常用SQL语句2（Oracle）

  1 /********************************SCOTT Database*******************************/
  2 select * from EMP;
  3 select * from DEPT;
  4 select * from SALGRADE;
  5 
  6 select ename, sal*12 from emp;
  7 
  8 /*system empty table*/
  9 select * from dual;
 10 select 2*3 from dual;
 11 
 12 select sysdate from dual;
 13 /*alias*/
 14 select ename, sal*12 annual_sal from emp;
 15 /*alias with space*/
 16 select ename, sal*12 "annual sal" from emp;
 17 
 18 /*0 not equal null value*/
 19 select ename, comm from emp;
 20 
 21 /*year salary + comm, any contains empty‘s math operation result is empty*/
 22 select ename, sal*12 + comm from emp;
 23 
 24 select ename||sal from emp;
 25 
 26 /*concat string*/
 27 select ename || ‘abcdefg‘ from emp;
 28 
 29 /*2 ‘ instead of 1 ‘*/
 30 select ename || ‘abcdefg‘‘abcd‘ from emp;
 31 
 32 select deptno from emp;
 33 
 34 /*remove duplicate*/
 35 select distinct deptno from emp;
 36 
 37 select distinct deptno, job from emp;
 38 
 39 select * from emp where deptno = 10;
 40 
 41 select * from EMP where ename = ‘CLARK‘;
 42 
 43 select ename, sal from emp where SAL > 1500; 
 44 
 45 select ename, sal from emp where deptno <> 10;
 46 
 47 select ename, sal from emp where ename > ‘CBA‘;
 48 
 49 select ename, sal from emp where sal between 800 and 1500;
 50 
 51 select ename, sal from emp where sal >= 800 and sal <= 1500;
 52 
 53 /*empty value*/
 54 select ename, sal, comm from emp where comm = null;
 55 
 56 select ename, sal, comm from emp where comm is null;
 57 
 58 select ename, sal, comm from emp where comm is not null;
 59 
 60 select ename, sal, comm from emp where sal in (800, 1500, 2000);
 61 
 62 select ename, sal, comm from emp where ename in (‘SMITH‘, ‘KING‘, ‘ABC‘);
 63 
 64 select ename, sal from emp where DEPTNO = 10 and sal > 1000;
 65 
 66 select ename, sal from emp where DEPTNO = 10 or sal > 1000; 
 67 
 68 select ename, sal from emp where DEPTNO = 10 and sal not in (800, 1500);
 69 
 70 /*% means 0 or more*/
 71 select ename from emp where ENAME like ‘%ALL%‘;
 72 
 73 select ename from emp where ename like ‘_A%‘;
 74 
 75 /*contains % in the selected rows need escape sequence*/
 76 
 77 select ename from emp where ENAME like ‘%\%%‘;
 78 
 79 /*default escapse sequence is \ but we can defintion by use <escape> ‘$‘ */
 80 select ename from emp where ename like ‘%$%%‘ escape ‘$‘;
 81 
 82 select * from DEPT;
 83 
 84 /*order by asc desc defalut is asc*/
 85 select * from DEPT order by DEPTNO desc;
 86 
 87 select empno, ename from emp;
 88 
 89 select empno, ename from emp order by EMPNO asc;
 90 
 91 select empno, ename from emp order by EMPNO desc;
 92 
 93 select empno, ename from emp where deptno <> 10 order by empno asc;
 94 
 95 select ename, sal, deptno from emp order by deptno asc; 
 96 
 97 select ename, sal, deptno from emp order by deptno asc, ename desc;
 98 
 99 select ename, sal*12 annual_sal from emp where ename not like ‘_A%‘ and sal > 800 order by sal desc; 
100 
101 select lower(ename) from emp
102 
103 select ename from emp where lower(ename) like ‘_a%‘;
104 
105 select ename from emp where ename like ‘_a%‘ or ename like ‘_A%‘;
106 
107 select substr(ename, 1, 3) from emp;
108 
109 select substr(ename, 2, 3) from emp;
110 
111 select chr(65) from dual;
112 
113 select ascii(‘A‘) from dual;
114 
115 select round(23.652) from dual;
116 
117 select round(23.652, 2) from dual;
118 
119 select round(23.652, -1) from dual;
120 
121 /* 9 means number, is this position has no number, it will not be displayed
