DECOMPOSE

See Also:

■"Datatype Comparison Rules" on page 2-45 for information on comparison semantics

■"Data Conversion" on page 2-48 for information on datatype conversion in general

■"Implicit and Explicit Data Conversion" on page 2-49 for information on the drawbacks of implicit conversion

Examples

This example decodes the value warehouse_id. If warehouse_id is 1, then the function returns ’Southlake’; if warehouse_id is 2, then it returns ’San Francisco’; and so forth. If warehouse_id is not 1, 2, 3, or 4, then the function returns ’Non-domestic’.

SELECT product_id,

DECODE (warehouse_id, 1, ’Southlake’,

2, ’San Francisco’, 3, ’New Jersey’,

4, ’Seattle’, ’Non-domestic’)

"Location of inventory" FROM inventories WHERE product_id < 1775;

DECOMPOSE

Syntax decompose::=

Purpose

DECOMPOSE is valid only for Unicode characters. DECOMPOSE takes as its argument a string in any datatype and returns a Unicode string after decomposition in the same character set as the input. For example, an o-umlaut codepoint will be returned as the "o" codepoint followed by an umlaut codepoint.

Functions 6-53

DECOMPOSE

■string can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2,

CLOB, or NCLOB.

■CANONICAL causes canonical decomposition, which allows recomposition (for example, with the COMPOSE function) to the original string. This is the default.

■COMPATIBILITY causes decomposition in compatibility mode. In this mode, recomposition is not possible. This mode is useful, for example, when decomposing half-width and full-width katakana characters, where recomposition might not be desirable without external formatting or style information.

See Also: Oracle9i Database Concepts for information on Unicode character sets and character semantics

Examples

The following example decomposes the string "Châteaux" into its component codepoints:

SELECT DECOMPOSE (’Châteaux’) FROM DUAL;

DECOMPOSE

---------

Cha^teaux

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DENSE_RANK

DENSE_RANK

Aggregate Syntax dense_rank_aggregate::=

Analytic Syntax dense_rank_analytic::=

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

Purpose

DENSE_RANK computes the rank of a row in an ordered group of rows. The ranks are consecutive integers beginning with 1. The largest rank value is the number of unique values returned by the query. Rank values are not skipped in the event of ties. Rows with equal values for the ranking criteria receive the same rank.

■As an aggregate function, DENSE_RANK calculates the dense rank of a hypothetical row identified by the arguments of the function with respect to a given sort specification. The arguments of the function must all evaluate to constant expressions within each aggregate group, because they identify a single row within each group. The constant argument expressions and the expressions in the order_by_clause of the aggregate match by position. Therefore, the number of arguments must be the same and types must be compatible.

Functions 6-55

DENSE_RANK

■As an analytic function, DENSE_RANK computes the rank of each row returned from a query with respect to the other rows, based on the values of the value_ exprs in the order_by_clause.

Aggregate Example

The following example computes the ranking of a hypothetical employee with the salary $15,500 and a commission of 5% in the sample table oe.employees:

SELECT DENSE_RANK(15500, .05) WITHIN GROUP

(ORDER BY salary DESC, commission_pct) "Dense Rank" FROM employees;

Dense Rank

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

3

Analytic Example

The following statement selects the department name, employee name, and salary of all employees who work in the HUMAN RESOURCES or PURCHASING department, and then computes a rank for each unique salary in each of the two departments.

The salaries that are equal receive the same rank. Compare this example with the example for RANK on page 6-123.

SELECT d.department_name, e.last_name, e.salary, DENSE_RANK() OVER (PARTITION BY e.department_id ORDER BY e.salary) as drank FROM employees e, departments d

WHERE e.department_id = d.department_id AND d.department_id IN (’30’, ’40’);

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