WINDOW FUNCTION LEAD
description
LEAD() 方法用来计算当前行向后数若干行的值。
LEAD(expr, offset, default]) OVER (partition_by_clause order_by_clause)example
计算第二天的收盘价对比当天收盘价的走势，即第二天收盘价比当天高还是低。
select stock_symbol, closing_date, closing_price,
case
(lead(closing_price,1, 0)
over (partition by stock_symbol order by closing_date)-closing_price) > 0
when true then "higher"
when false then "flat or lower"
end as "trending"
from stock_ticker
order by closing_date;
| stock_symbol | closing_date | closing_price | trending |
|--------------|---------------------|---------------|---------------|
| JDR | 2014-09-13 00:00:00 | 12.86 | higher |
| JDR | 2014-09-14 00:00:00 | 12.89 | higher |
| JDR | 2014-09-15 00:00:00 | 12.94 | flat or lower |
| JDR | 2014-09-16 00:00:00 | 12.55 | higher |
| JDR | 2014-09-17 00:00:00 | 14.03 | higher |
| JDR | 2014-09-18 00:00:00 | 14.75 | flat or lower |
| JDR | 2014-09-19 00:00:00 | 13.98 | flat or lower |keywords
WINDOW,FUNCTION,LEAD