Database Developer Interview Preparation Guide
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Database Developer Frequently Asked Questions in various Database Developer job interviews by interviewer. The set of questions are here to ensures that you offer a perfect answer posed to you. So get preparation for your new job interview

70 Database Developer Questions and Answers:

1 :: Please explain what is Database Testing?

It is AKA back-end testing or data testing.
Database testing involves in verifying the integrity of data in the front end with the data present in the back end. It validates the schema, database tables, columns, indexes, stored procedures, triggers, data duplication, orphan records, junk records. It involves in updating records in a database and verifying the same on the front end.

2 :: Explain me what are the different DDL commands in SQL?

DDL commands are used to define or alter the structure of the database.

☛ CREATE: To create databases and database objects
☛ ALTER: To alter existing database objects
☛ DROP: To drop databases and databases objects
☛ TRUNCATE: To remove all records from a table but not its database structure
☛ RENAME: To rename database objects

3 :: Tell us what is a temp table?

A temp table is a temporary storage structure to store the data temporarily.

4 :: Tell me what is a Composite PRIMARY KEY?

Composite PRIMARY KEY is a primary key created on more than one column (combination of multiple fields) in a table.

5 :: Do you know SQL Data Types?

In SQL Server, each column in a database table has a name and a data type. We need to decide what type of data to store inside each and every column of a table while creating a SQL table.

6 :: Tell us what is the difference between Delete, Truncate and Drop command?

The difference between the Delete, Truncate and Drop command is

☛ Delete command is a DML command, it is used to delete rows from a table. It can be rolled back.
☛ Truncate is a DDL command, it is used to delete all the rows from the table and free the space containing the table. It cant be rolled back.
☛ Drop is a DDL command, it removes the complete data along with the table structure(unlike truncate command that removes only the rows). All the tables’ rows, indexes, and privileges will also be removed.

7 :: Tell me what are aggregate functions in SQL?

SQL aggregate functions return a single value, calculated from values in a column. Some of the aggregate functions in SQL are as follows

☛ AVG() – This function returns the average value
☛ COUNT() – This function returns the number of rows
☛ MAX() – This function returns the largest value
☛ MIN() – This function returns the smallest value
☛ ROUND() – This function rounds a numeric field to the number of decimals specified
☛ SUM() – This function returns the sum

8 :: Tell us what do you mean by table and field in SQL?

A table refers to a collection of data in an organised manner in form of rows and columns. A field refers to the number of columns in a table. For example:

Table: StudentInformation
Field: Stu Id, Stu Name, Stu Marks

9 :: Tell me what do you mean by ROWID ?

It’s a 18 character long pseudo column attached with each row of a table.

10 :: Can you explain me what is a Database?

A database is a collection of information in an organized form for faster and better access, storage and manipulation. It can also be defined as a collection of tables, schema, views and other database objects.