SQL Interview Questions

19 flashcards · Other · by Moses John Prakash

1. WHAT IS A DATABASE

   ORGANISED COLLECTION OF INTER RELATED DATA.

2. WHAT IS A PRIMARY KEY

   UNIQUELY IDENTIFIES THE RECORDS IN THE TABLE.

3. WHAT IS DDL

   DATA DEFINITION LANGUAGE

4. WHAT ARE THE KEYWORDS UNDER DDL

   CREATE, ALTER, RENAME, TRUNCATE, DROP

5. WHAT IS DML

   DATA MANIPLUATION LANGUAGE

6. WHAT ARE THE KEYWORDS UNDER DML

   INSERT, UPDATE, DELETE, SELECT

7. WHAT IS DBMS

   IT IS A SOFTWARE APPLICATION THAT IS USED TO MANAGE DATA IN THE DATABASE. IT INTERACTS WITH THE USER, APPLICATION AND THE DATABASE TO CAPTURE AND ANALYSE DATA .

8. WHAT IS TCL

   TRANSACTION CONTROL LANGUAGE

9. WHAT IS COMMIT

   COMMAND USED TO SAVE THE CHANGES

10. WHAT ARE THE TWO MAJOR TYPES OF DBMS

    RELATIONAL DATABASE and 2. NON RELATIONAL DATABASE.

11. WHAT IS NULL VALUE

    UNKNOWN VALUE OR UNASSIGNED VALUE.

12. WHAT ARE THE SUBSETS OF SQL

    DDL, DML, TCL AND DCL

13. WHAT IS THE DIFFERENCE BETWEEN DELETE AND TRUNCATE

    DELETE is used to delete one or more records / rows in a table. it can be rolled back and will not release space. TRUNCATE is used to delete all the records from the table> It cannot be rolled back but it will release the space.

14. WHAT IS THE DIFFERENCE BETWEEN CHAR AND VARCHAR()

    CHAR IS FIXED LENGTH CHARACTER DATA WHILE VARCHAR IS VARIABLE LENGTH CHARACTER DATA.

15. WHAT ARE SET OPERATORS

    Used to combine results from two or more select statements on to a single result.

16. WHAT IS THE DIFFERENCE BETWEEN SET OPERATOR AND AND JOIN

    SQL JOINS are used to combine columns whereas SET OPERATORS are used to join rows from multiple SELECT queries.

17. WHAT ARE INDEXES

    Indexes are special database objects used to improve the query performance.

18. WHICH KEYWORD IS USED TO ELIMINATE DUPLICATE VALUES

    DISTINCT

19. WHAT IS A GROUP FUNCTION OR AGGREGATE FUNCTION

    Group functions act GROUP OR SET OF ROWS and return ONE RESULT per group.