如何在具有稀疏日期数的表和另一个具有详尽日期数的表之间进行连接,以使稀疏日期之间的间隙采用上一个稀疏日期的值？
说明性示例:
PRICE table (sparse dates):
date itemid price
2008-12-04 1 $1
2008-12-11 1 $3
2008-12-15 1 $7
VOLUME table (exhaustive dates):
date itemid volume_amt
2008-12-04 1 12345
2008-12-05 1 23456
2008-12-08 1 34567
2008-12-09 1 ...
2008-12-10 1
2008-12-11 1
2008-12-12 1
2008-12-15 1
2008-12-16 1
2008-12-17 1
2008-12-18 1
期望的结果:
date price volume_amt
2008-12-04 $1 12345
2008-12-05 $1 23456
2008-12-08 $1 34567
2008-12-09 $1 ...
2008-12-10 $1
2008-12-11 $3
2008-12-12 $3
2008-12-15 $7
2008-12-16 $7
2008-12-17 $7
2008-12-18 …