A Using SQL Command Line
This section provides an introduction to SQL Command Line (SQL*Plus), an interactive and batch command-line query tool that is installed with Oracle Database Express Edition.
This section contains the following topics:
For information about running SQL language statements, see Chapter 3, “Using SQL”.
Oracle Database SQL Reference for information about using SQL statements
Oracle Database Express Edition 2 Day DBA for information about connecting to Oracle Database XE with SQL Command Line
Overview of SQL Command Line
SQL Command Line (SQL*Plus) is a command-line tool for accessing Oracle Database XE. It enables you to enter and run SQL, PL/SQL, and SQL*Plus commands and statements to:
Query, insert, and update data
Execute PL/SQL procedures
Examine table and object definitions
Develop and run batch scripts
Perform database administration
You can use SQL Command Line to generate reports interactively, to generate reports as batch processes, and to write the results to a text file, to a screen, or to an HTML file for browsing on the Internet.
Using SQL Command Line
This section describes SQL Command Line (SQL*Plus), a command-line utility to run SQL and PL/SQL.
This contains the following topics:
Before starting SQL Command Line, make sure that the necessary environmental variables have been set up properly. See Oracle Database Express Edition 2 Day DBA for information about setting environmental variables for SQL Command Line.
Starting and Exiting SQL Command Line
To start SQL Command Line from the operating-system command prompt, enter the following:
When prompted, enter the username and password of the user account (schema) that you want to access in the local database. For example, enter HR for the username and my_hr_password for the password when prompted.
You can also include the username and password when you start SQL Command Line. For example:
sqlplus hr/ my_hr_password
If you want to connect to a database running on a remote system, you need to include a connect string when starting SQL Command Line. For example:
sqlplus hr/ my_hr_password @ host_computer_name
After you have started SQL Command Line, the SQL prompt displays as follows:
At the SQL prompt, you can enter SQL statements.
When you want to exit SQL Command Line, enter EXIT at the SQL prompt, as follows:
Displaying Help With SQL Command Line
To display a list of Help topics for SQL Command Line, enter HELP INDEX at the SQL prompt as follows:
From the list of SQL Command Line Help topics, you can display Help about an individual topic by entering HELP with a topic name. For example, the following displays Help about the SQL Command Line COLUMN command, which enables you to format column output:
SQL HELP COLUMN
Entering and Executing SQL Statements and Commands
To enter and execute SQL statements or commands, enter the statement or command at the SQL prompt. At the end of a SQL statement, put a semi-colon (;) and then press the Enter key to execute the statement. For example:
SQL SELECT * FROM employees;
If the statement does not fit on one line, enter the first line and press the Enter key. Continue entering lines, and terminate the last line with a semi-colon (;). For example:
SQL SELECT employee_id, first_name, last_name
2 FROM employees
3 WHERE employee_id = 105 AND employee_id = 110;
The output from the previous SELECT statement is similar to:
EMPLOYEE_ID FIRST_NAME LAST_NAME
105 David Austin
106 Valli Pataballa
107 Diana Lorentz
108 Nancy Greenberg
109 Daniel Faviet
6 rows selected.
Note that a terminating semi-colon (;) is optional with SQL Command Line commands, such as DESCRIBE o r SET , but required with SQL statements.
SQL Command Line DESCRIBE Command
SQL Command Line provides the DESCRIBE command to display a description of a database object. For example, the following displays the structure of the employees table. This description is useful when constructing SQL statements that manipulate the employees table.
SQL DESCRIBE employees
EMPLOYEE_ID NOT NULL NUMBER(6)
LAST_NAME NOT NULL VARCHAR2(25)
EMAIL NOT NULL VARCHAR2(25)
HIRE_DATE NOT NULL DATE
JOB_ID NOT NULL VARCHAR2(10)
SQL Command Line SET Commands
The SQL Command Line SET commands can be used to specify various SQL Command Line settings, such as the format of the output from SQL SELECT statements. For example, the following SET commands specify the number of lines for each page and the number of characters for each line in the output:
SQL SET PAGESIZE 200
SQL SET LINESIZE 140
To enable output from PL/SQL blocks with DBMS_OUTPUT.PUT_LIN E, use the following:
SQL SET SERVEROUTPUT ON
To view all the settings, enter the following at the SQL prompt:
For information about the SQL Command Line SERVEROUTPUT setting to display output from a PL/SQL program, see “Inputting and Outputting Data with PL/SQL”.
SQL*Plus User’s Guide and Reference for information about setting up the SQL Command Line environment with a login file
Running Scripts From SQL Command Line
You can use a text editor to create SQL Command Line script files that contain SQL*Plus, SQL, and PL/SQL statements. For consistency, use the .sql extension for the script file name.
A SQL script file is executed with a START or @ command. For example, in a Windows environment, you can execute a SQL script as follows:
A SQL script file can be executed in a Linux environment as follows:
SQL START /home/cjones/my_scripts/my_sql_script.sql
You can use SET ECHO ON to cause a script to echo each statement that is executed. You can use SET TERMOUT OFF to prevent the script output from displaying on the screen.
When running a script, you need to include the full path name unless the script is located in the directory from which SQL Command Line was started, or the script is located in the default script location specified by the SQLPATH environment variable.
Oracle Database Express Edition 2 Day DBA for information about setting environment variables for Oracle Database Express Edition
SQL*Plus User’s Guide and Reference for information about setting the SQL Command Line SQLPATH environment variable to specify the default location of SQL scripts
Spooling From SQL Command Line
The SPOOL command can be used to direct the output from SQL Command Line to a disk file, which enables you to save the output for future review.
To start spooling the output to an operating system file, you enter the SPOOL command followed by a file name. For example:
SQL SPOOL my_log_file.log
If you want to append the output to an existing file:
SQL SPOOL my_log_file.log APPEND
To stop spooling and close a file, enter the following:
Using Variables With SQL Command Line
You can create queries that use variables to make SELECT statements more flexible. You can define the variable before running a SQL statement, or you specify that the statement prompts for a variable value at the time that the SQL statement is run.
When using a variable in a SQL statement, the variable name must be begin with an ampersand ( ).
This section contains the following topics:
For information about using bind variables in PL/SQL code, see “Using Bind Variables With PL/SQL”.
Prompting for a Variable Value in a Query
You can use to identify a variable that you want to define dynamically. In Example A-1, including the employee_id variable causes the SQL statement to prompt for a value when the statement is executed. You can then enter a value for the employee_id that corresponds to the employee information that you want to display, such as employee ID 125. Note that you can use any name for the variable, such as my_variable .
Example A-1 Prompting for a Variable Value in SQL Command Line
When you run the previous SELECT statement, the output is similar to:
Enter value for employee_id: 125
EMPLOYEE_ID LAST_NAME JOB_ID
125 Nayer ST_CLERK
Reusing a Variable Value in a Query
You can use to identify a variable that you want to define dynamically multiple times, but only want to prompt the user once. In Example A-2, including the column_name variable causes the SQL statement to prompt for a value when the statement is executed. The value that is entered is substituted for all remaining occurrences of column_name in the SQL statement.
Example A-2 Reusing a Variable Value in SQL Command Line
Defining a Variable Value for a Query
In Example A-3, the job_id variable is defined before running the SQL statement with the DEFINE command, and the defined value is substituted for the variable when the statement is executed. Because the variable has already been defined, you are not prompted to enter a value.
Example A-3 Defining a Variable for a Query in SQL Command Line