sql语法之over用法（sql overlay）

/***Sql Server*/

/*

OVER ( [ <PARTITION BY clause> ]

[ <ORDER BY clause> ]

[ <ROW or RANGE clause> ]

)

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

--PARTITION BY将查询结果集分为多个分区，开窗函数分别应用于每个分区，并为每个分区重新启动计算；

-- 如果未指定 PARTITION BY，则此函数将查询结果集的所有行视为单个组。

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

-- value_expression 可以是列表达式、标量子查询、标量函数或用户定义的变量

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

--ORDER BY定义结果集的每个分区中行的逻辑顺序。也就是说，它指定按其执行开窗函数计算的逻辑顺序。

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

-- order_by_expression指定用于进行排序的列或表达式，只能引用可供 FROM 子句使用的列，不能将整数指定为表示列名或别名。

<ROW or RANGE clause> ::= { ROWS | RANGE } <window frame extent>

<window frame extent> ::= { <window frame preceding> | <window frame between> }

<window frame between> ::= BETWEEN <window frame bound> AND <window frame bound>

<window frame bound> ::= { <window frame preceding> | <window frame following> }

<window frame preceding> ::= { UNBOUNDED PRECEDING | <unsigned_value_specification> PRECEDING | CURRENT ROW }

<window frame following> ::= { UNBOUNDED FOLLOWING | <unsigned_value_specification> FOLLOWING | CURRENT ROW }

<unsigned value specification> ::= { <unsigned integer literal> }

--Range用于指定order by列表中的值与指定的行一致的记录行，这个指定的行只能是current row(当前行)或unbounded preceding(分区内的第一行) 。

--Rows是用于指定某一行到另外一行之间的所有行，其中的“某一行”和"另外一行"均可以是"n preceding(当前行之前的第n行)"、

-- "n following(当前行之后的第n行)"、"current row(当前行)"、"unbounded preceding(分区内的第一行)"、

-- "unbounded following(分区内的最后一行)"；

-- 但是要求在当前窗口中“某一行”必须排在"另外一行"之前。

-- Rows一般与between...and...同时出现，即“Rows between 某一行 and另外一行”；

-- 但是between..and也可以省略，表示从指定行到当前行之间的行，其中指定行必须为当前行之前的行，

-- 即"unbounded preceding(分区内的第一行)"或"n preceding(当前行之前的第n行)"，比如 Rows unbounded preceding 。

*/

/*创建测试表*/

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);

/*进行查询分析：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, /*将本行和上一行的rn值相加*/

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

sum(rn) over(partition by v order by rn rows 1 preceding) row_p1_1 , /*将本行和上一行的rn值相加，省略了between，因此，oracle认为结束行时当前行，而开始行为1 precding*/

--sum(rn) over(partition by v order by rn range 1 preceding) range_p1_1 , --将本行和上一行的rn值相加，省略了between，因此，oracle认为结束行时当前行，而开始行为1 precding*/

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

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

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

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

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

sum(rn) over(partition by v order by rn range unbounded preceding ) range_pn_1,/*将第一行到当前行的所有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,/*将当前行到最后一行的所有rn值相加*/

sum(rn) over(partition by v order by rn range between current row and unbounded following) range_fn,/*将当前行到最后一行的所有rn值相加*/

sum(rn) over(partition by v order by rn rows between 1 preceding and 1 following) row_p1_f1, /*将当前行、前一行、最后一行的所有rn值相加*/

--sum(rn) over(partition by v order by rn range between 1 preceding and 1 following) range_p1_f1, /*将当前行、前一行、最后一行的所有rn值相加*/

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

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

from hptestover

order by v,rn;

/*清理测试表*/

drop table hptestover;

/***Oracle*/

/* 语法：

over(

[query_partition_clause]

[order by clause]

[windowing clause]

)

<query_partition_clause> ::= parition by expr,...[n]

<order by clause> ::= order[sliblings] by {expr|position|c_alias} [asc|desc] [nulls first|nulls last] [,...n]

<windowing_clause> ::= {rows|range} <window frame extent>

<window frame extent> ::= { <window frame between> | <window frame preceding> }

<window frame between> ::= BETWEEN <window frame bound1> AND <window frame bound2>

--BETWEEN...AND子句为窗口指定开始和结束位置，第一个表达式定义开始位置，第二个表达式定义结束位置，

-- 如果省略了bewteen，oracle会认为结束位置是当前行，而开始位置是表达式指定的行；

<window frame bound1> ::= { UNBOUNDED PRECEDING | CURRENT ROW | value_expr {PRECEDING|FOLLOWING} }

<window frame bound2> ::= { UNBOUNDED FOLLOWING | CURRENT ROW | <value_expr> {PRECEDING|FOLLOWING} }

<window frame preceding> ::= { UNBOUNDED PRECEDING | CURRENT ROW | <value_expr> PRECEDING }

<value_expr> ::= {columns|nonanalytic functions|function expressions|expressions involving any of these}

ROWS和RANGE关键字为每行定义一个窗口(物理或逻辑的行的集合)，用于计算函数的结果，分析函数可以应用到在窗口中的所有行，按自上而下的顺序计算函数值。

ROWS 标识出窗口的物理单元(rows）。 ROWS specifies the window in physical units (rows)

RANGE 通过逻辑偏移量标识出窗口。RANGE specifies the window as a logical offset. 指的是order by的值的差额的范围

-- RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW 可简写为 RANGE UNBOUNDED PRECEDING.