122    ‘$99,999.9999‘ --> $800.0000
123    ‘$99,999.9999‘ --> $1,500.0000
124    ‘L99,999.9999‘ --> Y1,500.0000
125    ‘$00000.0000‘ --> $00800.0000
126    ‘$00000.0000‘ --> $01500.0000
127    
128    to_char
129 */
130 
131 select to_char(sal, ‘$99,999.9999‘) from emp;
132 
133 select to_char(sal, ‘$00000.0000‘) from emp;
134 
135 select hiredate from emp;
136 
137 /* Date format
138  YYYY -- year
139  MM   -- month
140  DD   -- day
141  HH   -- 12 hour
142  HH24 -- 24 hour
143  MI   -- minute
144  SS   -- second
145 */
146 select to_char(hiredate, ‘YYYY-MM-DD HH:MI:SS‘) joindate from emp;
147 
148 /*to_date*/
149 select ename, hiredate from emp where HIREDATE > to_date(‘1981-2-20 12:34:56‘, ‘YYYY-MM-DD HH24:MI:SS‘);
150 
151 /*to_number*/
152 select sal from EMP where sal > to_number(‘$1,250.00‘, ‘$9,999.99‘);
153 
154 select ename, sal*12 + comm from emp;
155 
156 
157 /* 
158    function nvl to deal with null value to math operation
159    if comm is null then o instead of null or it will be comm
160 */
161 select ename, sal*12 + nvl(comm, 0) from emp;
162 
163 
164 /*
165    group function : min, max, avg, count, sum   
166 */
167 select max(sal) maxsal from emp;
168 
169 select min(sal) minsal from emp;
170 
171 select avg(sal) avgsal from emp;
172 
173 select to_char(avg(sal),‘999999999.99‘) avgsal from emp;
174 
175 select round(avg(sal),2) avgsal from emp;
176 
177 select sum(sal) from emp;
178 
179 select count(*) records from emp;
180 
181 select count(*) from emp where deptno = 10;
182 
183 select count(ename) from emp;
184 
185 /*count the field which is not null*/
186 select count(comm) from emp;
187 
188 select count(deptno) from emp;
189  
190 select count(distinct deptno) from emp;
191 
192 /*
193     function : group by
194 */
195 
196 /* which department‘s avg salary is highest*/
197 select sal, deptno from emp;
198 
199 
200 /*department avg salary*/
201 select deptno, to_char(avg(sal),‘99999999.99‘) depavgsal from emp group by deptno;
202 
203 select deptno, job, max(sal) maxsal from emp group by deptno, job;
204 
205 /*the highest salary in the company*/
206 select max(sal) from emp;
207 
208 /*who is the highest salary in the company*/
209 select ename from emp where sal = (select max(sal) from emp);
210 
211 /*the highest salary in the department*/
212 select deptno, max(sal) from emp group by deptno;
213 
214 select to_char(avg(sal), ‘99999999.99‘) avgsal, deptno from emp group by deptno;
215 
216 /* having is limited with grouping*/
217 select to_char(avg(sal), ‘99999999.99‘) avgsal, deptno from emp group by deptno having avg(sal) > 2000;
218 
219 select deptno, max(sal) from emp where SAL > 1000 group by deptno having avg(sal) > 2000 order by deptno desc; 
220 
221 select deptno, to_char(avg(sal), ‘99999999.99‘) from emp where sal > 1200 group by deptno having avg(sal) > 1500 order by avg(sal) desc;
222 
223 
224 select ename, sal from emp where SAL = (select max(sal) from emp);
225 
226 select ename, sal from emp where sal > (select avg(sal) from emp);
227 
228 select ename, sal from emp join (select max(sal) maxsal, deptno from emp group by deptno) t on (emp.sal = t.maxsal and emp.deptno = t.deptno);
229 
230 select * from SALGRADE;
231 
232 select deptno, to_char(avg(sal), ‘999999999.99‘) s from emp group by deptno;
233 
234 SELECT dname,grade,to_char(S, ‘999999.999‘) FROM dept,(SELECT deptno,grade,s FROM (SELECT deptno,grade,s FROM (SELECT deptno,avg(sal) s FROM emp GROUP BY deptno),salgrade WHERE s BETWEEN losal AND hisal ORDER BY grade DESC) t WHERE ROWNUM=1) t WHERE dept.deptno=t.deptno;
