HOW TO ENTER SQL AND SQL*PLUS STATEMENTS?

How to enter SQL statements? :

SQL*PLUS allow to types of command to entered at the prompt - SQL and SQL*PLUS. SQL commands include commands of ANSI/ISO SQL and extra commands added to ANSI SQL by oracle. The following are the rules to be followed while entering SQL commands.

• An SQL statement may be entered in multiple lines.
• It is not possible to break a word across lines. 
• 
  
• SQL statement must be terminated by semicolon (;). 

The following is an example of SQL command. 

What this command does is not important at this moment.
In the above command, we entered the command in three lines. When you enter semicolon and press enter key then SQL*PLUS will take it as the end of the command. Also note that you have to press enter key at the end of each line.

How to enter SQL*PLUS statements?   : SQL*Plus statements are available only in SQL*PLUS. They are not part of standard SQL. SQL*Plus commands are mainly used for two purposes – editing SQL commands and formatting result of query.

The following rules are to be followed while entering these commands. :

• The entire command must be entered on a single line.
• No need to terminate command with semicolon (;). 
• Commands can be abbreviated. However, the amount of abbreviation is not fixed. Some commands are abbreviated to one letter some are abbreviated to 2 and so on.

Common Errors :The following are the common errors that you get while you are trying to log on to Oracle.

  

Ora-01017: invalid username/password; login denied 

The reason for this error is that you have entered a username or password that is not valid. Check whether username you are entering is really existing and password is correctly typed. Sql*plus gives you three chances to type username and password correctly. If you cannot log on successfully in three chances then Sql*plus will exit. However, you can restart Sql*plus again.

ORA-01034: ORACLE not available : The reason for this message is that Oracle Instance is not up and running. You have to first make sure you have started Oracle Instance. Actually there are a few other problems that occurs when Oracle Instance has not started successfully. If this is case in Oracle Server, notify administrator. If this is the case with Personal Oracle, make sure you start database as mentioned in “starting up database” section.