Learn about Oracle and learn how to get started

Learn about Oracle and learn how to get started

Unable to log on upon login: No listener program --- start service OracleXETNListener listener unable to identify request service in connection description ---- Restart service OracleServiceXE check host value of tnsnames. ora

When PL/SQL is not installed: Run sqlplus to log on, and view all Oracle users in the user_tables table: end with a statement.

Oracle Data Type: character data type: char, varchar2, nchar, nvarchar2 numeric data type: number date and Time data type: date, timestamp LOB data type: blob, clob, bfile ** varchar, integer, float, double, and Other types are not recommended.

Pseudo column: rowid: identifies the data in the database rownum: commonly used for writing Paging

-- Paging Query
-- (PageNo-1) * pagesize = start row pageNo * pagesize = end row

Select * from (
Select rownum rm, s. * from (
Select * from myfirsttb order by stuage desc) s where rownum <= 5) where rm> = 1;

Experience: After adding or deleting a modification statement in oracle, you must submit the transaction to take effect before committing or rolling back: commit/rollback