SAPHANA学习（5）：SQL Function(D)

/*

60.DAYNAME

DAYNAME(<date>)

Returns the weekday in English for the specified date.

DAYOFMONTH(<date>)

Returns an integer for the day of the month for the specified date.

DAYOFYEAR(<date>)

Returns an integer representation of the day of the year for the specified date.

DAYS_BETWEEN(<date_1>, <date_2>)

Computes the number of entire days between <date_1> and <date_2>.

EXTRACT( {YEAR | MONTH | DAY | HOUR | MINUTE | SECOND} FROM <date> )

返回日期部分

*/

SELECT DAYNAME ('2011-05-30') FROM DUMMY;
SELECT DAYOFMONTH ('2011-05-30') FROM DUMMY;
SELECT DAYOFYEAR ('2011-05-30') FROM DUMMY;
SELECT DAYS_BETWEEN (TO_DATE ('2009-12-05', 'YYYY-MM-DD'), TO_DATE('2010-01-05', 'YYYY-MM-DD'))  FROM DUMMY;
SELECT DAYS_BETWEEN('2018-02-07 23:00:00',  '2018-02-08 01:00:00') FROM dummy;
SELECT EXTRACT (YEAR FROM TO_DATE ('2010-01-04', 'YYYY-MM-DD')) FROM DUMMY;

/*

61.RANK

RANK() <window_specification>

Returns rank of a row within a partition, starting from 1.

DENSE_RANK() <window_specification>

Performs the same ranking operation as the RANK function, except that rank numbering does not skip when ties are found.

*/

CREATE ROW TABLE TEST_RANK (class CHAR(10), val INT, offset INT);
INSERT INTO TEST_RANK VALUES('A', 1, 1);
INSERT INTO TEST_RANK VALUES('A', 3, 3);
INSERT INTO TEST_RANK VALUES('A', 5, null);
INSERT INTO TEST_RANK VALUES('A', 5, 2);
INSERT INTO TEST_RANK VALUES('A', 10, 0);
INSERT INTO TEST_RANK VALUES('B', 1, 3);
INSERT INTO TEST_RANK VALUES('B', 1, 1);
INSERT INTO TEST_RANK VALUES('B', 7, 1);

--生成RANK排序值
SELECT
       class,  
       val, 
       ROW_NUMBER() OVER (PARTITION BY class ORDER BY val) AS row_num, 
       RANK() OVER (PARTITION BY class ORDER BY val) AS rank, 
       DENSE_RANK() OVER (PARTITION BY class ORDER BY val) AS dense_rank
     FROM TEST_RANK;

/*

62.DFT

DFT( <expression>, <N> { <series_orderby> | <order_by_clause> } ).{ REAL | IMAGINARY | AMPLITUDE | PHASE }

计算前<N>个值的离散傅里叶变换

参数说明：

<expression>: cannot contain any NULL values.

<N>:This parameter must be a power of 2.

当输入少于<N>个元素，以0填充

series_orderby ：

The SERIES definition can only be used with an equidistant series.

<series_orderby> ::= SERIES( <series_period> <series_equidistant_definition> )

order_by_clause ：

Specifies the sort order of the input rows.

<order_by_clause> ::= ORDER BY <order_by_expression> [, <order_by_expression> [,...] ]

<order_by_expression> ::=

  <column_name> [ <collate_clause> ] [ ASC | DESC ] [ NULLS FIRST | NULLS LAST ]

  | <column_position> [ <collate_clause> ] [ ASC | DESC ] [ NULLS FIRST | NULLS LAST ]

 <collate_clause> ::= COLLATE <collation_name>

*/

SELECT DFT("VALUE",4 ORDER BY "DATE") .REAL FROM CORRELATIONTABLE;
SELECT DFT("VALUE", 8 ORDER BY "DATE").IMAGINARY FROM CORRELATIONTABLE;
SELECT DFT("VALUE", 8 ORDER BY "DATE").AMPLITUDE FROM CORRELATIONTABLE;
SELECT DFT("VALUE", 8 ORDER BY "DATE").PHASE  FROM CORRELATIONTABLE;