235 
236 SELECT dname,grade,to_char(S, ‘999999.999‘) FROM dept,(SELECT deptno,grade,s FROM (SELECT deptno,grade,s FROM (SELECT deptno,avg(sal) s FROM emp GROUP BY deptno),salgrade WHERE s BETWEEN losal AND hisal ORDER BY grade DESC) t WHERE ROWNUM=1) t WHERE dept.deptno=t.deptno;
237 
238 
239 /*self table connection*/
240 
241 select empno, ename, mgr from emp;
242 
243 select e1.ename, e2.ename from emp e1, emp e2 where e1.MGR = e2.EMPNO;
244 
245 select ename, dname from EMP, DEPT where emp.DEPTNO = dept.DEPTNO;
246 
247 select ename, dname from EMP join DEPT on (emp.DEPTNO = dept.DEPTNO); 
248 
249 select ename, dname from EMP join DEPT using (deptno);
250 
251 select ename, grade from emp e join salgrade s on (e.SAL between s.LOSAL and s.HISAL);
252 
253 select ename, dname, grade from emp e join dept d on (e.DEPTNO = d.DEPTNO) join salgrade s on (e.SAL between s.LOSAL and s.HISAL) where ename not like ‘_A%‘;  
254 
255 /*left join == left outer join*/
256 select e1.ename, e2.ename from emp e1 left join emp e2 on (e1.mgr = e2.empno);
257 
258 select e1.ename, e2.ename from emp e1 left outer join emp e2 on (e1.mgr = e2.empno);
259 
260 select * from dept;
261 
262 select ename, dname from emp e right join DEPT d on (e.DEPTNO = d.DEPTNO);
263 
264 select ename, dname from emp e right outer join DEPT d on (e.DEPTNO = d.DEPTNO);
265 
266 /* full join */
267 select ename, dname from emp e full join DEPT d on (e.DEPTNO = d.DEPTNO);
268 
269 /*department avg salary*/
270 select deptno, to_char(avg(sal), ‘9999999.99‘) from emp group by deptno;
271 
272 /*department avg salary‘s grade*/
273 select deptno, avg_sal, grade 
274 from (select deptno, to_char(avg(sal), ‘999999.99‘) avg_sal from emp group by deptno) t 
275 join SALGRADE s 
276 on (t.avg_sal between s.LOSAL and s.HISAL);
277 
278 /*salary grade for every employee*/
279 select ename, deptno, grade from emp e join SALGRADE s on (e.SAL between s.LOSAL and s.HISAL);
280 
281 select deptno, to_char(avg(grade), ‘9.9‘) avg_grade
282 from (select ename, deptno, grade from emp e join SALGRADE s on (e.SAL between s.LOSAL and s.HISAL)) t
283 group by t.deptno;
284 
285 /* who is manager*/
286 select ename from emp where EMPNO in (select mgr from emp);
287 
288 select ename from emp where EMPNO in (select distinct mgr from emp);
289 
290 select * from emp;
291 
292 /*select highest salary*/
293 select max(sal) from emp;
294 
295 select distinct e1.sal from emp e1 join emp e2 on (e1.SAL < e2.SAL);
296 
297 /* please don‘t use group function to find the max salary*/
298 select distinct sal from emp where SAL not in (select distinct e1.sal from emp e1 join emp e2 on (e1.SAL < e2.SAL));
299 
300 select deptno, avg_sal from (select to_char(avg(sal), ‘99999.99‘) avg_sal, deptno from emp group by deptno) 
301 where avg_sal = (select max(avg_sal) from (select to_char(avg(sal),‘999999.99‘) avg_sal, deptno from emp group by deptno));
302 
303 
304 select max(avg_sal) from (select to_char(avg(sal),‘999999.99‘) avg_sal, deptno from emp group by deptno);
305 select to_char(avg(sal), ‘99999.99‘) avg_sal, deptno from emp group by deptno;
306 
307 
308 /*avg salary is highest*/
309 select deptno, avg_sal from (select to_char(avg(sal), ‘99999.99‘) avg_sal, deptno from emp group by deptno) where avg_sal = (select max(avg_sal) from (select to_char(avg(sal),‘99999.99‘) avg_sal, deptno from emp group by deptno));
310 
