConnell 2600
Grant 2600
已选择26行。
给定范围查找
WHERE支持范围限定
SELECT last_name, salary
FROM employees
WHERE salary BETWEEN 2500 AND 3500;
输出如下
LAST_NAME SALARY
-------------------------------------------------- ----------
Khoo 3100
Baida 2900
Tobias 2800
Himuro 2600
Colmenares 2500
Nayer 3200
Mikkilineni 2700
Bissot 3300
Atkinson 2800
Marlow 2500
Mallin 3300
Rogers 2900
Stiles 3200
Seo 2700
Patel 2500
Rajs 3500
Davies 3100
Matos 2600
Vargas 2500
Taylor 3200
Fleaur 3100
Sullivan 2500
Geoni 2800
Dellinger 3400
Cabrio 3000
Gates 2900
Perkins 2500
McCain 3200
Jones 2800
Walsh 3100
Feeney 3000
OConnell 2600
Grant 2600
已选择33行。
IN成员
我们可以用in成员对需要查询的成员进行限定
SELECT employee_id, last_name, salary, manager_id
FROM employees
WHERE manager_id IN (100, 101, 201);
输出如下
EMPLOYEE_ID LAST_NAME SALARY MANAGER_ID
----------- -------------------------------------------------- ---------- ----------
101 Kochhar 17000 100
102 De Haan 17000 100
108 Greenberg 12000 101
114 Raphaely 11000 100
120 Weiss 8000 100
121 Fripp 8200 100
122 Kaufling 7900 100
123 Vollman 6500 100
124 Mourgos 5800 100
145 Russell 14000 100
146 Partners 13500 100
147 Errazuriz 12000 100
148 Cambrault 11000 100
149 Zlotkey 10500 100
200 Whalen 4400 101
201 Hartstein 13000 100
202 Fay 6000 201
203 Mavris 6500 101
204 Baer 10000 101
205 Higgins 12000 101
已选择20行。
带%的模糊查询
我们可以用LIKE加上通配符%进行字符串模糊查询
其中%表示可以匹配任意多个字符
SELECT first_name
FROM employees
WHERE first_name LIKE 'S%';
输出如下
FIRST_NAME
----------------------------------------
Sundar
Shelli
Sarah
Shelley
Steven
Sundita
Steven
Susan
Samuel
Sarath
Stephen
Sigal
Shanta
已选择13行。
带_的模糊查询
我们可以用LIKE加单字符匹配符\(\_\)进行模糊查询，它代表任意一个字符（注意空格也算一个字符，但不能没有字符）
SELECT last_name
FROM employees
WHERE last_name LIKE '_o%';
输出如下：
LAST_NAME
--------------------------------------------------
Colmenares
Doran
Fox
Johnson
Jones
Kochhar
Lorentz
Mourgos
Popp
Rogers
Tobias
Vollman
已选择12行。
空值查询
我们可以用IS NULL语句来寻找空值
SELECT last_name, manager_id
FROM employees
WHERE manager_id IS NULL;
输出如下
LAST_NAME MANAGER_ID
-------------------------------------------------- ----------
King
逻辑运算符
WHERE语句中，如果要添加多个限制条件怎么办？
我们可以用带逻辑运算符的表达式解决这个问题
AND运算
SELECT employee_id, last_name, job_id, salary
FROM employees
WHERE salary >=10000
AND job_id LIKE '%MAN%';
输出如下
EMPLOYEE_ID LAST_NAME JOB_ID SALARY
----------- -------------------------------------------------- -------------------- ----------
