尝试连接两个表，将空字段显示为额外行，并将这些空值设为0

Question

所以我有两张桌子。

select distinct id, doc
from images

看起来像：

 ID     |   DOC
--------------------
GROWG       APP
GROWG       BACKGR
MAXAR       APP
MAXAR       BACKGR
MAXAR       LIC

和

select DriverID
from drivers

看起来像

DriverID
--------
GROWG
ZULLY
MAXAR
JILLX

当我使用临时表或select语句时，我希望我的最终结果看起来像是这样：

DriverID     |     Doc     |     Count
-----------------------------------------
GROWG              APP             1
GROWG              BACKGR          1
GROWG              LIC            **NULL** (or 0)
MAXAR              APP             1
MAXAR              BACKGR          1
MAXAR              LIC             1

所以最后它认识到总共有3种不同类型的文件，它表明GROWG错过了他的文件＆＃34; LIC＆＃34;

有人可以帮忙吗？

Answer 1

我想你想要这样的东西：

select id.id, doc.doc, count(i.id) as cnt
from (select distinct id from images) as id cross join
     (select distinct doc from images) doc left outer join
     images i
     on i.id = id.id and i.doc = doc.doc;

它会返回id中doc和images的所有组合以及表格的计数。如果组合不存在，则返回0。

编辑：

要检查与drivers的匹配，您只需添加：

where id in (select driverid from drivers)

Answer 2

我已经从Gordon Linoff修改了上述查询。检查一下

 select id.driverid, doc.doc, count(i.id) as cnt
from (select distinct driverid from drivers) as id cross join
     (select distinct doc from images) doc left outer join
     images i
     on i.id = id.driverid and i.doc = doc.doc 
     where id.driverid in (select id from images )
     group by id.driverid,doc.doc;