数仓开发需要了解的5大SQL分析函数
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基本语法
analytic_function_name([argument_list])
OVER (
[PARTITION BY partition_expression,…]
[ORDER BY sort_expression, … [ASC|DESC]])
analytic_function_name: 函数名称 — 比如RANK(),SUM(),FIRST()等等partition_expression: 分区列sort_expression: 排序列
案例
数据准备
CREATE TABLE `orders` (
`order_num` String COMMENT '订单号',
`order_amount` DECIMAL ( 12, 2 ) COMMENT '订单金额',
`advance_amount` DECIMAL ( 12, 2 ) COMMENT '预付款',
`order_date` string COMMENT '订单日期',
`cust_code` string COMMENT '客户',
`agent_code` string COMMENT '代理商'
);
INSERT INTO orders VALUES('200100', '1000.00', '600.00', '2020-08-01', 'C00013', 'A003');
INSERT INTO orders VALUES('200110', '3000.00', '500.00', '2020-04-15', 'C00019', 'A010');
INSERT INTO orders VALUES('200107', '4500.00', '900.00', '2020-08-30', 'C00007', 'A010');
INSERT INTO orders VALUES('200112', '2000.00', '400.00', '2020-05-30', 'C00016', 'A007');
INSERT INTO orders VALUES('200113', '4000.00', '600.00', '2020-06-10', 'C00022', 'A002');
INSERT INTO orders VALUES('200102', '2000.00', '300.00', '2020-05-25', 'C00012', 'A012');
INSERT INTO orders VALUES('200114', '3500.00', '2000.00', '2020-08-15', 'C00002','A008');
INSERT INTO orders VALUES('200122', '2500.00', '400.00', '2020-09-16', 'C00003', 'A004');
INSERT INTO orders VALUES('200118', '500.00', '100.00', '2020-07-20', 'C00023', 'A006');
INSERT INTO orders VALUES('200119', '4000.00', '700.00', '2020-09-16', 'C00007', 'A010');
INSERT INTO orders VALUES('200121', '1500.00', '600.00', '2020-09-23', 'C00008', 'A004');
INSERT INTO orders VALUES('200130', '2500.00', '400.00', '2020-07-30', 'C00025', 'A011');
INSERT INTO orders VALUES('200134', '4200.00', '1800.00', '2020-09-25', 'C00004','A005');
INSERT INTO orders VALUES('200108', '4000.00', '600.00', '2020-02-15', 'C00008', 'A004');
INSERT INTO orders VALUES('200103', '1500.00', '700.00', '2020-05-15', 'C00021', 'A005');
INSERT INTO orders VALUES('200105', '2500.00', '500.00', '2020-07-18', 'C00025', 'A011');
INSERT INTO orders VALUES('200109', '3500.00', '800.00', '2020-07-30', 'C00011', 'A010');
INSERT INTO orders VALUES('200101', '3000.00', '1000.00', '2020-07-15', 'C00001','A008');
INSERT INTO orders VALUES('200111', '1000.00', '300.00', '2020-07-10', 'C00020', 'A008');
INSERT INTO orders VALUES('200104', '1500.00', '500.00', '2020-03-13', 'C00006', 'A004');
INSERT INTO orders VALUES('200106', '2500.00', '700.00', '2020-04-20', 'C00005', 'A002');
INSERT INTO orders VALUES('200125', '2000.00', '600.00', '2020-10-01', 'C00018', 'A005');
INSERT INTO orders VALUES('200117', '800.00', '200.00', '2020-10-20', 'C00014', 'A001');
INSERT INTO orders VALUES('200123', '500.00', '100.00', '2020-09-16', 'C00022', 'A002');