114 Raphaely PU_MAN 11000
145 Russell SA_MAN 14000
146 Partners SA_MAN 13500
147 Errazuriz SA_MAN 12000
148 Cambrault SA_MAN 11000
149 Zlotkey SA_MAN 10500
201 Hartstein MK_MAN 13000
已选择7行。
OR运算
SELECT employee_id, last_name, job_id, salary
FROM employees
WHERE salary >= 10000
OR job_id LIKE '%MAN%';
输出如下
EMPLOYEE_ID LAST_NAME JOB_ID SALARY
----------- -------------------------------------------------- -------------------- ----------
100 King AD_PRES 24000
101 Kochhar AD_VP 17000
102 De Haan AD_VP 17000
108 Greenberg FI_MGR 12000
114 Raphaely PU_MAN 11000
120 Weiss ST_MAN 8000
121 Fripp ST_MAN 8200
122 Kaufling ST_MAN 7900
123 Vollman ST_MAN 6500
124 Mourgos ST_MAN 5800
145 Russell SA_MAN 14000
146 Partners SA_MAN 13500
147 Errazuriz SA_MAN 12000
148 Cambrault SA_MAN 11000
149 Zlotkey SA_MAN 10500
150 Tucker SA_REP 10000
156 King SA_REP 10000
162 Vishney SA_REP 10500
168 Ozer SA_REP 11500
169 Bloom SA_REP 10000
174 Abel SA_REP 11000
201 Hartstein MK_MAN 13000
204 Baer PR_REP 10000
205 Higgins AC_MGR 12000
已选择24行。
NOT运算
SELECT last_name, job_id
FROM employees
WHERE job_id
NOT IN ('IT_PROG', 'ST_CLERK', 'SA_REP');
输出如下：
LAST_NAME JOB_ID
-------------------------------------------------- --------------------
King AD_PRES
Kochhar AD_VP
De Haan AD_VP
Greenberg FI_MGR
Faviet FI_ACCOUNT
Chen FI_ACCOUNT
Sciarra FI_ACCOUNT
Urman FI_ACCOUNT
Popp FI_ACCOUNT
Raphaely PU_MAN
Khoo PU_CLERK
Baida PU_CLERK
Tobias PU_CLERK
Himuro PU_CLERK
Colmenares PU_CLERK
Weiss ST_MAN
Fripp ST_MAN
Kaufling ST_MAN
Vollman ST_MAN
Mourgos ST_MAN
Russell SA_MAN
Partners SA_MAN
Errazuriz SA_MAN
Cambrault SA_MAN
Zlotkey SA_MAN
Taylor SH_CLERK
Fleaur SH_CLERK
Sullivan SH_CLERK
Geoni SH_CLERK
Sarchand SH_CLERK
Bull SH_CLERK
Dellinger SH_CLERK
Cabrio SH_CLERK
Chung SH_CLERK
Dilly SH_CLERK
Gates SH_CLERK
Perkins SH_CLERK
Bell SH_CLERK
Everett SH_CLERK
McCain SH_CLERK
Jones SH_CLERK
Walsh SH_CLERK
Feeney SH_CLERK
OConnell SH_CLERK
Grant SH_CLERK
Whalen AD_ASST
Hartstein MK_MAN
Fay MK_REP
Mavris HR_REP
Baer PR_REP
Higgins AC_MGR
Gietz AC_ACCOUNT
已选择52行。
运算符优先级
在SQL中，运算符优先级如下所示，数字越小优先级越高
| 优先级 | 运算符 |
|---|---|
| 1 | 算数运算符 |
| 2 | 连接符 |
| 3 | 比较运算符 |
| 4 | IS [NOT] NULL, LIKE, [NOT] IN |
| 5 | [NOT] BETWEEN |
| 6 | 逻辑运算符NOT |
| 7 | 逻辑运算符AND |
| 8 | 逻辑运算符OR |
注意：我们可以添加括号以改变运算顺序
在下方这个指令中，AND前后的指令会先进行计算，然后再将所得结果与OR合并计算
