RE: explian rowid,rownum?what are the psoducolumns we ...
I would like to add one more point here
Rowid is permanent for the life time whereas rownum is not. What i mean is till the time the record is present in the table the value of ROWID of a particular row in a table will always be same whereas the value of ROWNUM will vary.
RE: explian rowid,rownum?what are the psoducolumns we ...
Rowid is a unique identifier when a row is inserted into the table it generates a row id and will be removed when the row is deleted.
For each row returned by the query a Rownum pseudocolumn is returned in which order oracle selects the rows from the table. Using rownum one can even limit the number of rows selected from the table.
RE: explian rowid,rownum?what are the psoducolumns we have?
Row id: Hexadecimal string representing the unique address of a row in its table. This datatype is primarily for values returned by the ROWID pseudocolumn.
Rownum: For each row returned by a query the ROWNUM pseudocolumn returns a number indicating the order in which Oracle selects the row from a table or set of joined rows. The first row selected has a ROWNUM of 1 the second has 2 and so on. You can use ROWNUM to limit the number of rows returned by a query as in this example:
SELECT * FROM employees WHERE ROWNUM < 10;
A pseudocolumn behaves like a table column but is not actually stored in the table. You can select from pseudocolumns but you cannot insert update or delete their values. This section describes these pseudocolumns:
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