Which is fast ? Select * from tableName or Select Column1,Column2 .... From tableName ? and Why ?

Question

Which is fast ? Select * from tableName or Select Column1,Column2 .... From tableName ? and Why ?
select * from Sales.[SalesOrderHeader]
select SalesOrderNumber,RevisionNumber,rowguid from Sales.[SalesOrderHeader]
As you can see both the query execution plan and subtree cost is same. So how selecting the particular columns optimize the query ?

Answer 1

Which is fast ? Select * from tableName or Select Column1,Column2 .... From tableName ? and Why ?
select * from Sales.[SalesOrderHeader]
select SalesOrderNumber,RevisionNumber,rowguid from Sales.[SalesOrderHeader]
As you can see both the query execution plan and subtree cost is same. So how selecting the particular columns optimize the query ?
Yes, selecting specific columns is always better than select *.
If you always need few columns in result, then just use SELECT col1, col2 FROM YourTable. If you SELECT * FROM YourTable; that is extra useless overhead.
If in future if someone adds Image/BLOB/Text type columns in your table, using SELECT * will worsen the performace for sure.
Let's say if you have SP and you use INSERT INTO DestTable SELECT * FROM TABLE which runs fine BUT again if someone adds few more columns then your SP will fail saying provided columns don't match.
-Vaibhav Chaudhari