SELECT last_name, job_id, salary
FROM employees
WHERE job_id = 'SA_REP'
OR job_id = 'AD_PRES'
AND salary > 15000;
输出如下：
LAST_NAME JOB_ID SALARY
-------------------------------------------------- -------------------- ----------
King AD_PRES 24000
Tucker SA_REP 10000
Bernstein SA_REP 9500
Hall SA_REP 9000
Olsen SA_REP 8000
Cambrault SA_REP 7500
Tuvault SA_REP 7000
King SA_REP 10000
Sully SA_REP 9500
McEwen SA_REP 9000
Smith SA_REP 8000
Doran SA_REP 7500
Sewall SA_REP 7000
Vishney SA_REP 10500
Greene SA_REP 9500
Marvins SA_REP 7200
Lee SA_REP 6800
Ande SA_REP 6400
Banda SA_REP 6200
Ozer SA_REP 11500
Bloom SA_REP 10000
Fox SA_REP 9600
Smith SA_REP 7400
Bates SA_REP 7300
Kumar SA_REP 6100
Abel SA_REP 11000
Hutton SA_REP 8800
Taylor SA_REP 8600
Livingston SA_REP 8400
Grant SA_REP 7000
Johnson SA_REP 6200
已选择31行。
如下方指令所示，我们用括号使得OR先完成计算，再进行AND计算
SELECT last_name, job_id, salary
FROM employees
WHERE (job_id = 'SA_REP'
OR job_id = 'AD_PRES')
AND salary > 15000;
输出如下
LAST_NAME JOB_ID SALARY
-------------------------------------------------- -------------------- ----------
King AD_PRES 24000
ORDER语句
我们可以用ORDER语句对输出的行进行排序
默认情况下，ORDER语句为从小到大排序
SELECT last_name, job_id, department_id, hire_date
FROM employees
ORDER BY hire_date ;
输出如下：
LAST_NAME JOB_ID DEPARTMENT_ID HIRE_DATE
-------------------------------------------------- -------------------- ------------- --------------
King AD_PRES 90 17-6月 -87
Whalen AD_ASST 10 17-9月 -87
Kochhar AD_VP 90 21-9月 -89
Hunold IT_PROG 60 03-1月 -90
Ernst IT_PROG 60 21-5月 -91
De Haan AD_VP 90 13-1月 -93
Mavris HR_REP 40 07-6月 -94
Baer PR_REP 70 07-6月 -94
Higgins AC_MGR 110 07-6月 -94
Gietz AC_ACCOUNT 110 07-6月 -94
Faviet FI_ACCOUNT 100 16-8月 -94
Greenberg FI_MGR 100 17-8月 -94
Raphaely PU_MAN 30 07-12月-94
Kaufling ST_MAN 50 01-5月 -95
Khoo PU_CLERK 30 18-5月 -95
Ladwig ST_CLERK 50 14-7月 -95
Rajs ST_CLERK 50 17-10月-95
Sarchand SH_CLERK 50 27-1月 -96
King SA_REP 80 30-1月 -96
Bell SH_CLERK 50 04-2月 -96
Hartstein MK_MAN 20 17-2月 -96
Sully SA_REP 80 04-3月 -96
Abel SA_REP 80 11-5月 -96
Mallin ST_CLERK 50 14-6月 -96
Weiss ST_MAN 50 18-7月 -96
McEwen SA_REP 80 01-8月 -96
Russell SA_MAN 80 01-10月-96
Partners SA_MAN 80 05-1月 -97
Davies ST_CLERK 50 29-1月 -97
Tucker SA_REP 80 30-1月 -97
Marlow ST_CLERK 50 16-2月 -97
Bull SH_CLERK 50 20-2月 -97
Everett SH_CLERK 50 03-3月 -97
Smith SA_REP 80 10-3月 -97
