如何添加新列并从其他列获取数据？ SQL

Question

You can see what I exactly mean on the image below. I want to create new column " Bill To This Company " and get the company name from BillToCustomerID

Answer 1

Could be you need a self join

select a.customerId, a.CustomerName, a.BillToCustomerId, b.CustmerName 
from my_table a 
inner join my_table  b on a.BillToCustomerId = b.customerId

Answer 2

Just self-join on the table and give that CustomerName an alias

select 
 c.CustomerId, 
 c.CustomerName, 
 c.BillToCustomerId, 
 b.CustomerName as "Bill To This Company"
from Customer c
left join Customer b on (b.CustomerId = c.BillToCustomerId)

Answer 3

Seems you need subquery :

select c.*,
       (select c1.CustomerName
        from Customer c1
        where c1.BillToCustomerId = c.BillToCustomerId
        order by c1.customerid 
        limit 1
       ) as BilltoThisCompany
from Customer c;

Answer 4

update tableName as t1 join tableName as t2 on t1.BillToCustomerID=t2.CustomerId
  set t1.`Bill To This Company` = t2.customerName;