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SQL series (basic) - Chapter 2 limiting and sorting data
2022-07-05 20:53:00 【Full stack programmer webmaster】
Hello everyone , I meet you again , I'm the king of the whole stack , I've prepared for you today Idea Registration code .
Better look ↑ Code click VIEW PLAN Chapter two Constrain and sort data
1. stay emp The salary selected in the table is between 1500 To 2500 Information about our employees ;
Be careful ： Use between Lower boundary and On the upper border . Conditions include boundary values ;
[email protected]>l
1 select * from emp
2* where sal between 1500 and 2500
[email protected]>/
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
2. stay emp In the table, select the location in 20,30 Information about employees in the Department ;
[email protected]>select *from emp
2 where deptno in (20,30);
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7369 SMITH CLERK 7902 17-DEC-80 800 20
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7566 JONES MANAGER 7839 02-APR-81 2975 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
11 rows selected.
3. stay emp The selection in the table is located in the employee's name, including uppercase characters ‘A’ Information about our employees ;
[email protected]>select * from emp
2 where ename like '%A%';
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7 rows selected.
Be careful ： Suppose the name of the query includes % perhaps _ , And when you query, you need to query this kind of information , Transposition code is needed .
Be careful ： wildcard %, Express 0 Or more than one character ; wildcard _, Express 1 It's like two characters .
3.1 Create with emp Table structure the same table ;
[email protected]>create table emp_n /* Reference emp Table create a new table emp_n */
2 as select * from emp where 1=2; /* Add where 1=2 Consistent table structure has no data */
Table created.
[email protected]>select * from emp_n;
no rows selected
3.2 Add test data including wildcards ;
[email protected]>insert into emp_n(empno,ename,sal) values(&empno,&ename,&sal);
Enter value for empno: 1001
Enter value for ename: 'whwh%gogo'
Enter value for sal: 1000
old 1: insert into emp_n(empno,ename,sal) values(&empno,&ename,&sal)
new 1: insert into emp_n(empno,ename,sal) values(1001,'whwh%gogo',1000)
1 row created.
[email protected]>/
Enter value for empno: 1002
Enter value for ename: '%whwh'
Enter value for sal: 2000
old 1: insert into emp_n(empno,ename,sal) values(&empno,&ename,&sal)
new 1: insert into emp_n(empno,ename,sal) values(1002,'%whwh',2000)
1 row created.
[email protected]>/
Enter value for empno: 1003
Enter value for ename: 'whwh_gogo'
Enter value for sal: 3000
old 1: insert into emp_n(empno,ename,sal) values(&empno,&ename,&sal)
new 1: insert into emp_n(empno,ename,sal) values(1003,'whwh_gogo',3000)
1 row created.
[email protected]>/
Enter value for empno: 1004
Enter value for ename: '_gogo'
Enter value for sal: 4000
old 1: insert into emp_n(empno,ename,sal) values(&empno,&ename,&sal)
new 1: insert into emp_n(empno,ename,sal) values(1004,'_gogo',4000)
1 row created.
[email protected]>commit;
Commit complete.
[email protected]>select * from emp_n;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
1001 whwh%gogo 1000
1002 %whwh 2000
1003 whwh_gogo 3000
1004 _gogo 4000
3.3 The usage of transposition code .（ Here to \ As transposition code . Transposition codes can also specify other characters ）
example ： The search includes % The recorded information of .
[email protected]>select * from emp_n
2 where ename like '%\%%' escape '\';
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
1001 whwh%gogo 1000
1002 %whwh 2000
[email protected]>select * from emp_n
2 where ename like '%\%%';
no rows selected
example ： Search for % Record information at the beginning ;
[email protected]>select * from emp_n
2 where ename like '\%%' escape '\';
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
1002 %whwh 2000
example ： The search includes _ The recorded information of .
[email protected]>select * from emp_n
2 where ename like '%\_%' escape '\';
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
1003 whwh_gogo 3000
1004 _gogo 4000
example ： Search for _ Record information at the beginning ;
[email protected]>select * from emp_n
2 where ename like '\_%' escape '\';
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
1004 _gogo 4000
4 The use of composite conditions
4.1 about and The combination of conditions （ To be able to between...and... convert ）
example ： stay emp The salary selected in the table is between 2000 To 3000 Information about our employees .
[email protected]>select * from emp
2 where sal>=2000 and sal<=3000;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7566 JONES MANAGER 7839 02-APR-81 2975 20
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7902 FORD ANALYST 7566 03-DEC-81 3000 20
[email protected]>select * from emp
2 where sal between 2000 and 3000;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7566 JONES MANAGER 7839 02-APR-81 2975 20
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7902 FORD ANALYST 7566 03-DEC-81 3000 20
4.2 about or Conditional compounding （ To be able to in() convert ）
example ： stay emp Select from the table 10 Number and 20 Employee information of department No ;
[email protected]>select * from emp
2 where deptno=10 or deptno=20;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7369 SMITH CLERK 7902 17-DEC-80 800 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7839 KING PRESIDENT 17-NOV-81 5000 10
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7934 MILLER CLERK 7782 23-JAN-82 1300 10
8 rows selected.
