oracle语法（oracle语法）.docVIP

oracle语法（oracle语法） Basic concepts DDL data definition language - building database objects Create /alter/ drop/ truncate DML data manipulation language - data view and maintenance Select / insert /delete /update TCL transaction control language - whether data is saved to the database Commit / rollback / savepoint DCL data control language -- view the permissions of objects Grant / revoke Database design Composition of relational data model One or more sheets Table index view trigger The relation between table and table Database Schema Conceptually: a group of DDL Physical: a namespace that contains tables, processes, views collections Common commands Connect username / password connected to the specified user The structure of desc tab_name view table tab_name Quit/exit exit Clear screen clear screen Set linesize 200 sets one line and displays 200 characters Set PageSize 20 sets 20 lines per page Dbms_output.put_line () print, similar to System.out.println (); Set serveroutput on opens the server output, otherwise the above print statement is wrong Edit edits the statements in the cache Execute the last statement block / repeatable execution @ sqlpath executes a SQL file @ @ sqlfile implementation of the sqlpath environment variable file Spool file print log to text file Spool off stop printing In the process of # enter the SQL statement in the temporary first run a sql*plus command Look at the size of the short characters SELECT DBMS_LOB.GETLENGTH (MYCLOB) FROM ATTACHMENT; //MYCLOB is column name, and ATTACHMENT is table name SELECT DBMS_LOB.GETLENGTH (MYBLOB) FROM ATTACHMENT; Common tables User_constraints user constraints User_tables user table All_all_tables all user tables All_constraints all constraints User_cons_columns constraint column All_cons_columns all constraint columns Nls_session_parameters current session information V$nls_parameters system parameters data type Character Char maximum 2000 bytes fixed length VARCHAR2 maximum 4000 bytes longer Numeric