This set of interview questions for Junior Database Administrators (DBA) help you evaluate candidates' skills and qualifications to make more informed hiring decisions.
Interview questions for Junior Database Administrators (DBA)
What is the maximum number of clustered indexes a table can have?
Can you tell what types of outer joins exist in SQL Server 2016?
Answer: LEFT, RIGHT, FULL
What types of table or column constraints we have?
Answer: NOT NULL, PRIMARY KEY, FOREIGN KEY, UNIQUE, CHECK
If we create many non-clustered indexes on a table, what operations are likely to be considerably slower than before?
Answer: Write operations (INSERT, UPDATE, DELETE, MERGE)
The choice of a clustering key columns of a clustered index is crucial for performance. Name at least two characteristics that a good clustering key should have.
Answer: UNIQUE, SLIM SIZE (small width in bytes), EVER INCREASING, fixed width, not null
When we talk about non-clustered index, how many KEY columns can it have and how many INCLUDED columns?
Answer: 16 key columns and unlimited include columns (all table columns can be included). Answering 1 is really bad. Answer between 2-15 is not that bad. 16 is correct.
In a trigger that fires after UPDATE of a table, what are the names of the metatables we can access within a trigger code to check which rows were updated?
Answer: INSERTED, DELETED
When users complain about performance, what is the name of the procedure you can use to quickly list the current sessions and see what are they doing or waiting for?
Answer: sp_who2 or sp_WhoIsActive (one is enough)
What DMV stands for?
Answer: Dynamic Management View
What types of a backup do we need, if we want to restore to a point in time?
Answer: FULL, LOG, and optionally DIFFERENTIAL