Introduction to Oracle9i: SQL (14)

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##CONTINUE##

• If subqueries are nested to more than 6 levels the performance level generally comes down. So usage of cursors is recommended under these circumstances.
• BACKUP ANY TABLE system privilege may be granted to a role.
• SELECT part_id_seq.NEXTVAL FROM SYS.DUAL;
• The size of a table does not need to be specified.
• System privileges :
  - Creating new users
  - Removing users
  - CREATE TABLE
  - Removing tables
  - Backing up tables
  - CREATE SESSION
  - CREATE SEQUENCE
  - CREATE VIEW
  - CREATE PROCEDURE
  - GRANT
• Object Privilege
  - UPDATE EXECUTE
  - DELETE INDEX
  - INSERT REFERENCES
  - SELECT ALTER
• VARCHAR2 is the only datatype that is variable in length. When creating a column with a VARCHAR2 datatype a length must be specified. CHAR default length of 1 is used.
• Dual is a Dummy table which resides in ‘SYS’ Schema. It has only one column and one row. By Default, all users have privileges to access this table.