[email protected]>select * from emp
2 where deptno in (10,20);
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7369 SMITH CLERK 7902 17-DEC-80 800 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7839 KING PRESIDENT 17-NOV-81 5000 10
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7934 MILLER CLERK 7782 23-JAN-82 1300 10
8 rows selected.
5 For sorting the data in the table
5.1 asc It means to arrange in ascending order according to the given fields （ Default ascending order ）
desc It means to arrange in descending order according to the given fields
example ： take emp In the table 10 The employee information of department No sal The columns are arranged in ascending order
[email protected]>select * from emp
2 where deptno=10;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7839 KING PRESIDENT 17-NOV-81 5000 10
7934 MILLER CLERK 7782 23-JAN-82 1300 10
[email protected]>select * from emp
2 where deptno=10
3 order by sal asc;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7839 KING PRESIDENT 17-NOV-81 5000 10
[email protected]>select * from emp
2 where deptno=10
3 order by sal;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7839 KING PRESIDENT 17-NOV-81 5000 10
example ： take emp In the table 20 The employee information of department No sal The columns are arranged in descending order
[email protected]>select * from emp
2 where deptno=20
3 order by sal desc;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
5.2 hypothesis order by Followed by multiple fields . Then, the result set is set according to section 1 Fields to sort 【 Conditions 1】.
And then press... Again 2 Fields to sort 【 Conditions 2】;
Be careful ：【 Conditions 1】 Suppose that according to section 1 When a field can't be separated in order . In accordance with article 2 Field sort .
asc perhaps desc Affected fields , But the field next to it .
example ： take emp In the table 10 For the employee information of department number, press sal Descending order ,empno Ascending order ;
[email protected]>select * from emp
2 where deptno=10
3 order by sal desc,empno asc;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7839 KING PRESIDENT 17-NOV-81 5000 10
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7934 MILLER CLERK 7782 23-JAN-82 1300 10
example ： take emp In the table 20 The employee information of department No empno Descending order ,sal Ascending order ;
[email protected]>select * from emp
2 where deptno=20
3 order by empno desc,sal asc;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
5.3 In addition to being able to use field sorting . You can also sort by using the order in which the fields are located ;
Determine the order of fields in the table .
[email protected]>set lines 100
[email protected]>desc emp;
/*
* Tips ： This line of code is too long , The system automatically comments without highlighting . One click Copy removes system comments
* Name Null? Type ----------------------------------------------------- -------- ------------------------------------ EMPNO NOT NULL NUMBER(4) ENAME VARCHAR2(10) JOB VARCHAR2(9) MGR NUMBER(4) HIREDATE DATE SAL NUMBER(7,2) COMM NUMBER(7,2) DEPTNO NUMBER(2) example ： take emp In the table 10 For the employee information of department number, press sal Descending order ,empno Ascending order . [email protected]>select * from emp 2 where deptno=10 3 order by 6 desc,1 asc; EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO---------- ---------- --------- ---------- --------- ---------- ---------- ---------- 7839 KING PRESIDENT 17-NOV-81 5000 10 7782 CLARK MANAGER 7839 09-JUN-81 2450 10 7934 MILLER CLERK 7782 23-JAN-82 1300 10 example ： take emp In the table 20 The employee information of department No empno Descending order ,sal Ascending order ;[email protected]>select * from emp 2 where deptno=20 3 order by 1 desc,6 asc; EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO---------- ---------- --------- ---------- --------- ---------- ---------- ---------- 7902 FORD ANALYST 7566 03-DEC-81 3000 20 7876 ADAMS CLERK 7788 23-MAY-87 1100 20 7788 SCOTT ANALYST 7566 19-APR-87 3000 20 7566 JONES MANAGER 7839 02-APR-81 2975 20 7369 SMITH CLERK 7902 17-DEC-80 800 20 5.4 Besides being able to use number Type of field , You can also use string or time type fields to sort . Be careful ： String sort ： According to the character corresponding to ASCII The sequence of the codes . Date sort ： Sort by date , The more time goes on, the more ; example ： take emp The employees in the table are in accordance with job Ascending 、ename In descending order ;（ According to the first Job Sort . alike job Press ename Descending ）[email protected]>select * from emp 2 order by job asc,ename desc; EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO---------- ---------- --------- ---------- --------- ---------- ---------- ---------- 