Interested to Buy Any Domain ? << Click Here >> for more details...
What is the difference between primary key & unique index ?
- 6 Answers
- 27072 Views
- Patni, Temenos, I also Faced
- E-Mail Answers
Answers were Sorted based on User's Feedback
Answer / shankar
Primary Key cannot have NULL values in it wherein an
UNIQUE index can have one NULL value in it.
| Is This Answer Correct ? | 37 Yes | 3 No |
Answer / mani
Primary key can be defined only one for a table whereas
number of unique indexes can be defined for a table.
primary key can not have null values but unique can have
null values and to remind one null value can never be equal
to another null value.
| Is This Answer Correct ? | 23 Yes | 4 No |
Answer / uddipto banerji
1. Primary Key is a column or a set of columns that uniquely identifies a row.Its purpose RECORD UNIQUENESS
2. Primary Key will not allow duplicate values.
3. Primary Key will not allow null.
4. Primary Key is not compulsory but recommended.
5. Primary Key helps to identify one record from another.
6. Only One Primary Key is allowed per table.
7. Unique Indexes is created automatically if there is Primary Key.
8. One table can combine upto 16 columns in a Composite Primary Key.
9. A table can have more than one Unique Key which is not possible in a Primary Key.
| Is This Answer Correct ? | 10 Yes | 2 No |
Answer / palash ghosh
1)Primary key creates an implicit culstered index on a
table, unique key does not create any implicit index.
2)Columns defined as primary key does not allow null values,
where as columns defined as unique can allow null values.
3)A table can have just one primary key (can be a composite
key) where as there can be multiple unique columns (keys).
4)Primary key is a unique key with the above mentioned
features.
| Is This Answer Correct ? | 9 Yes | 1 No |
Answer / mehdee
- Each primary key must associate with a unique index, but
unique index dose not have to associate to the primary key.
| Is This Answer Correct ? | 6 Yes | 3 No |
Answer / s
Primary Key uniquely identifies the record and the UNIQUE
index on the primary key ensures that no duplicates values
will be stored in the table.
| Is This Answer Correct ? | 16 Yes | 14 No |
What is the use of DELGEN in DB2? Can we Write the program with out using it?
What is a Resource Control Table(RCT)? Describe its characteristics.
What is scrollable cursor in db2?
What will happen, while trying to close the closed cursor.
What is lock escalation?
For update of a row in cursors, when do we move value into host variable in cobol progrm? is it before open or before fetch ?
How can tablespace be moved to another dasd volume that is allocated for that tablespace?
How many databases are there?
What is cobol db2?
What is the command used by TSO users to invoke DB2?
Hi i need to write a query on the following requirement. SELECT COMM_TEXT INTO :WS_MIKM_COMM_TEXT FROM MPIPROD.MIKMV01 WHERE ACCOUNT_NO = :WFD_ACCOUNT_NO AND (SUBSTR(COMM_TEXT,1,39) = :WS_COMMENT_TEXT AND SUBSTR(COMM_TEXT,47,14) = :WS_DENY_DESC) OR (SUBSTR(COMM_TEXT,1,39) = :WS_COMMENT_TEXT) The above query is to be modified. The requirement is if both the fields are equal then that has to be given priority. In the above query if it satisfies any one it comes out without checking if both being equal is possible.
Explain the use of the WHERE clause.
COBOL 