311 /*the depatname of the highest avg salary*/
312 select dname from dept where deptno = 
313 (select deptno from (select to_char(avg(sal), ‘99999.99‘) avg_sal, deptno from emp group by deptno) where avg_sal = (select max(avg_sal) from (select to_char(avg(sal),‘99999.99‘) avg_sal, deptno from emp group by deptno)));
314 
315 
316 select avg(sal) sal_avg from emp group by deptno;
317 
318 select deptno, avg(sal) sal_avg from emp group by deptno;
319 
320 select deptno, to_char(sal_avg, ‘999999.99‘) sal_avg, grade 
321 from (select deptno, avg(sal) sal_avg from emp group by deptno) t 
322 join salgrade s
323 on (t.sal_avg between s.LOSAL and s.HISAL);
324 
325 
326 select min(grade) from (
327     select deptno, to_char(sal_avg, ‘999999.99‘) sal_avg, grade 
328     from (select deptno, avg(sal) sal_avg from emp group by deptno) t 
329     join salgrade s
330     on (t.sal_avg between s.LOSAL and s.HISAL)
331 );
332 
333 
334 select * from dept;
335 
336 /*selected the lowest avg salary‘s deptment‘s deptname*/
337 select t1.deptno, dname, sal_avg, grade from 
338     (
339         select deptno, to_char(sal_avg, ‘999999.99‘) sal_avg, grade 
340         from (select deptno, avg(sal) sal_avg from emp group by deptno) t 
341         join salgrade s
342         on (t.sal_avg between s.LOSAL and s.HISAL)
343     ) t1
344 join 
345     dept 
346 on 
347     t1.deptno = dept.DEPTNO
348 where 
349     t1.grade = 
350     (
351         select min(grade) from (
352             select deptno, to_char(sal_avg, ‘999999.99‘) sal_avg, grade 
353             from (select deptno, avg(sal) sal_avg from emp group by deptno) t 
354             join salgrade s
355             on (t.sal_avg between s.LOSAL and s.HISAL)
356         )
357     ); 
358 
359 /*create view*/
360 create or replace view v$_dept_avg_sal_info as 
361     select deptno, to_char(sal_avg, ‘999999.99‘) sal_avg, grade 
362     from (select deptno, avg(sal) sal_avg from emp group by deptno) t 
363     join salgrade s
364     on (t.sal_avg between s.LOSAL and s.HISAL)
365 
366 select * from V$_DEPT_AVG_SAL_INFO;
367 
368 
369 /*selected the lowest avg salary‘s deptment‘s deptname by view*/
370 
371 select t1.deptno, dname, sal_avg, grade from 
372     V$_DEPT_AVG_SAL_INFO t1
373 join 
374     dept 
375 on 
376     t1.deptno = dept.DEPTNO
377 where 
378     t1.grade = 
379     (
380         select min(grade) from V$_DEPT_AVG_SAL_INFO
381     ); 
382 
383 select max(sal) 
384 from 
385     emp 
386 where 
387     EMPNO not in (select distinct mgr from emp where MGR is not null);
388 
389 
390 select ename 
391 from 
392     emp 
393 where 
394     empno in (select distinct mgr from emp where MGR is not null) 
395     and 
396     SAL > (
397         select max(sal) 
398         from 
399             emp 
400         where 
401             EMPNO not in (select distinct mgr from emp where MGR is not null)
402     )
403 
404 
405 select * from user_views;
406 
407 select empno, ename, rownum from emp order by empno desc;
408 
409 select empno, ename from emp where rownum <= 5;
410 
411 select rownum r, ename from emp;
412  
413 select ename from (select rownum r, ename from emp) where r > 10;
414 
415 select ename, sal from emp order by sal desc;
416 
417 select ename, sal from (select ename, sal from EMP order by sal desc) where rownum <= 5;
418 
419 select ename,sal 
420 from (select ename, sal, rownum r from (select ename, sal from emp order by SAL desc))
421 where r >= 6 and r <= 10;
422 
423 
424 
425 select * from PRESENT;