7788 SCOTT ANALYST 7566 19-APR-87 3000 20 7902 FORD ANALYST 7566 03-DEC-81 3000 20 7369 SMITH CLERK 7902 17-DEC-80 800 20 7934 MILLER CLERK 7782 23-JAN-82 1300 10 7900 JAMES CLERK 7698 03-DEC-81 950 30 7876 ADAMS CLERK 7788 23-MAY-87 1100 20 7566 JONES MANAGER 7839 02-APR-81 2975 20 7782 CLARK MANAGER 7839 09-JUN-81 2450 10 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30 7839 KING PRESIDENT 17-NOV-81 5000 10 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 3014 rows selected. example ： take emp The employees in the table are in accordance with HIREDATE Ascending ,sal Descending order （ hypothesis HIREDATE Again , according to sal Descending ） First the HIREDATE Display format settings [email protected]>alter session set nls_date_format='yyyy-mm-dd';Session [email protected]>select * from emp 2 order by hiredate asc,sal desc; EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO---------- ---------- --------- ---------- ---------- ---------- ---------- ---------- 7369 SMITH CLERK 7902 1980-12-17 800 20 7499 ALLEN SALESMAN 7698 1981-02-20 1600 300 30 7521 WARD SALESMAN 7698 1981-02-22 1250 500 30 7566 JONES MANAGER 7839 1981-04-02 2975 20 7698 BLAKE MANAGER 7839 1981-05-01 2850 30 7782 CLARK MANAGER 7839 1981-06-09 2450 10 7844 TURNER SALESMAN 7698 1981-09-08 1500 0 30 7654 MARTIN SALESMAN 7698 1981-09-28 1250 1400 30 7839 KING PRESIDENT 1981-11-17 5000 10 7902 FORD ANALYST 7566 1981-12-03 3000 20 7900 JAMES CLERK 7698 1981-12-03 950 30 7934 MILLER CLERK 7782 1982-01-23 1300 10 7788 SCOTT ANALYST 7566 1987-04-19 3000 20 7876 ADAMS CLERK 7788 1987-05-23 1100 2014 rows selected. 6. Sort with aliases in the result set . example ： according to emp The annual salary of employees in the table （sal*12） Sort [email protected]>select empno,ename,hiredate,sal*12 year_sal 2 from emp 3 order by year_sal desc; EMPNO ENAME HIREDATE YEAR_SAL---------- ---------- ---------- ---------- 7839 KING 1981-11-17 60000 7902 FORD 1981-12-03 36000 7788 SCOTT 1987-04-19 36000 7566 JONES 1981-04-02 35700 7698 BLAKE 1981-05-01 34200 7782 CLARK 1981-06-09 29400 7499 ALLEN 1981-02-20 19200 7844 TURNER 1981-09-08 18000 7934 MILLER 1982-01-23 15600 7521 WARD 1981-02-22 15000 7654 MARTIN 1981-09-28 15000 7876 ADAMS 1987-05-23 13200 7900 JAMES 1981-12-03 11400 7369 SMITH 1980-12-17 960014 rows selected. Be careful ： Of course, you can also follow strings 、 The date is sorted by the corresponding alias ; 7. Suppose the sorted fields include null value , What will happen ？ Be careful ： When comparing the size of fields ,null It's worth more than anything ; example ：emp The information of the employees in the table is in accordance with comm Descending order ;[email protected]>select * from emp 2 order by comm desc; EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO---------- ---------- --------- ---------- ---------- ---------- ---------- ---------- 7369 SMITH CLERK 7902 1980-12-17 800 20 7782 CLARK MANAGER 7839 1981-06-09 2450 10 7902 FORD ANALYST 7566 1981-12-03 3000 20 7900 JAMES CLERK 7698 1981-12-03 950 30 7876 ADAMS CLERK 7788 1987-05-23 1100 20 7566 JONES MANAGER 7839 1981-04-02 2975 20 7698 BLAKE MANAGER 7839 1981-05-01 2850 30 7934 MILLER CLERK 7782 1982-01-23 1300 10 7788 SCOTT ANALYST 7566 1987-04-19 3000 20 7839 KING PRESIDENT 1981-11-17 5000 10 7654 MARTIN SALESMAN 7698 1981-09-28 1250 1400 30 7521 WARD SALESMAN 7698 1981-02-22 1250 500 30 7499 ALLEN SALESMAN 7698 1981-02-20 1600 300 30 7844 TURNER SALESMAN 7698 1981-09-08 1500 0 3014 rows selected. Be careful ：null Sorting between values does not take into account （ because Null and null Can't compare size between ） Suppose I want to comm Change the value part to the top , What should I do ？[email protected]>select * from emp 2 order by comm desc nulls last; EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO---------- ---------- --------- ---------- ---------- ---------- ---------- ---------- 7654 MARTIN SALESMAN 7698 1981-09-28 1250 1400 30 7521 WARD SALESMAN 7698 1981-02-22 1250 500 30 7499 ALLEN SALESMAN 7698 1981-02-20 1600 300 30 7844 TURNER SALESMAN 7698 1981-09-08 1500 0 30 7788 SCOTT ANALYST 7566 1987-04-19 3000 20 7839 KING PRESIDENT 1981-11-17 5000 10 7876 ADAMS CLERK 7788 1987-05-23 1100 20 7900 JAMES CLERK 7698 1981-12-03 950 30 7902 FORD ANALYST 7566 1981-12-03 3000 20 7934 MILLER CLERK 7782 1982-01-23 1300 10 7698 BLAKE MANAGER 7839 1981-05-01 2850 30 7566 JONES MANAGER 7839 1981-04-02 2975 20 7369 SMITH CLERK 7902 1980-12-17 800 20 7782 CLARK MANAGER 7839 1981-06-09 2450 1014 rows selected. Empathy ： Verify by yourself Ascending array [email protected]>select * from emp 2 order by comm asc nulls first;</span>
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