Errazuriz SA_MAN 80 10-3月 -97
Ozer SA_REP 80 11-3月 -97
Hutton SA_REP 80 19-3月 -97
Bernstein SA_REP 80 24-3月 -97
Fripp ST_MAN 50 10-4月 -97
Chung SH_CLERK 50 14-6月 -97
Austin IT_PROG 60 25-6月 -97
Nayer ST_CLERK 50 16-7月 -97
Tobias PU_CLERK 30 24-7月 -97
Dilly SH_CLERK 50 13-8月 -97
Fay MK_REP 20 17-8月 -97
Bissot ST_CLERK 50 20-8月 -97
Hall SA_REP 80 20-8月 -97
Chen FI_ACCOUNT 100 28-9月 -97
Sciarra FI_ACCOUNT 100 30-9月 -97
Vollman ST_MAN 50 10-10月-97
Stiles ST_CLERK 50 26-10月-97
Atkinson ST_CLERK 50 30-10月-97
Vishney SA_REP 80 11-11月-97
Doran SA_REP 80 15-12月-97
Baida PU_CLERK 30 24-12月-97
Fox SA_REP 80 24-1月 -98
Taylor SH_CLERK 50 24-1月 -98
Pataballa IT_PROG 60 05-2月 -98
Seo ST_CLERK 50 12-2月 -98
Fleaur SH_CLERK 50 23-2月 -98
Urman FI_ACCOUNT 100 07-3月 -98
Matos ST_CLERK 50 15-3月 -98
Bloom SA_REP 80 23-3月 -98
Taylor SA_REP 80 24-3月 -98
Olsen SA_REP 80 30-3月 -98
Patel ST_CLERK 50 06-4月 -98
Livingston SA_REP 80 23-4月 -98
Walsh SH_CLERK 50 24-4月 -98
Feeney SH_CLERK 50 23-5月 -98
Dellinger SH_CLERK 50 24-6月 -98
McCain SH_CLERK 50 01-7月 -98
Vargas ST_CLERK 50 09-7月 -98
Gates SH_CLERK 50 11-7月 -98
Rogers ST_CLERK 50 26-8月 -98
Mikkilineni ST_CLERK 50 28-9月 -98
Sewall SA_REP 80 03-11月-98
Himuro PU_CLERK 30 15-11月-98
Cambrault SA_REP 80 09-12月-98
Landry ST_CLERK 50 14-1月 -99
Cabrio SH_CLERK 50 07-2月 -99
Lorentz IT_PROG 60 07-2月 -99
Smith SA_REP 80 23-2月 -99
Jones SH_CLERK 50 17-3月 -99
Greene SA_REP 80 19-3月 -99
Bates SA_REP 80 24-3月 -99
Olson ST_CLERK 50 10-4月 -99
Grant SA_REP 24-5月 -99
OConnell SH_CLERK 50 21-6月 -99
Sullivan SH_CLERK 50 21-6月 -99
Colmenares PU_CLERK 30 10-8月 -99
Cambrault SA_MAN 80 15-10月-99
Mourgos ST_MAN 50 16-11月-99
Tuvault SA_REP 80 23-11月-99
Popp FI_ACCOUNT 100 07-12月-99
Gee ST_CLERK 50 12-12月-99
Perkins SH_CLERK 50 19-12月-99
Johnson SA_REP 80 04-1月 -00
Grant SH_CLERK 50 13-1月 -00
Marvins SA_REP 80 24-1月 -00
Zlotkey SA_MAN 80 29-1月 -00
Geoni SH_CLERK 50 03-2月 -00
Philtanker ST_CLERK 50 06-2月 -00
Lee SA_REP 80 23-2月 -00
Markle ST_CLERK 50 08-3月 -00
Ande SA_REP 80 24-3月 -00
Banda SA_REP 80 21-4月 -00
Kumar SA_REP 80 21-4月 -00
已选择107行。
DESC倒序输出
我们可以添加DESC让数据倒序输出
SELECT last_name, job_id, department_id, hire_date
FROM employees
ORDER BY hire_date DESC ;
输出如下：
LAST_NAME JOB_ID DEPARTMENT_ID HIRE_DATE
-------------------------------------------------- -------------------- ------------- --------------
