WINDOW FUNCTION LAG
description
LAG() 方法用来计算当前行向前数若干行的值。
LAG(expr, offset, default) OVER (partition_by_clause order_by_clause)example
计算前一天的收盘价
select stock_symbol, closing_date, closing_price,
lag(closing_price,1, 0) over (partition by stock_symbol order by closing_date) as "yesterday closing"
from stock_ticker
order by closing_date;
| stock_symbol | closing_date | closing_price | yesterday closing |
|--------------|---------------------|---------------|-------------------|
| JDR | 2014-09-13 00:00:00 | 12.86 | 0 |
| JDR | 2014-09-14 00:00:00 | 12.89 | 12.86 |
| JDR | 2014-09-15 00:00:00 | 12.94 | 12.89 |
| JDR | 2014-09-16 00:00:00 | 12.55 | 12.94 |
| JDR | 2014-09-17 00:00:00 | 14.03 | 12.55 |
| JDR | 2014-09-18 00:00:00 | 14.75 | 14.03 |
| JDR | 2014-09-19 00:00:00 | 13.98 | 14.75 |keywords
WINDOW,FUNCTION,LAG