SQL PL/SQL Interview Questions 2

6: How could I get distinct entries from a table?
A: The SELECT statement in conjunction with DISTINCT lets you select a set
of distinct values from a table in a database. The values selected from the
database table would of course depend on the various conditions that are
specified in the SQL query. Example
SELECT DISTINCT empname FROM emptable

7: How to get the results of a Query sorted in any order?
A: You can sort the results and return the sorted results to your program
by using ORDER BY keyword thus saving you the pain of carrying out the sorting
yourself. The ORDER BY keyword is used for sorting.
SELECT empname, age, city FROM emptable ORDER BY empname

8: How can I find the total number of records in a table?
A: You could use the COUNT keyword , example
SELECT COUNT(*) FROM emp WHERE age>40

9: What is GROUP BY?
A: The GROUP BY keywords have been added to SQL because aggregate
functions (like SUM) return the aggregate of all column values every time they
are called. Without the GROUP BY functionality, finding the sum for each
individual group of column values was not possible.

10: What is the difference among "dropping a table", "truncating a table"
and "deleting all records" from a table?
A: Dropping : (Table structure + Data are deleted), Invalidates the
dependent objects ,Drops the indexes
Truncating: (Data alone deleted), Performs an automatic commit, Faster than
delete
Delete : (Data alone deleted), Doesn’t perform automatic commit