我有两张桌子,我想要"外面"使用SQL连接(然后获取)。确切的SQL查询(有问题)是:
merge(x = data_1, y = data_2, by.x = c("cusip6", "date"), by.y = c("cusip6", "date"), all = T)
这会返回670&293行。
但是当我分别获取两个数据集并且(外部)通过R-merge()连接它们时,我得到1' 182&0 3993行。我使用的两个单独的查询是:
merge(x = data_1, y = data_2, by.x = c("cusip6", "date"), by.y = c("cusip6", "date"))
然后我使用:
合并(外连接)SELECT
p.userid,
p.firstname,
p.lastname,
p.email
FROM
people as p,
employee as emp
WHERE
p.userid = emp.userid
这会返回1' 182&0 3993行,这是正确的。所以我原来的(第一个)SQL查询实际上正在执行一个"内部连接"当我明确指定外连接时。下面的R-merge()返回670和293行,重新验证从SQL获取的数据确实是一个内连接。
PUT http://localhost:9200/indexname
{
"mappings": {
"typename": {
"properties": {
"products" : {
"type" : "nested"
}
}
}
}
}
我的SQL查询出错了什么?
答案 0 :(得分:1)
因为在JOIN之后应用了WHERE子句。此时有NULL值(由于'失败' JOINs),这些行无法通过WHERE子句。
如果您想要一个OUTER JOIN和一个过滤器,请将过滤器放在JOIN或子查询中。
SELECT
LEFT(a.cusip, 6) AS cusip6,
a.date, a.prc, a.ret, a.vol, a.spread, a.shrout,
b.epsf12, (b.seqq-b.pstkq) / b.cshoq AS bps
FROM
(SELECT * FROM crsp.msf WHERE date BETWEEN '2010-01-01' and '2015-12-31') a
FULL JOIN
(SELECT * FROM compa.fundq WHERE datadate BETWEEN '2010-01-01' and '2015-12-31' AND cshoq > 0) b
ON LEFT(a.cusip, 6) = LEFT(b.cusip, 6)
AND a.date = b.datadate