Question

I have 2 tables I’m trying to join in SQL Server. Table one is a list of salesId‘s and table two is a list of average sales per month by salesId.

Table1 :

SalesId
 0001
 0004
 0345
 1009
 2290
 ....

Table2:

SalesId    AvgMnthSales
 0001       22253.34
 0002        8970.28
 0003       15377.45
 0004         349.03
 0005        3498.44
 ....         ...

So I do a join like this:

Select t1.SalesId, t2.AvgMnthSales
from table1 t1
left join
table2 t2
on t1.SalesId = t2.SalesId

and get something like this:

   SalesId      AvgMnthSales
     0001        22253.34
     0004          349.03
     0345         NULL
     1009         NULL
     2290         8846.56
     ....          ....

What I’d prefer is to have any NULL converted to 0. I’ve seen some examples where this was done in a two step process of sending the results to a temp table and then converting NULL‘s to 0‘s, but was curious if there’s a single step way to do this.

The reason is largely due to ignorance. I’m not sure how temp tables are handled (in RAM or on disk) and how much space they take up as this is a large data set and it would likely take up several GB‘s of RAM or disk space.

Any suggestions would be appreciated.

Answer 1

Select t1.SalesId, COALESCE(t2.AvgMnthSales,0) as AvgMnthSales
from table1 t1
left join
table2 t2
on t1.SalesId = t2.SalesId