Kumar SA_REP 80 21-4月 -00
Banda SA_REP 80 21-4月 -00
Ande SA_REP 80 24-3月 -00
Markle ST_CLERK 50 08-3月 -00
Lee SA_REP 80 23-2月 -00
Philtanker ST_CLERK 50 06-2月 -00
Geoni SH_CLERK 50 03-2月 -00
Zlotkey SA_MAN 80 29-1月 -00
Marvins SA_REP 80 24-1月 -00
Grant SH_CLERK 50 13-1月 -00
Johnson SA_REP 80 04-1月 -00
Perkins SH_CLERK 50 19-12月-99
Gee ST_CLERK 50 12-12月-99
Popp FI_ACCOUNT 100 07-12月-99
Tuvault SA_REP 80 23-11月-99
Mourgos ST_MAN 50 16-11月-99
Cambrault SA_MAN 80 15-10月-99
Colmenares PU_CLERK 30 10-8月 -99
Sullivan SH_CLERK 50 21-6月 -99
OConnell SH_CLERK 50 21-6月 -99
Grant SA_REP 24-5月 -99
Olson ST_CLERK 50 10-4月 -99
Bates SA_REP 80 24-3月 -99
Greene SA_REP 80 19-3月 -99
Jones SH_CLERK 50 17-3月 -99
Smith SA_REP 80 23-2月 -99
Cabrio SH_CLERK 50 07-2月 -99
Lorentz IT_PROG 60 07-2月 -99
Landry ST_CLERK 50 14-1月 -99
Cambrault SA_REP 80 09-12月-98
Himuro PU_CLERK 30 15-11月-98
Sewall SA_REP 80 03-11月-98
Mikkilineni ST_CLERK 50 28-9月 -98
Rogers ST_CLERK 50 26-8月 -98
Gates SH_CLERK 50 11-7月 -98
Vargas ST_CLERK 50 09-7月 -98
McCain SH_CLERK 50 01-7月 -98
Dellinger SH_CLERK 50 24-6月 -98
Feeney SH_CLERK 50 23-5月 -98
Walsh SH_CLERK 50 24-4月 -98
Livingston SA_REP 80 23-4月 -98
Patel ST_CLERK 50 06-4月 -98
Olsen SA_REP 80 30-3月 -98
Taylor SA_REP 80 24-3月 -98
Bloom SA_REP 80 23-3月 -98
Matos ST_CLERK 50 15-3月 -98
Urman FI_ACCOUNT 100 07-3月 -98
Fleaur SH_CLERK 50 23-2月 -98
Seo ST_CLERK 50 12-2月 -98
Pataballa IT_PROG 60 05-2月 -98
Taylor SH_CLERK 50 24-1月 -98
Fox SA_REP 80 24-1月 -98
Baida PU_CLERK 30 24-12月-97
Doran SA_REP 80 15-12月-97
Vishney SA_REP 80 11-11月-97
Atkinson ST_CLERK 50 30-10月-97
Stiles ST_CLERK 50 26-10月-97
Vollman ST_MAN 50 10-10月-97
Sciarra FI_ACCOUNT 100 30-9月 -97
Chen FI_ACCOUNT 100 28-9月 -97
Hall SA_REP 80 20-8月 -97
Bissot ST_CLERK 50 20-8月 -97
Fay MK_REP 20 17-8月 -97
Dilly SH_CLERK 50 13-8月 -97
Tobias PU_CLERK 30 24-7月 -97
Nayer ST_CLERK 50 16-7月 -97
Austin IT_PROG 60 25-6月 -97
Chung SH_CLERK 50 14-6月 -97
Fripp ST_MAN 50 10-4月 -97
Bernstein SA_REP 80 24-3月 -97
Hutton SA_REP 80 19-3月 -97
Ozer SA_REP 80 11-3月 -97
Smith SA_REP 80 10-3月 -97
Errazuriz SA_MAN 80 10-3月 -97
Everett SH_CLERK 50 03-3月 -97
Bull SH_CLERK 50 20-2月 -97
Marlow ST_CLERK 50 16-2月 -97
Tucker SA_REP 80 30-1月 -97
Davies ST_CLERK 50 29-1月 -97
Partners SA_MAN 80 05-1月 -97
Russell SA_MAN 80 01-10月-96
McEwen SA_REP 80 01-8月 -96
Weiss ST_MAN 50 18-7月 -96
