about Efficiency

[yicong]

I want to select one field from a table,but it should on some conditions
which refer to 5 table ,such as A.FILED1=B.FIELD1 AND B.FIELD2=C.FIELD3 AND
....
Should I use case "select sum(a.amount) from a,b,c,... where
a.field1=b.field1 and b.field2=c.field2 and ..." or "select sum(a.amount)
from select b.field1 from select c.field2 from...."?And which case is more
efficiency?
thanks!

ÎÒÏë¼ÆËãÒ»¸ö±íÖеÄij¸ö×ֶεĺͣ¬µ«´Ë¼Ç¼ÐèÔÚ´Ó¶à¸ö ±íÖвéѯ´Ë¼Ç¼ÊÇ·ñÂú×ãÌض¨µÄÌõ¼þ¡£ÄÇôÎÒÊÇÓÃselect ..from ...where ..and ..and..and ..and ..»¹ÊÇÓÃselect ..from
select ..from select ..from ......£¿ÇëÎÊÊÇÄÄÒ»¸öЧÂʸߣ¿
лл£¡

[Robert Klemme]

On 20.09.2006 10:51, yicong wrote:

I want to select one field from a table,but it should on some conditions
which refer to 5 table ,such as A.FILED1=B.FIELD1 AND B.FIELD2=C.FIELD3 AND
...
Should I use case "select sum(a.amount) from a,b,c,... where
a.field1=b.field1 and b.field2=c.field2 and ..." or "select sum(a.amount)
from select b.field1 from select c.field2 from...."?And which case is more
efficiency?

I cannot make much sense of this. Please rephrase your question and
especially provide more detail (DDL, DML).

A general remark: if you have two equivalent DML statements you can
easily check with MS tools (Profiler, Query Analyzer) which of the two
is more efficient.

Regards

robert

[Ed Murphy]

yicong wrote:

I want to select one field from a table,but it should on some conditions
which refer to 5 table ,such as A.FILED1=B.FIELD1 AND B.FIELD2=C.FIELD3 AND
....
Should I use case "select sum(a.amount) from a,b,c,... where
a.field1=b.field1 and b.field2=c.field2 and ..." or "select sum(a.amount)
from select b.field1 from select c.field2 from...."?And which case is more
efficiency?

select sum(a.amount)
from a
join b on a.field1 = b.field1
join c on b.field2 = c.field2
...