What is a pseudo column in Oracle?
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. A pseudocolumn is also similar to a function without arguments (please refer to Chapter 5, “Functions”.
What are the more common pseudo columns in Oracle?
Pseudocolumn in Oracle SQL
- CURRVAL and NEXTVAL.
- LEVEL.
- ROWID.
- ROWNUM.
What is Oracle pseudo table?
Pseudocolumn: A pseudo-column behaves like a table column but is not actually stored in the table. You can select from pseudo-columns, but you cannot insert, update, or delete their values. A pseudo-column is also similar to a function without arguments.
Is Sysdate a pseudo column?
A pseudo-column is a function which returns a system generated value. sysdate is a function which returns the current datetime; rownum is a pseudo-column that returns the row number in a result set.
Is dual a pseudo column in Oracle?
Dual table is used to select pseudo columns. it has one row and one column DUMMY which has a value X.
WHERE Bfile data will be stored?
Oracle provides Bfile datatypes to store unstructured binary data. The actual data is stored outside the database in the operating system files. A bfile column stores file locator that points to an external file containing data. Bfiles are read-only, one can’t modify them.
Which is not a pseudo column?
SQL and PL/SQL recognizes the following SQL pseudocolumns, which return specific data items: SYSDATE, SYSTIMESTAMP, ROWID, ROWNUM, UID, USER, LEVEL, CURRVAL, NEXTVAL, ORA_ROWSCN, etc. SYSDATE and USER are not pseudo-columns. SYSDATE is a function, so is USER.
What is Nextval?
The Oracle NEXTVAL function is used to retrieve the next value in a sequence. The Oracle NEXTVAL function must be called before calling the CURRVAL function, or an error will be thrown. No current value exists for the sequence until the Oracle NEXVAL function has been called at least once.
What are pseudo records?
They are special as OLD pseudo record holds the column values before start of current transaction and NEW pseudo record holds the column values about to reflect after the transaction completes.