Stop Using select *
Wednesday, August 6th, 2008
In my time trawling through various systems’s DB code, I see we are using “select *” in many places. This has to stop, and we need to specify the columns we want explicitly every time. The reasons for this are:
- A change to the table structure can break the code
- We end up getting all the columns from the DB when we almost certainly don’t need to. Some of the columns can be enormous, and it is a waster of DB and network resource in getting this data.
- A change to the query can add many more columns to be returned.
- It can make a difference to the query plan the DB uses, and can be many orders of magnitude faster to specify columns individually.
Using “select *” is lazy, suboptimal and a coding time bomb.