INSERT INTO orders VALUES('200120', '500.00', '100.00', '2020-07-20', 'C00009', 'A002');
INSERT INTO orders VALUES('200116', '500.00', '100.00', '2020-07-13', 'C00010', 'A009');
INSERT INTO orders VALUES('200124', '500.00', '100.00', '2020-06-20', 'C00017', 'A007');
INSERT INTO orders VALUES('200126', '500.00', '100.00', '2020-06-24', 'C00022', 'A002');
INSERT INTO orders VALUES('200129', '2500.00', '500.00', '2020-07-20', 'C00024', 'A006');
INSERT INTO orders VALUES('200127', '2500.00', '400.00', '2020-07-20', 'C00015', 'A003');
INSERT INTO orders VALUES('200128', '3500.00', '1500.00', '2020-07-20', 'C00009','A002');
INSERT INTO orders VALUES('200135', '2000.00', '800.00', '2020-09-16', 'C00007', 'A010');
INSERT INTO orders VALUES('200131', '900.00', '150.00', '2020-08-26', 'C00012', 'A012');
INSERT INTO orders VALUES('200133', '1200.00', '400.00', '2020-06-29', 'C00009', 'A002');
AVG() 和SUM()
需求描述：
第三季度每个代理商的移动平均收入和总收入
SELECT
agent_code,
order_date,
AVG( order_amount ) OVER ( PARTITION BY agent_code ORDER BY order_date) avg_rev,
SUM( order_amount ) OVER ( PARTITION BY agent_code ORDER BY order_date ) total_rev
FROM
orders
WHERE
order_date >= '2020-07-01'
AND order_date <= '2020-09-30';
结果输出
A002 2020-07-20 2000 4000
A002 2020-07-20 2000 4000
A002 2020-09-16 1500 4500
A003 2020-07-20 2500 2500
A003 2020-08-01 1750 3500
A004 2020-09-16 2500 2500
A004 2020-09-23 2000 4000
A005 2020-09-25 4200 4200
A006 2020-07-20 1500 3000
A006 2020-07-20 1500 3000
A008 2020-07-10 1000 1000
A008 2020-07-15 2000 4000
A008 2020-08-15 2500 7500
A009 2020-07-13 500 500
A010 2020-07-30 3500 3500
A010 2020-08-30 4000 8000
A010 2020-09-16 3500 14000
A010 2020-09-16 3500 14000
A011 2020-07-18 2500 2500
A011 2020-07-30 2500 5000
A012 2020-08-26 900 900
FIRST_VALUE()和 LAST_VALUE()
- first_value: 取分组内排序后，截止到当前行，第一个值
- last_value: 取分组内排序后，截止到当前行，最后一个值
需求描述
客户首次购买后多少天才进行下一次购买
SELECT
cust_code,
order_date,
datediff(order_date,FIRST_VALUE ( order_date ) OVER ( PARTITION BY cust_code ORDER BY order_date )) next_order_gap
FROM
orders
order by cust_code,next_order_gap
结果输出
C00001 2020-07-15 0
C00002 2020-08-15 0
C00003 2020-09-16 0
C00004 2020-09-25 0
C00005 2020-04-20 0
C00006 2020-03-13 0
C00007 2020-08-30 0
C00007 2020-09-16 17
C00007 2020-09-16 17
C00008 2020-02-15 0
C00008 2020-09-23 221
C00009 2020-06-29 0
C00009 2020-07-20 21
C00009 2020-07-20 21
C00010 2020-07-13 0
C00011 2020-07-30 0
C00012 2020-05-25 0
C00012 2020-08-26 93
C00013 2020-08-01 0
C00014 2020-10-20 0
C00015 2020-07-20 0
C00016 2020-05-30 0
C00017 2020-06-20 0
C00018 2020-10-01 0
C00019 2020-04-15 0
C00020 2020-07-10 0
C00021 2020-05-15 0
C00022 2020-06-10 0
C00022 2020-06-24 14
C00022 2020-09-16 98
C00023 2020-07-20 0
C00024 2020-07-20 0
C00025 2020-07-18 0
C00025 2020-07-30 12
LEAD() 和 LAG()
