Oracle PL/SQL/Subquery/Virtual Table
Версия от 13:45, 26 мая 2010; (обсуждение)
First three rows from subquery
SQL>
SQL> create table history
2 ( empno NUMBER(4)
3 , beginyear NUMBER(4)
4 , begindate DATE
5 , enddate DATE
6 , deptno NUMBER(2)
7 , sal NUMBER(6,2)
8 , comments VARCHAR2(60)
9 , constraint H_PK primary key (empno,begindate)
10 , constraint H_BEG_END check (begindate < enddate)
11 ) ;
Table created.
SQL>
SQL>
SQL> alter session set NLS_DATE_FORMAT="DD-MM-YYYY";
Session altered.
SQL>
SQL> insert into history values (1,2000,"01-02-2000", NULL ,20, 800,"restarted");
1 row created.
SQL> insert into history values (2,1995,"01-10-1995","01-11-2009",30,1700,"");
1 row created.
SQL> insert into history values (2,2009,"01-11-2009", NULL ,30,1600,"just hired");
1 row created.
SQL> insert into history values (3,1986,"01-10-1986","01-08-1987",20,1000,"");
1 row created.
SQL> insert into history values (3,1987,"01-08-1987","01-01-1989",30,1000,"On training");
1 row created.
SQL> insert into history values (3,2000,"01-02-2000", NULL ,30,1250,"");
1 row created.
SQL>
SQL> select *
2 from (select empno, sal
3 from history
4 order by sal desc)
5 where rownum <= 3;
EMPNO SAL
---------- ----------
2 1700
2 1600
3 1250
SQL>
SQL> drop table history;
Table dropped.
SQL>
Format result from subquery
SQL>
SQL>
SQL> select username,
2 to_number( substr( data, 1, 10 ) ) cnt,
3 to_number( substr( data, 11 ) ) avg
4 from (
5 select a.username, (select to_char( count(*), "fm0000000009" ) || avg(object_id) from all_objects b where b.owner = a.username) data
6 from all_users a
7 )
8 /
USERNAME CNT AVG
------------------------------ ---------- ----------
SYS 6520 5009.74064
SYSTEM 422 6095.87678
OUTLN 7 1172.57143
DIP 0
TSMSYS 2 8606.5
INV15 2 16237.5
DBSNMP 46 9592.65217
INV10 2 16227.5
CTXSYS 338 9877.92012
XDB 334 10800.7485
ANONYMOUS 0
USERNAME CNT AVG
------------------------------ ---------- ----------
MDSYS 458 11667.2009
HR 34 12104.5
FLOWS_FILES 11 12717.2727
FLOWS_020100 1085 12813.424
sqle 530 16254.6849
INV11 2 16229.5
INV12 2 16231.5
INV13 2 16233.5
INV14 2 16235.5
PLSQL 0
INV16 2 16239.5
USERNAME CNT AVG
------------------------------ ---------- ----------
INV17 2 16241.5
INV18 2 16243.5
INV19 2 16245.5
INV20 2 16247.5
DEFINER 4 16250.5
27 rows selected.
SQL>
Select from virtual table (sub query) with rownum
SQL>
SQL>
SQL> -- create demo table
SQL> create table Employee(
2 ID VARCHAR2(4 BYTE) NOT NULL,
3 First_Name VARCHAR2(10 BYTE),
4 Last_Name VARCHAR2(10 BYTE),
5 Start_Date DATE,
6 End_Date DATE,
7 Salary Number(8,2),
8 City VARCHAR2(10 BYTE),
9 Description VARCHAR2(15 BYTE)
10 )
11 /
Table created.
SQL>
SQL> -- prepare data
SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values ("01","Jason", "Martin", to_date("19960725","YYYYMMDD"), to_date("20060725","YYYYMMDD"), 1234.56, "Toronto", "Programmer")
3 /
1 row created.
SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("02","Alison", "Mathews", to_date("19760321","YYYYMMDD"), to_date("19860221","YYYYMMDD"), 2334.78, "Vancouver","Tester")
3 /
1 row created.
SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("03","James", "Smith", to_date("19781212","YYYYMMDD"), to_date("19900315","YYYYMMDD"), 2334.78, "Vancouver","Tester")
3 /
1 row created.
SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("04","Celia", "Rice", to_date("19821024","YYYYMMDD"), to_date("19990421","YYYYMMDD"), 2334.78, "Vancouver","Manager")
3 /
1 row created.
SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("05","Robert", "Black", to_date("19840115","YYYYMMDD"), to_date("19980808","YYYYMMDD"), 2334.78, "Vancouver","Tester")
3 /
1 row created.
SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("06","Linda", "Green", to_date("19870730","YYYYMMDD"), to_date("19960104","YYYYMMDD"), 2334.78,"New York", "Tester")
3 /
1 row created.
SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("07","David", "Larry", to_date("19901231","YYYYMMDD"), to_date("19980212","YYYYMMDD"), 2334.78,"New York", "Manager")
3 /
1 row created.
SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("08","James", "Cat", to_date("19960917","YYYYMMDD"), to_date("20020415","YYYYMMDD"), 2334.78,"Vancouver", "Tester")
3 /
1 row created.
SQL>
SQL>
SQL>
SQL> -- display data in the table
SQL> select * from Employee
2 /
ID FIRST_NAME LAST_NAME START_DAT END_DATE SALARY CITY DESCRIPTION
---- ---------- ---------- --------- --------- ---------- ---------- ---------------
01 Jason Martin 25-JUL-96 25-JUL-06 1234.56 Toronto Programmer
02 Alison Mathews 21-MAR-76 21-FEB-86 2334.78 Vancouver Tester
03 James Smith 12-DEC-78 15-MAR-90 2334.78 Vancouver Tester
04 Celia Rice 24-OCT-82 21-APR-99 2334.78 Vancouver Manager
05 Robert Black 15-JAN-84 08-AUG-98 2334.78 Vancouver Tester
06 Linda Green 30-JUL-87 04-JAN-96 2334.78 New York Tester
07 David Larry 31-DEC-90 12-FEB-98 2334.78 New York Manager
08 James Cat 17-SEP-96 15-APR-02 2334.78 Vancouver Tester
8 rows selected.
SQL>
SQL> -- select from virtual table
SQL>
SQL>
SQL> SELECT id "Emp #", first_name "Name", salary "Salary",
2 ROWNUM rank
3 FROM
4 (SELECT id, first_name, salary FROM employee ORDER BY salary desc);
Emp Name Salary RANK
---- ---------- ---------- ----------
04 Celia 2334.78 1
02 Alison 2334.78 2
03 James 2334.78 3
08 James 2334.78 4
05 Robert 2334.78 5
06 Linda 2334.78 6
07 David 2334.78 7
01 Jason 1234.56 8
8 rows selected.
SQL>
SQL>
SQL>
SQL>
SQL>
SQL>
SQL>
SQL> -- clean the table
SQL> drop table Employee;
Table dropped.
SQL>
SQL>