Oracle认证：oracle中的DDL、DML、DCL

会计考友

DDL 　　Data Definition Language (DDL) statements are used to define the database structure or schema. Some examples:
　　CREATE - to create objects in the database
3 O' m$ n( V) @8 N# h8 j) _% C　　ALTER - alters the structure of the database
　　DROP - delete objects from the database
　　TRUNCATE - remove all records from a table, including all spaces allocated for the records are removed
2 i4 ~2 |3 I& f5 O8 @5 _7 g　　COMMENT - add comments to the data dictionary
　　RENAME - rename an object
- ?8 f% u. _2 s　　DML
　　Data Manipulation Language (DML) statements are used for managing data within schema objects. Some examples:
　　SELECT - retrieve data from the a database
　　INSERT - insert data into a table
4 t9 l2 E/ W4 ?9 t1 Z　　UPDATE - updates existing data within a table
# {9 T3 U, v- D/ J; I. ^2 j$ G0 {8 F　　DELETE - deletes all records from a table, the space for the records remain
　　MERGE - UPSERT operation (insert or update)
5 r; |' G1 N+ p5 C1 G% h' X　　CALL - call a PL/SQL or Java subprogram
; C* L, ^8 \9 k# o7 U0 ~9 Y" H　　EXPLAIN PLAN - explain access path to data
　　LOCK TABLE - control concurrency
　　DCL
　　Data Control Language (DCL) statements. Some examples:
$ R8 B7 S. ^2 _8 y, p0 |; a　　GRANT - gives user's access privileges to database
　　REVOKE - withdraw access privileges given with the GRANT command
　　TCL
　　Transaction Control (TCL) statements are used to manage the changes made by DML statements. It allows statements to be grouped together into logical transactions.
　　COMMIT - save work done
　　SAVEPOINT - identify a point in a transaction to which you can later roll back
" u5 b" [" i7 W# T& y' O　　ROLLBACK - restore database to original since the last COMMIT
* r/ z# p! t9 r$ e; l* D; a　　SET TRANSACTION - Change transaction options like isolation level and what rollback segment to use