  1 /********************************SCOTT Database*******************************/
  2 select * from EMP;
  3 select * from DEPT;
  4 select * from SALGRADE;
  5 
  6 select ename, sal*12 from emp;
  7 
  8 /*system empty table*/
  9 select * from dual;
 10 select 2*3 from dual;
 11 
 12 select sysdate from dual;
 13 /*alias*/
 14 select ename, sal*12 annual_sal from emp;
 15 /*alias with space*/
 16 select ename, sal*12 "annual sal" from emp;
 17 
 18 /*0 not equal null value*/
 19 select ename, comm from emp;
 20 
 21 /*year salary + comm, any contains empty‘s math operation result is empty*/
 22 select ename, sal*12 + comm from emp;
 23 
 24 select ename||sal from emp;
 25 
 26 /*concat string*/
 27 select ename || ‘abcdefg‘ from emp;
 28 
 29 /*2 ‘ instead of 1 ‘*/
 30 select ename || ‘abcdefg‘‘abcd‘ from emp;
 31 
 32 select deptno from emp;
 33 
 34 /*remove duplicate*/
 35 select distinct deptno from emp;
 36 
 37 select distinct deptno, job from emp;
 38 
 39 select * from emp where deptno = 10;
 40 
 41 select * from EMP where ename = ‘CLARK‘;
 42 
 43 select ename, sal from emp where SAL > 1500; 
 44 
 45 select ename, sal from emp where deptno <> 10;
 46 
 47 select ename, sal from emp where ename > ‘CBA‘;
 48 
 49 select ename, sal from emp where sal between 800 and 1500;
 50 
 51 select ename, sal from emp where sal >= 800 and sal <= 1500;
 52 
 53 /*empty value*/
 54 select ename, sal, comm from emp where comm = null;
 55 
 56 select ename, sal, comm from emp where comm is null;
 57 
 58 select ename, sal, comm from emp where comm is not null;
 59 
 60 select ename, sal, comm from emp where sal in (800, 1500, 2000);
 61 
 62 select ename, sal, comm from emp where ename in (‘SMITH‘, ‘KING‘, ‘ABC‘);
 63 
 64 select ename, sal from emp where DEPTNO = 10 and sal > 1000;
 65 
 66 select ename, sal from emp where DEPTNO = 10 or sal > 1000; 
 67 
 68 select ename, sal from emp where DEPTNO = 10 and sal not in (800, 1500);
 69 
 70 /*% means 0 or more*/
 71 select ename from emp where ENAME like ‘%ALL%‘;
 72 
 73 select ename from emp where ename like ‘_A%‘;
 74 
 75 /*contains % in the selected rows need escape sequence*/
 76 
 77 select ename from emp where ENAME like ‘%\%%‘;
 78 
 79 /*default escapse sequence is \ but we can defintion by use <escape> ‘$‘ */
 80 select ename from emp where ename like ‘%$%%‘ escape ‘$‘;
 81 
 82 select * from DEPT;
 83 
 84 /*order by asc desc defalut is asc*/
 85 select * from DEPT order by DEPTNO desc;
 86 
 87 select empno, ename from emp;
 88 
 89 select empno, ename from emp order by EMPNO asc;
 90 
 91 select empno, ename from emp order by EMPNO desc;
 92 
 93 select empno, ename from emp where deptno <> 10 order by empno asc;
 94 
 95 select ename, sal, deptno from emp order by deptno asc; 
 96 
 97 select ename, sal, deptno from emp order by deptno asc, ename desc;
 98 
 99 select ename, sal*12 annual_sal from emp where ename not like ‘_A%‘ and sal > 800 order by sal desc; 
100 
101 select lower(ename) from emp
102 
103 select ename from emp where lower(ename) like ‘_a%‘;
104 
105 select ename from emp where ename like ‘_a%‘ or ename like ‘_A%‘;
106 
107 select substr(ename, 1, 3) from emp;
108 
109 select substr(ename, 2, 3) from emp;
110 
111 select chr(65) from dual;
112 
113 select ascii(‘A‘) from dual;
114 
115 select round(23.652) from dual;
116 
117 select round(23.652, 2) from dual;
118 
119 select round(23.652, -1) from dual;
120 
121 /* 9 means number, is this position has no number, it will not be displayed