Mallin ST_CLERK 50 14-6月 -96
Abel SA_REP 80 11-5月 -96
Sully SA_REP 80 04-3月 -96
Hartstein MK_MAN 20 17-2月 -96
Bell SH_CLERK 50 04-2月 -96
King SA_REP 80 30-1月 -96
Sarchand SH_CLERK 50 27-1月 -96
Rajs ST_CLERK 50 17-10月-95
Ladwig ST_CLERK 50 14-7月 -95
Khoo PU_CLERK 30 18-5月 -95
Kaufling ST_MAN 50 01-5月 -95
Raphaely PU_MAN 30 07-12月-94
Greenberg FI_MGR 100 17-8月 -94
Faviet FI_ACCOUNT 100 16-8月 -94
Mavris HR_REP 40 07-6月 -94
Baer PR_REP 70 07-6月 -94
Higgins AC_MGR 110 07-6月 -94
Gietz AC_ACCOUNT 110 07-6月 -94
De Haan AD_VP 90 13-1月 -93
Ernst IT_PROG 60 21-5月 -91
Hunold IT_PROG 60 03-1月 -90
Kochhar AD_VP 90 21-9月 -89
Whalen AD_ASST 10 17-9月 -87
King AD_PRES 90 17-6月 -87
已选择107行。
对化名排序
我们可以基于运算出的数据进行排序
SELECT employee_id, last_name, salary*12 annsal
FROM employees
ORDER BY annsal;
输出如下
EMPLOYEE_ID LAST_NAME ANNSAL
----------- -------------------------------------------------- ----------
132 Olson 25200
128 Markle 26400
136 Philtanker 26400
135 Gee 28800
127 Landry 28800
119 Colmenares 30000
131 Marlow 30000
140 Patel 30000
144 Vargas 30000
182 Sullivan 30000
191 Perkins 30000
143 Matos 31200
199 Grant 31200
118 Himuro 31200
198 OConnell 31200
139 Seo 32400
126 Mikkilineni 32400
130 Atkinson 33600
183 Geoni 33600
117 Tobias 33600
195 Jones 33600
134 Rogers 34800
116 Baida 34800
190 Gates 34800
197 Feeney 36000
187 Cabrio 36000
181 Fleaur 37200
115 Khoo 37200
142 Davies 37200
196 Walsh 37200
194 McCain 38400
125 Nayer 38400
138 Stiles 38400
180 Taylor 38400
133 Mallin 39600
129 Bissot 39600
186 Dellinger 40800
141 Rajs 42000
189 Dilly 43200
137 Ladwig 43200
188 Chung 45600
193 Everett 46800
192 Bell 48000
185 Bull 49200
107 Lorentz 50400
184 Sarchand 50400
200 Whalen 52800
106 Pataballa 57600
105 Austin 57600
124 Mourgos 69600
104 Ernst 72000
202 Fay 72000
173 Kumar 73200
167 Banda 74400
179 Johnson 74400
166 Ande 76800
123 Vollman 78000
203 Mavris 78000
165 Lee 81600
113 Popp 82800
155 Tuvault 84000
161 Sewall 84000
178 Grant 84000
164 Marvins 86400
172 Bates 87600
171 Smith 88800
154 Cambrault 90000
160 Doran 90000
111 Sciarra 92400
112 Urman 93600
122 Kaufling 94800
159 Smith 96000
120 Weiss 96000
153 Olsen 96000
110 Chen 98400
121 Fripp 98400
206 Gietz 99600
177 Livingston 100800
176 Taylor 103200
175 Hutton 105600
103 Hunold 108000
109 Faviet 108000
152 Hall 108000
158 McEwen 108000
157 Sully 114000
