Question

I have 2 tables

Table Customers:

id,
CustomerName

Table CustomerMapping

ID
WrongName,
CorrectedName

What I want to do is :

Update my TableCustomers.CustomerName with the TableCustomerMapping.CorrectName if TableCustomers.CustomerName = TableCustomerMapping.WrongName

I tried this update statement but it is taking way too long, (6+ minutes) before I give up and cancel the query. I should not be taking that long to update 1000 rows.

Here is the Update statement I was trying, am I missing something?

UPDATE i
SET i.CustomerJob = c.CorrectedName
FROM dbo.TableCustomers i
LEFT JOIN dbo.CustomerMapping c ON (i.CustomerJob = c.WrongName);
GO

Answer 1

If those two tables related by c.CustomerName = m.WrongName.

Also note, there could be more than one person with same wrong name & correct name. Given the situation (not related by IDs) I think following (INNER JOIN or JOIN) will do the job;

--Do this select first for safety
select c.CustomerName, m.CorrectedName
from TableCustomers c join TableCustomerMapping m on c.CustomerName = m.WrongName

--Update if okay
update c
set c.CustomerName = m.CorrectedName
from TableCustomers c join TableCustomerMapping m on c.CustomerName = m.WrongName