Oracle developers

Sonata interview questions: what is DBMS_scheduler jobs. collection variables bind variable function vs procedure view vs mview what is trigger? what are type of triggers? sql loader what is difference between conventional path vs direct path? difference between correlated subquery and nested subquery ? with clause?

pseudo columns: 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 and delete their values. pseudo columns are Rowid Rownum currval nextval ORA_ROWSCN Object_id ROWID :                 For each row in the database the rowid returns the address of the row. ROWNUM:                 Rownum returns sequence numbers when used in select statement. ORA_ROWSCN:                 For each row ora_rowscn returns the conservative upper bound system change number (SCN) of the most recent change the row.                          this is useful for determining approximately when a row was last updated.

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