163 Greene 114000
151 Bernstein 114000
170 Fox 115200
204 Baer 120000
169 Bloom 120000
156 King 120000
150 Tucker 120000
162 Vishney 126000
149 Zlotkey 126000
148 Cambrault 132000
114 Raphaely 132000
174 Abel 132000
168 Ozer 138000
205 Higgins 144000
108 Greenberg 144000
147 Errazuriz 144000
201 Hartstein 156000
146 Partners 162000
145 Russell 168000
102 De Haan 204000
101 Kochhar 204000
100 King 288000
已选择107行。
多关键字排序
在排序时，我们可以给排序添加多个关键字
排序规则：先比较第一关键字，如第一关键字不同则按第一关键字进行，否则比较下一个关键字
SELECT last_name, department_id, salary
FROM employees
ORDER BY department_id, salary DESC;
输出如下：
LAST_NAME DEPARTMENT_ID SALARY
-------------------------------------------------- ------------- ----------
Whalen 10 4400
Hartstein 20 13000
Fay 20 6000
Raphaely 30 11000
Khoo 30 3100
Baida 30 2900
Tobias 30 2800
Himuro 30 2600
Colmenares 30 2500
Mavris 40 6500
Fripp 50 8200
Weiss 50 8000
Kaufling 50 7900
Vollman 50 6500
Mourgos 50 5800
Sarchand 50 4200
Bull 50 4100
Bell 50 4000
Everett 50 3900
Chung 50 3800
Dilly 50 3600
Ladwig 50 3600
Rajs 50 3500
Dellinger 50 3400
Mallin 50 3300
Bissot 50 3300
Taylor 50 3200
Nayer 50 3200
Stiles 50 3200
McCain 50 3200
Davies 50 3100
Walsh 50 3100
Fleaur 50 3100
Cabrio 50 3000
Feeney 50 3000
Rogers 50 2900
Gates 50 2900
Atkinson 50 2800
Jones 50 2800
Geoni 50 2800
Mikkilineni 50 2700
Seo 50 2700
Matos 50 2600
OConnell 50 2600
Grant 50 2600
Perkins 50 2500
Marlow 50 2500
Sullivan 50 2500
Patel 50 2500
Vargas 50 2500
Gee 50 2400
Landry 50 2400
Markle 50 2200
Philtanker 50 2200
Olson 50 2100
Hunold 60 9000
Ernst 60 6000
Austin 60 4800
Pataballa 60 4800
Lorentz 60 4200
Baer 70 10000
Russell 80 14000
Partners 80 13500
Errazuriz 80 12000
Ozer 80 11500
Abel 80 11000
Cambrault 80 11000
Zlotkey 80 10500
Vishney 80 10500
Bloom 80 10000
Tucker 80 10000
King 80 10000
Fox 80 9600
Bernstein 80 9500
Sully 80 9500
Greene 80 9500
Hall 80 9000
McEwen 80 9000
Hutton 80 8800
Taylor 80 8600
Livingston 80 8400
Olsen 80 8000
Smith 80 8000
Cambrault 80 7500
Doran 80 7500
Smith 80 7400
Bates 80 7300
Marvins 80 7200
Tuvault 80 7000
Sewall 80 7000
Lee 80 6800
Ande 80 6400
Johnson 80 6200
Banda 80 6200
Kumar 80 6100
King 90 24000
Kochhar 90 17000
De Haan 90 17000
Greenberg 100 12000
Faviet 100 9000
Chen 100 8200
Urman 100 7800
Sciarra 100 7700
Popp 100 6900
Higgins 110 12000
Gietz 110 8300
Grant 7000
已选择107行。