05.11 sqlserver over分析函數用法介紹

/***Sql Server*/

/*

OVER ( [ <partition> ]/<partition>

[ <order> ] /<order>

[ ]

)

<partition> ::= PARTITION BY value_expression , ... [ n ] /<partition>

--PARTITION BY將查詢結果集分為多個分區，開窗函數分別應用於每個分區，併為每個分區重新啟動計算；

-- 如果未指定 PARTITION BY，則此函數將查詢結果集的所有行視為單個組。

-- value_expressio：指定行集按其分區的列。value_expression 只能引用可供 FROM 子句使用的列。

-- value_expression 可以是列表達式、標量子查詢、標量函數或用戶定義的變量

<order> ::= ORDER BY order_by_expression [ COLLATE collation_name ] [ ASC | DESC ] [ ,...n ]/<order>

--ORDER BY定義結果集的每個分區中行的邏輯順序。也就是說，它指定按其執行開窗函數計算的邏輯順序。

-- 如果未指定 ROWS/RANGE，但指定了 ORDER BY，則將 RANGE UNBOUNDED PRECEDING AND CURRENT ROW 用作窗口的默認值。

-- order_by_expression指定用於進行排序的列或表達式，只能引用可供 FROM 子句使用的列，不能將整數指定為表示列名或別名。

::= { ROWS | RANGE } <window>

<window> ::= { <window> | <window> }/<window>/<window>/<window>

<window> ::= BETWEEN <window> AND <window>/<window>/<window>

<window> ::= { <window> | <window> }/<window>/<window>/<window>

<window> ::= { UNBOUNDED PRECEDING | <unsigned> PRECEDING | CURRENT ROW }/<unsigned>/<window>

<window> ::= { UNBOUNDED FOLLOWING | <unsigned> FOLLOWING | CURRENT ROW }/<unsigned>/<window>

<unsigned> ::= { <unsigned> }/<unsigned>/<unsigned>

--Range用於指定order by列表中的值與指定的行一致的記錄行，這個指定的行只能是current row(當前行)或unbounded preceding(分區內的第一行) 。

--Rows是用於指定某一行到另外一行之間的所有行，其中的“某一行”和"另外一行"均可以是"n preceding(當前行之前的第n行)"、

-- "n following(當前行之後的第n行)"、"current row(當前行)"、"unbounded preceding(分區內的第一行)"、

-- "unbounded following(分區內的最後一行)"；

-- 但是要求在當前窗口中“某一行”必須排在"另外一行"之前。

-- Rows一般與between...and...同時出現，即“Rows between 某一行 and另外一行”；

-- 但是between..and也可以省略，表示從指定行到當前行之間的行，其中指定行必須為當前行之前的行，

-- 即"unbounded preceding(分區內的第一行)"或"n preceding(當前行之前的第n行)"，比如 Rows unbounded preceding 。

下面是用法舉例：

*/

/*創建測試表*/

create table hptestover

(

v varchar(10),

rn int

);

insert into hptestover(v,rn)values('a',1),('a',2),('a',3);

insert into hptestover(v,rn)values('b',1),('b',2),('b',3);

insert into hptestover(v,rn)values('a',5);

insert into hptestover(v,rn)values('a',4);

/*進行查詢分析：RANGE 只支持使用 UNBOUNDED 和 CURRENT ROW 窗口框架分隔符*/

select v,rn,

sum(rn) over(partition by v order by rn rows between 1 preceding and current row ) row_p1, /*將本行和上一行的rn值相加*/

--sum(rn) over(partition by v order by rn range between 1 preceding and current row ) range_p1, /*將本行和上一行的rn值相加*/

sum(rn) over(partition by v order by rn rows 1 preceding) row_p1_1 , /*將本行和上一行的rn值相加，省略了between，因此，oracle認為結束行時當前行，而開始行為1 precding*/

--sum(rn) over(partition by v order by rn range 1 preceding) range_p1_1 , --將本行和上一行的rn值相加，省略了between，因此，oracle認為結束行時當前行，而開始行為1 precding*/

sum(rn) over(partition by v order by rn rows between current row and 1 following) row_f1, /*將本行和下一行的rn值相加*/

--sum(rn) over(partition by v order by rn range between current row and 1 following) range_f1, /*將本行和下一行的rn值相加*/

sum(rn) over(partition by v order by rn rows between unbounded preceding and current row) row_pn, /*將第一行到當前行的所有rn值相加*/

sum(rn) over(partition by v order by rn range between unbounded preceding and current row) range_pn, /*將第一行到當前行的所有rn值相加*/

sum(rn) over(partition by v order by rn rows unbounded preceding ) row_pn_1, /*將第一行到當前行的所有rn值相加，省略between*/

sum(rn) over(partition by v order by rn range unbounded preceding ) range_pn_1,/*將第一行到當前行的所有rn值相加，省略between*/

sum(rn) over(partition by v order by rn rows between current row and unbounded following) row_fn,/*將當前行到最後一行的所有rn值相加*/

sum(rn) over(partition by v order by rn range between current row and unbounded following) range_fn,/*將當前行到最後一行的所有rn值相加*/

sum(rn) over(partition by v order by rn rows between 1 preceding and 1 following) row_p1_f1, /*將當前行、前一行、最後一行的所有rn值相加*/

--sum(rn) over(partition by v order by rn range between 1 preceding and 1 following) range_p1_f1, /*將當前行、前一行、最後一行的所有rn值相加*/

sum(rn) over(partition by v order by rn rows between unbounded preceding and unbounded following) row_all, /*將所有v值相同的行相加*/

sum(rn) over(partition by v order by rn range between unbounded preceding and unbounded following) range_all, /*將所有v值相同的行相加*/

sum(rn) over(partition by v ) s_all /*將所有v值相同的行相加*/

from hptestover

order by v,rn;

/*清理測試表*/

drop table hptestover;