-- RANGE BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING

-- RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW 可简写为 RANGE UNBOUNDED PRECEDING.

-- RANGE BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING

*/

create table hptestover

(

v varchar(10),

v1 int,

rn int

);

insert into hptestover(v,v1,rn)

select 'a',level,level from dual connect by level < 7;

insert into hptestover(v,v1,rn)

select 'b',level*level,level from dual connect by level < 4;

insert into hptestover(v,v1,rn)values('c',1,5);

insert into hptestover(v,v1,rn)values('c',3,6);

insert into hptestover(v,v1,rn)values('c',9,10);

insert into hptestover(v,v1,rn)values('d',1,2);

insert into hptestover(v,v1,rn)values('d',2,4);

insert into hptestover(v,v1,rn)values('d',4,7);

/*RANGE只指定了前后两个值(order by列的值)之间相差值的范围，而ROWS则指定了前后多少行的范围。*/

/*进行查询分析*/

select v,v1,rn,

sum(rn) over(partition by v order by v1 rows between 1 preceding and current row ) row_p1, /*将本行和上一行的rn值相加*/

sum(rn) over(partition by v order by v1 range between 1 preceding and current row ) range_p1, /*将本行之前的rn差额不超过1，本行之后的的rn等于当前行的所有rn值相加*/

sum(rn) over(partition by v order by v1 range between 2 preceding and current row ) range_p2, /*将本行之前的rn差额不超过2，本行之后的的rn等于当前行的所有rn值相加*/

sum(rn) over(partition by v order by v1 rows 1 preceding) row_p1_1 , /*将本行和上一行的rn值相加，省略了between，因此，oracle认为结束行时当前行，而开始行为1 precding*/

sum(rn) over(partition by v order by v1 range 1 preceding) range_p1_1 , /*将本行之前的rn差额不超过1，本行之后的的rn等于当前行的所有rn值相加，省略了between，因此，oracle认为结束行时当前行，而开始行为1 precding*/

sum(rn) over(partition by v order by v1 range 2 preceding) range_p2_1 , /*将本行之前的rn差额不超过2，本行之后的的rn等于当前行的所有rn值相加*/

sum(rn) over(partition by v order by v1 range 4 preceding) range_p4_1 , /*将本行之前的rn差额不超过2，本行之后的的rn等于当前行的所有rn值相加*/

sum(rn) over(partition by v order by v1 rows between current row and 1 following) row_f1, /*将本行和下一行的rn值相加*/

sum(rn) over(partition by v order by v1 range between current row and 1 following) range_f1, /*将本行和下一行的rn值相加*/

sum(rn) over(partition by v order by v1 range between current row and 4 following) range_f4, /*将本行和下一行的rn值相加*/

sum(rn) over(partition by v order by v1 rows between unbounded preceding and current row) row_pn, /*将第一行到当前行的所有rn值相加*/

sum(rn) over(partition by v order by v1 range between unbounded preceding and current row) range_pn, /*将第一行到当前行的所有rn值相加*/

sum(rn) over(partition by v order by v1 rows unbounded preceding ) row_pn_1, /*将第一行到当前行的所有rn值相加，省略between*/

sum(rn) over(partition by v order by v1 range unbounded preceding ) range_pn_1, /*将第一行到当前行的所有rn值相加，省略between*/

sum(rn) over(partition by v order by v1 rows between current row and unbounded following) row_fn, /*将当前行到最后一行的所有rn值相加*/

sum(rn) over(partition by v order by v1 range between current row and unbounded following) range_fn, /*将当前行到最后一行的所有rn值相加*/

sum(rn) over(partition by v order by v1 rows between 1 preceding and 1 following) row_p1_f1, /*将当前行、前一行、最后一行的所有rn值相加*/

sum(rn) over(partition by v order by v1 range between 1 preceding and 1 following) range_p1_f1, /*将当前行、前一行、最后一行的所有rn值相加*/

sum(rn) over(partition by v order by v1 rows between unbounded preceding and unbounded following) row_all, /*将所有v值相同的行相加*/

sum(rn) over(partition by v order by v1 range between unbounded preceding and unbounded following) range_all, /*将所有v值相同的行相加*/

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

from hptestover

order by v,v1;

--清理测试表

drop table hptestover;