122    ‘$99,999.9999‘ --> $800.0000
123    ‘$99,999.9999‘ --> $1,500.0000
124    ‘L99,999.9999‘ --> Y1,500.0000
125    ‘$00000.0000‘ --> $00800.0000
126    ‘$00000.0000‘ --> $01500.0000
127    
128    to_char
129 */
130 
131 select to_char(sal, ‘$99,999.9999‘) from emp;
132 
133 select to_char(sal, ‘$00000.0000‘) from emp;
134 
135 select hiredate from emp;
136 
137 /* Date format
138  YYYY -- year
139  MM   -- month
140  DD   -- day
141  HH   -- 12 hour
142  HH24 -- 24 hour
143  MI   -- minute
144  SS   -- second
145 */
146 select to_char(hiredate, ‘YYYY-MM-DD HH:MI:SS‘) joindate from emp;
147 
148 /*to_date*/
149 select ename, hiredate from emp where HIREDATE > to_date(‘1981-2-20 12:34:56‘, ‘YYYY-MM-DD HH24:MI:SS‘);
150 
151 /*to_number*/
152 select sal from EMP where sal > to_number(‘$1,250.00‘, ‘$9,999.99‘);
153 
154 select ename, sal*12 + comm from emp;
155 
156 
157 /* 
158    function nvl to deal with null value to math operation
159    if comm is null then o instead of null or it will be comm
160 */
161 select ename, sal*12 + nvl(comm, 0) from emp;
162 
163 
164 /*
165    group function : min, max, avg, count, sum   
166 */
167 select max(sal) maxsal from emp;
168 
169 select min(sal) minsal from emp;
170 
171 select avg(sal) avgsal from emp;
172 
173 select to_char(avg(sal),‘999999999.99‘) avgsal from emp;
174 
175 select round(avg(sal),2) avgsal from emp;
176 
177 select sum(sal) from emp;
178 
179 select count(*) records from emp;
180 
181 select count(*) from emp where deptno = 10;
182 
183 select count(ename) from emp;
184 
185 /*count the field which is not null*/
186 select count(comm) from emp;
187 
188 select count(deptno) from emp;
189  
190 select count(distinct deptno) from emp;
191 
192 /*
193     function : group by
194 */
195 
196 /* which department‘s avg salary is highest*/
197 select sal, deptno from emp;
198 
199 
200 /*department avg salary*/
201 select deptno, to_char(avg(sal),‘99999999.99‘) depavgsal from emp group by deptno;
202 
203 select deptno, job, max(sal) maxsal from emp group by deptno, job;
204 
205 /*the highest salary in the company*/
206 select max(sal) from emp;
207 
208 /*who is the highest salary in the company*/
209 select ename from emp where sal = (select max(sal) from emp);
210 
211 /*the highest salary in the department*/
212 select deptno, max(sal) from emp group by deptno;
213 
214 select to_char(avg(sal), ‘99999999.99‘) avgsal, deptno from emp group by deptno;
215 
216 /* having is limited with grouping*/
217 select to_char(avg(sal), ‘99999999.99‘) avgsal, deptno from emp group by deptno having avg(sal) > 2000;
218 
219 select deptno, max(sal) from emp where SAL > 1000 group by deptno having avg(sal) > 2000 order by deptno desc; 
220 
221 select deptno, to_char(avg(sal), ‘99999999.99‘) from emp where sal > 1200 group by deptno having avg(sal) > 1500 order by avg(sal) desc;
222 
223 
224 select ename, sal from emp where SAL = (select max(sal) from emp);
225 
226 select ename, sal from emp where sal > (select avg(sal) from emp);
227 
228 select ename, sal from emp join (select max(sal) maxsal, deptno from emp group by deptno) t on (emp.sal = t.maxsal and emp.deptno = t.deptno);
229 
230 select * from SALGRADE;
231 
232 select deptno, to_char(avg(sal), ‘999999999.99‘) s from emp group by deptno;
233 
234 SELECT dname,grade,to_char(S, ‘999999.999‘) FROM dept,(SELECT deptno,grade,s FROM (SELECT deptno,grade,s FROM (SELECT deptno,avg(sal) s FROM emp GROUP BY deptno),salgrade WHERE s BETWEEN losal AND hisal ORDER BY grade DESC) t WHERE ROWNUM=1) t WHERE dept.deptno=t.deptno;
