Set - 6

Question 61 :

What is a join ? Explain the different types of joins ?

Answer :

Join is a query which retrieves related columns or rows from multiple tables.Self Join - Joining the table with itself.Equi Join - Joining two tables by equating two common columns.Non-Equi Join - Joining two tables by equating two common columns.Outer Join - Joining two tables in such a way that query can also retrieve rows that do not have corresponding join value in the other table.


Question 62 :

If an unique key constraint on DATE column is created, will it validate the rows that are inserted with SYSDATE ?

Answer :

It won't, Because SYSDATE format contains time attached with it.


Question 63 :

How does one stop and start the OMS? (for DBA)

Answer :

Use the following command sequence to stop and start the OMS (Oracle Management Server):
oemctl start oms
oemctl status oms sysman/oem_temp
oemctl stop oms sysman/oem_temp
Windows NT/2000 users can just stop and start the required services. The default OEM administrator is "sysman" with a password of "oem_temp".
NOTE: Use command oemctrl instead of oemctl for Oracle 8i and below.


Question 64 :

What is an Integrity Constraint ?

Answer :

Integrity constraint is a rule that restricts values to a column in a table.


Question 65 :

How does one create a repository? (for DBA)

Answer :

For OEM v2 and above, start the Oracle Enterprise Manager Configuration Assistant (emca on Unix) to create and configure the management server and repository. Remember to setup a backup for the repository database after creating it.