- lead(value_expr[,offset[,default]])：用于统计窗口内往下第n行值。第一个参数为列名，第二个参数为往下第n行（可选，默认为1），第三个参数为默认值（当往下第n行为NULL时候，取默认值，如不指定，则为NULL
- lag(value_expr[,offset[,default]]): 与lead相反，用于统计窗口内往上第n行值。第一个参数为列名，第二个参数为往上第n行（可选，默认为1），第三个参数为默认值（当往上第n行为NULL时候，取默认值，如不指定，则为NULL）
需求描述
代理商最近一次出售的最高订单金额是多少？
SELECT
agent_code,
order_amount,
LAG ( order_amount, 1 ) OVER ( PARTITION BY agent_code ORDER BY order_amount DESC ) last_highest_amount
FROM
orders
ORDER BY
agent_code,
order_amount DESC;
结果输出
A001 800 NULL
A002 4000 NULL
A002 3500 4000
A002 2500 3500
A002 1200 2500
A002 500 1200
A002 500 500
A002 500 500
A003 2500 NULL
A003 1000 2500
A004 4000 NULL
A004 2500 4000
A004 1500 2500
A004 1500 1500
A005 4200 NULL
A005 2000 4200
A005 1500 2000
A006 2500 NULL
A006 500 2500
A007 2000 NULL
A007 500 2000
A008 3500 NULL
A008 3000 3500
A008 1000 3000
A009 500 NULL
A010 4500 NULL
A010 4000 4500
A010 3500 4000
A010 3000 3500
A010 2000 3000
A011 2500 NULL
A011 2500 2500
A012 2000 NULL
A012 900 2000
RANK() 和DENSE_RANK()
**rank：**对组中的数据进行排名，如果名次相同，则排名也相同，但是下一个名次的排名序号会出现不连续。比如查找具体条件的topN行。RANK() 排序为 (1,2,2,4)
**dense_rank:**dense_rank函数的功能与rank函数类似，dense_rank函数在生成序号时是连续的，而rank函数生成的序号有可能不连续。当出现名次相同时，则排名序号也相同。而下一个排名的序号与上一个排名序号是连续的。
DENSE_RANK() 排序为 (1,2,2,3)
需求描述
每月第二高的订单金额是多少？
SELECT
order_num,
order_date,
order_amount,
order_month
FROM
(
SELECT
order_num,
order_date,
order_amount,
DATE_FORMAT( order_date, 'YYYY-MM' ) AS order_month,
DENSE_RANK ( ) OVER ( PARTITION BY DATE_FORMAT( order_date, 'YYYY-MM' ) ORDER BY order_amount DESC ) order_rank
FROM
orders
) t
WHERE
order_rank = 2
ORDER BY
order_date;
结果输出
200106 2020-04-20 2500 2020-04
200103 2020-05-15 1500 2020-05
200133 2020-06-29 1200 2020-06
200101 2020-07-15 3000 2020-07
200114 2020-08-15 3500 2020-08
200119 2020-09-16 4000 2020-09
200117 2020-10-20 800 2020-10
CUME_DIST()
cume_dist:如果按升序排列，则统计：小于等于当前值的行数/总行数(number of rows ≤ current row)/(total number of rows）。如果是降序排列，则统计：大于等于当前值的行数/总行数。比如，统计小于等于当前工资的人数占总人数的比例 ，用于累计统计。
需求描述
8月和9月每个订单的收入百分比
先查看一下8月和9月的数据，按订单金额排序
SELECT
order_num,
order_amount,
order_date,
agent_code
FROM
orders
WHERE
order_date >= '2020-08-01'
AND order_date <= '2020-09-30'
ORDER BY
date_format( order_date, "YYYY-MM" ),
order_amount;
其结果为：
SELECT
DATE_FORMAT( order_date, 'YYYY-MM' ) AS order_month,
agent_code,
order_amount,
CUME_DIST ( ) OVER ( PARTITION BY DATE_FORMAT( order_date, 'YYYY-MM' ) ORDER BY order_amount )
FROM
orders
WHERE
order_date >= '2020-08-01'
AND order_date <= '2020-09-30';
结果输出
2020-08 A012 900 0.25
2020-08 A003 1000 0.5
2020-08 A008 3500 0.75
2020-08 A010 4500 1.0
2020-09 A002 500 0.16666666666666666
2020-09 A004 1500 0.3333333333333333
2020-09 A010 2000 0.5
2020-09 A004 2500 0.6666666666666666
2020-09 A010 4000 0.8333333333333334
2020-09 A005 4200 1.0
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