235 
236 SELECT dname,grade,to_char(S, ‘999999.999‘) FROM dept,(SELECT deptno,grade,s FROM (SELECT deptno,grade,s FROM (SELECT deptno,avg(sal) s FROM emp GROUP BY deptno),salgrade WHERE s BETWEEN losal AND hisal ORDER BY grade DESC) t WHERE ROWNUM=1) t WHERE dept.deptno=t.deptno;
237 
238 
239 /*self table connection*/
240 
241 select empno, ename, mgr from emp;
242 
243 select e1.ename, e2.ename from emp e1, emp e2 where e1.MGR = e2.EMPNO;
244 
245 select ename, dname from EMP, DEPT where emp.DEPTNO = dept.DEPTNO;
246 
247 select ename, dname from EMP join DEPT on (emp.DEPTNO = dept.DEPTNO); 
248 
249 select ename, dname from EMP join DEPT using (deptno);
250 
251 select ename, grade from emp e join salgrade s on (e.SAL between s.LOSAL and s.HISAL);
252 
253 select ename, dname, grade from emp e join dept d on (e.DEPTNO = d.DEPTNO) join salgrade s on (e.SAL between s.LOSAL and s.HISAL) where ename not like ‘_A%‘;  
254 
255 /*left join == left outer join*/
256 select e1.ename, e2.ename from emp e1 left join emp e2 on (e1.mgr = e2.empno);
257 
258 select e1.ename, e2.ename from emp e1 left outer join emp e2 on (e1.mgr = e2.empno);
259 
260 select * from dept;
261 
262 select ename, dname from emp e right join DEPT d on (e.DEPTNO = d.DEPTNO);
263 
264 select ename, dname from emp e right outer join DEPT d on (e.DEPTNO = d.DEPTNO);
265 
266 /* full join */
267 select ename, dname from emp e full join DEPT d on (e.DEPTNO = d.DEPTNO);
268 
269 /*department avg salary*/
270 select deptno, to_char(avg(sal), ‘9999999.99‘) from emp group by deptno;
271 
272 /*department avg salary‘s grade*/
273 select deptno, avg_sal, grade 
274 from (select deptno, to_char(avg(sal), ‘999999.99‘) avg_sal from emp group by deptno) t 
275 join SALGRADE s 
276 on (t.avg_sal between s.LOSAL and s.HISAL);
277 
278 /*salary grade for every employee*/
279 select ename, deptno, grade from emp e join SALGRADE s on (e.SAL between s.LOSAL and s.HISAL);
280 
281 select deptno, to_char(avg(grade), ‘9.9‘) avg_grade
282 from (select ename, deptno, grade from emp e join SALGRADE s on (e.SAL between s.LOSAL and s.HISAL)) t
283 group by t.deptno;
284 
285 /* who is manager*/
286 select ename from emp where EMPNO in (select mgr from emp);
287 
288 select ename from emp where EMPNO in (select distinct mgr from emp);
289 
290 select * from emp;
291 
292 /*select highest salary*/
293 select max(sal) from emp;
294 
295 select distinct e1.sal from emp e1 join emp e2 on (e1.SAL < e2.SAL);
296 
297 /* please don‘t use group function to find the max salary*/
298 select distinct sal from emp where SAL not in (select distinct e1.sal from emp e1 join emp e2 on (e1.SAL < e2.SAL));
299 
300 select deptno, avg_sal from (select to_char(avg(sal), ‘99999.99‘) avg_sal, deptno from emp group by deptno) 
301 where avg_sal = (select max(avg_sal) from (select to_char(avg(sal),‘999999.99‘) avg_sal, deptno from emp group by deptno));
302 
303 
304 select max(avg_sal) from (select to_char(avg(sal),‘999999.99‘) avg_sal, deptno from emp group by deptno);
305 select to_char(avg(sal), ‘99999.99‘) avg_sal, deptno from emp group by deptno;
306 
307 
308 /*avg salary is highest*/
309 select deptno, avg_sal from (select to_char(avg(sal), ‘99999.99‘) avg_sal, deptno from emp group by deptno) where avg_sal = (select max(avg_sal) from (select to_char(avg(sal),‘99999.99‘) avg_sal, deptno from emp group by deptno));
310 
