Interested to Buy Any Domain ? << Click Here >> for more details...
What is the difference between primary key & unique index ?
- 6 Answers
- 27257 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 |
This was related to -811 sqlcode, In a COBOL DB2 program which accesses employee table and selects rows for employee 'A', it should perform a paragraph s001-x if employee 'A' is present. In this case it gets -811 sqlcode, but still it process the paragraph s001-x. What could be wrong in my code.
Why do we need reorg in db2?
how to u check the query is executing or not ?where will u check for sqlcode ?
What is a page in db2?
I have 3 cursors declared. Cursor1 retieves some data. Based on this curso2 will also fetches some data. In cursor3 (using for some updation) I'm using the data retrieved by the above 2 cursor. My question is, while working with cursor3, periodically if I give commit, will all the three crsors will be closed or only cursor3 will be closed?
For a db2 column that is being defined as decimal (11, 2), discuss the cobol picture clause.
If we keep the DCLGEN structure for a table in a copybook and include it in the COBOL program using the COPY statement, will there be any impact during compilation or at any stage of program execution?
What's the maximum number of volumes that can be added to a STOGROUP?
Name the different types of Table spaces.
How would the varchar column remarks defined?
quary for 1> fetch last record 2> fetch in reverse order 3> fetch last 5 row 4> fetch second last record (their is no primary key) i think concept of count can be use for this in 4th
What is the physical storage length of time data type?
COBOL 
