Duplicate data

[oaklander]

I would like to make sure there are no duplicate data entries in my Oracle 9i table (called MainTable) which has an Id field that is the primary key, ValData with a varchar data type, Fid and Fid2 are number data types.

Id   ValData   Fid   Fid2
1    abc         34    2
2    efg          23    34
3    zeo         25    43
 

Sometimes someone can enter a duplicate ValData, Fid and Fid2 and it will end up like this:

Id   ValData   Fid   Fid2
1    abc          34    2
2    efg           23    34
3    zeo          25    43
4    zeo          25    43
 

What constraints or restrictions can I place on the MainTable where it will never allow a duplicate entry into the table?
I would like to do this somehow in the database. If someone tries to enter a duplicate I should get a error message or something to indicate an attempt to enter duplicate data.

Please advise if this is possible?

[amitpatel66]

I would like to make sure there are no duplicate data entries in my Oracle 9i table (called MainTable) which has an Id field that is the primary key, ValData with a varchar data type, Fid and Fid2 are number data types.

Id   ValData   Fid   Fid2
1    abc         34    2
2    efg          23    34
3    zeo         25    43
 

Sometimes someone can enter a duplicate ValData, Fid and Fid2 and it will end up like this:

Id   ValData   Fid   Fid2
1    abc          34    2
2    efg           23    34
3    zeo          25    43
4    zeo          25    43
 

What constraints or restrictions can I place on the MainTable where it will never allow a duplicate entry into the table?
I would like to do this somehow in the database. If someone tries to enter a duplicate I should get a error message or something to indicate an attempt to enter duplicate data.

Please advise if this is possible?

If you want all the columns to be unique, then create a composite key on the table.

In case if you want to allow NULL values, then create a UNIQUE key on other three columns so that it will accept null values also!!