311 /*the depatname of the highest avg salary*/
312 select dname from dept where deptno = 
313 (select deptno from (select to_char(avg(sal), ‘99999.99‘) avg_sal, deptno from emp group by deptno) where avg_sal = (select max(avg_sal) from (select to_char(avg(sal),‘99999.99‘) avg_sal, deptno from emp group by deptno)));
314 
315 
316 select avg(sal) sal_avg from emp group by deptno;
317 
318 select deptno, avg(sal) sal_avg from emp group by deptno;
319 
320 select deptno, to_char(sal_avg, ‘999999.99‘) sal_avg, grade 
321 from (select deptno, avg(sal) sal_avg from emp group by deptno) t 
322 join salgrade s
323 on (t.sal_avg between s.LOSAL and s.HISAL);
324 
325 
326 select min(grade) from (
327     select deptno, to_char(sal_avg, ‘999999.99‘) sal_avg, grade 
328     from (select deptno, avg(sal) sal_avg from emp group by deptno) t 
329     join salgrade s
330     on (t.sal_avg between s.LOSAL and s.HISAL)
331 );
332 
333 
334 select * from dept;
335 
336 /*selected the lowest avg salary‘s deptment‘s deptname*/
337 select t1.deptno, dname, sal_avg, grade from 
338     (
339         select deptno, to_char(sal_avg, ‘999999.99‘) sal_avg, grade 
340         from (select deptno, avg(sal) sal_avg from emp group by deptno) t 
341         join salgrade s
342         on (t.sal_avg between s.LOSAL and s.HISAL)
343     ) t1
344 join 
345     dept 
346 on 
347     t1.deptno = dept.DEPTNO
348 where 
349     t1.grade = 
350     (
351         select min(grade) from (
352             select deptno, to_char(sal_avg, ‘999999.99‘) sal_avg, grade 
353             from (select deptno, avg(sal) sal_avg from emp group by deptno) t 
354             join salgrade s
355             on (t.sal_avg between s.LOSAL and s.HISAL)
356         )
357     ); 
358 
359 /*create view*/
360 create or replace view v$_dept_avg_sal_info as 
361     select deptno, to_char(sal_avg, ‘999999.99‘) sal_avg, grade 
362     from (select deptno, avg(sal) sal_avg from emp group by deptno) t 
363     join salgrade s
364     on (t.sal_avg between s.LOSAL and s.HISAL)
365 
366 select * from V$_DEPT_AVG_SAL_INFO;
367 
368 
369 /*selected the lowest avg salary‘s deptment‘s deptname by view*/
370 
371 select t1.deptno, dname, sal_avg, grade from 
372     V$_DEPT_AVG_SAL_INFO t1
373 join 
374     dept 
375 on 
376     t1.deptno = dept.DEPTNO
377 where 
378     t1.grade = 
379     (
380         select min(grade) from V$_DEPT_AVG_SAL_INFO
381     ); 
382 
383 select max(sal) 
384 from 
385     emp 
386 where 
387     EMPNO not in (select distinct mgr from emp where MGR is not null);
388 
389 
390 select ename 
391 from 
392     emp 
393 where 
394     empno in (select distinct mgr from emp where MGR is not null) 
395     and 
396     SAL > (
397         select max(sal) 
398         from 
399             emp 
400         where 
401             EMPNO not in (select distinct mgr from emp where MGR is not null)
402     )
403 
404 
405 select * from user_views;
406 
407 select empno, ename, rownum from emp order by empno desc;
408 
409 select empno, ename from emp where rownum <= 5;
410 
411 select rownum r, ename from emp;
412  
413 select ename from (select rownum r, ename from emp) where r > 10;
414 
415 select ename, sal from emp order by sal desc;
416 
417 select ename, sal from (select ename, sal from EMP order by sal desc) where rownum <= 5;
418 
419 select ename,sal 
420 from (select ename, sal, rownum r from (select ename, sal from emp order by SAL desc))
421 where r >= 6 and r <= 10;
422 
423 
424 
425 select * from PRESENT;