Oracle PL/SQL/Analytical Functions/STDDEV
STDDEV([DISTINCT | ALL] value) [OVER (analytic_clause)]: returns the standard deviation value
<source lang="sql">
SQL> SQL> SQL> create table TestTable (
2 x number primary key, 3 y number 4 );
Table created. SQL> insert into TestTable values (1, 7 ); 1 row created. SQL> insert into TestTable values (2, 1 ); 1 row created. SQL> insert into TestTable values (3, 2 ); 1 row created. SQL> insert into TestTable values (4, 5 ); 1 row created. SQL> insert into TestTable values (5, 7 ); 1 row created. SQL> insert into TestTable values (6, 34 ); 1 row created. SQL> insert into TestTable values (7, 32 ); 1 row created. SQL> insert into TestTable values (8, 43 ); 1 row created. SQL> insert into TestTable values (9, 87 ); 1 row created. SQL> SQL> select * from TestTable;
X Y
----------
1 7 2 1 3 2 4 5 5 7 6 34 7 32 8 43 9 87
9 rows selected. SQL> SQL> -- STDDEV([DISTINCT | ALL] value) [OVER (analytic_clause)]: returns the standard deviation value. SQL> SQL> -- STDDEV([DISTINCT | ALL] value) [OVER (analytic_clause)] SQL> SQL> SELECT STDDEV(y) FROM TestTable;
STDDEV(Y)
28.3847573 SQL> SQL> drop table TestTable; Table dropped. SQL> SQL> SQL> SQL>
</source>
STDDEV(x): get the standard deviation of x
<source lang="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"), 6661.78, "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"), 6544.78, "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"), 2344.78, "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"), 4322.78,"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"), 7897.78,"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"), 1232.78,"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 6661.78 Vancouver Tester 03 James Smith 12-DEC-78 15-MAR-90 6544.78 Vancouver Tester 04 Celia Rice 24-OCT-82 21-APR-99 2344.78 Vancouver Manager 05 Robert Black 15-JAN-84 08-AUG-98 2334.78 Vancouver Tester 06 Linda Green 30-JUL-87 04-JAN-96 4322.78 New York Tester 07 David Larry 31-DEC-90 12-FEB-98 7897.78 New York Manager 08 James Cat 17-SEP-96 15-APR-02 1232.78 Vancouver Tester 8 rows selected. SQL> SQL> SQL> SQL> SQL> -- STDDEV() SQL> SQL> --You use STDDEV(x) to get the standard deviation of x: defined as being the square root of the variance. SQL> SQL> SQL> SELECT STDDEV(salary)
2 FROM employee;
STDDEV(SALARY)
2662.82724
SQL> SQL> SQL> SQL> -- clean the table SQL> drop table Employee
2 /
Table dropped. SQL> SQL>
</source>