STDDEV_POP

Deviation

----------

3909.36575

Analytic Examples

The query in the following example returns the cumulative standard deviation of the salaries in Department 80 in the sample table hr.employees, ordered by hire_date:

SELECT last_name, salary,

STDDEV(salary) OVER (ORDER BY hire_date) "StdDev"

FROM employees

WHERE department_id = 30;

STDDEV_POP

Syntax stddev_pop::=

OVER ( analytic_clause )

STDDEV_POP ( expr )

See Also: "Analytic Functions" on page 6-10 for information on syntax, semantics, and restrictions

Purpose

STDDEV_POP computes the population standard deviation and returns the square root of the population variance. You can use it as both an aggregate and analytic function.

Functions 6-149

STDDEV_POP

The expr is a number expression, and the function returns a value of type NUMBER. This function is the same as the square root of the VAR_POP function. When VAR_ POP returns null, this function returns null.

See Also:

■"Aggregate Functions" on page 6-8 and VAR_POP on page 6-202

■"About SQL Expressions" on page 4-2 for information on valid forms of expr

Aggregate Example

The following example returns the population and sample standard deviations of the amount of sales in the sample table sh.sales:

SELECT STDDEV_POP(amount_sold) "Pop",

STDDEV_SAMP(amount_sold) "Samp"

FROM sales;

Analytic Example

The following example returns the population standard deviations of salaries in the sample hr.employees table by department:

SELECT department_id, last_name, salary,

STDDEV_POP(salary) OVER (PARTITION BY department_id) AS pop_std FROM employees;

6-150 Oracle9i SQL Reference

STDDEV_SAMP

STDDEV_SAMP

Syntax stddev_samp::=

OVER ( analytic_clause )

STDDEV_SAMP ( expr )

See Also: "Analytic Functions" on page 6-10 for information on syntax, semantics, and restrictions

Purpose

STDDEV_SAMP computes the cumulative sample standard deviation and returns the square root of the sample variance. You can use it as both an aggregate and analytic function.

The expr is a number expression, and the function returns a value of type NUMBER. This function is same as the square root of the VAR_SAMP function. When VAR_ SAMP returns null, this function returns null.

See Also:

■"Aggregate Functions" on page 6-8 and VAR_SAMP on page 6-204

■"About SQL Expressions" on page 4-2 for information on valid forms of expr

Aggregate Example

The following example returns the population and sample standard deviations of the amount of sales in the sample table sh.sales:

SELECT STDDEV_POP(amount_sold) "Pop",

STDDEV_SAMP(amount_sold) "Samp"

FROM sales;

Functions 6-151

SUBSTR

Analytic Example

The following example returns the sample standard deviation of salaries in the employees table by department:

SELECT department_id, last_name, hire_date, salary, STDDEV_SAMP(salary) OVER (PARTITION BY department_id

ORDER BY hire_date

ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS cum_sdev

SUBSTR

Syntax substr::=

SUBSTR

SUBSTRB

, substring_length

SUBSTR2

SUBSTR4

6-152 Oracle9i SQL Reference

SUBSTR

Purpose

The "substring" functions return a portion of string, beginning at character position, substring_length characters long. SUBSTR calculates lengths using characters as defined by the input character set. SUBSTRB uses bytes instead of characters. SUBSTRC uses Unicode complete characters. SUBSTR2 uses UCS2 codepoints. SUBSTR4 uses UCS4 codepoints.

■If position is 0, then it is treated as 1.

■If position is positive, then Oracle counts from the beginning of string to find the first character.

■If position is negative, then Oracle counts backward from the end of string.

■If substring_length is omitted, then Oracle returns all characters to the end of string. If substring_length is less than 1, then a null is returned.

string can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The return value is the same datatype as string. Floating-point numbers passed as arguments to SUBSTR are automatically converted to integers.

Examples

The following example returns several specified substrings of "ABCDEFG":

SELECT SUBSTR(’ABCDEFG’,3,4) "Substring"

FROM DUAL;

Substring

---------

CDEF

SELECT SUBSTR(’ABCDEFG’,-5,4) "Substring"

FROM DUAL;

Substring

---------

CDEF

Assume a double-byte database character set:

SELECT SUBSTRB(’ABCDEFG’,5,4.2) "Substring with bytes" FROM DUAL;

Substring with bytes

--------------------

CD

Functions 6-153

SUM

SUM

Syntax sum::=

See Also: "Analytic Functions" on page 6-10 for information on syntax, semantics, and restrictions

Purpose

SUM returns the sum of values of expr. You can use it as an aggregate or analytic function.

If you specify DISTINCT, then you can specify only the query_partition_ clause of the analytic_clause. The order_by_clause and windowing_ clause are not allowed.

See Also:

Aggregate Example

The following example calculates the sum of all salaries in the sample hr.employees table:

SELECT SUM(salary) "Total"

FROM employees;

Total

----------

691400

Analytic Example

The following example calculates, for each manager in the sample table hr.employees, a cumulative total of salaries of employees who answer to that

6-154 Oracle9i SQL Reference