SQL INTERVIEW QUESTION & ANSWERS
| 16. |
What are the different types of database schemas? |
| |
- Physical schema : It describes the database design at the physical level.
- Logical schema : It describes the database design at the logical level
- Subschema : A database may also have several subschemas at the view level, called as subschemas.
|
| 17. |
What are the drawbacks of file processing system? |
| |
The drawbacks of file processing system are : - Duplication of data, which leads to wastage of storage space and data inconsistency.
- Separation and isolation of data, because of which data cannot be used
together.
- No program data independence.
|
| 18. |
What is meant by Physical and Logical data independence? |
| |
In logical data independence, the conceptual schema can be changed without
changing the external schema. In physical data independence, the internal schema can be changed without changing the conceptual schema. |
| 19. |
What are the types of data manipulation languages? |
| |
There are two types of DMLs are : - Procedural DMLs
- Declarative DMLs
|
| 20. |
What are the differences between the first normal form and the second normal form? |
| |
According to the first normal form, each attribute of a tuple must contain only one value, each tuple in a relation must contain the same number of values, and each tuple in a relation must be different. According to the second normal form, a relation must be in first normal form and all attributes in a
relation must be dependent on the entire candidate key. |
