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Guide to Oracle SQL (University at Buffalo Version)

Maintaining a Database using SQL Statements

Oracle uses the Structured Query Language (SQL) to create and maintain the database and tables. SQL [rovides statements that allow database administrators and users to perform create, read, update, and delete (CRUD) operations on a database. SQL is broken down into four (4) areas: a data query language (DQL), a data definition language (DDL), a data control language (DCL), and a data manipulation language (DML). SQL statements are not case-sensitive. I almost always try to upper case my SQL statements just for readability. I also try to use camel-case fo my database, table, and field names. For example, employeeTable and firstName.

To use Oracle on your local machine, you need to download Oracle Database Express 18c page. After you install 18c, then you can download and install SQL Developer.

If you are using SQL Developer, then right-click on your connection in the SQL developer Connections window. To create a new connection, click the "plus-sign" icon in the "Oracle Connections" pane. Then, you may have to change the connect type from "Basic" to "TNS".

Then choose Open SQL Worksheet. This is where you can enter SQL statements.

The CREATE Statement

The SQL CREATE statement can be used to create a new database or a new table within an existing database if you have permissions that allow you to create a new database.


The SQL CREATE DATABASE databaseName statement can be used to create a new database.

  Database JIMTEST created.
Figure 2-1: The CREATE DATABASE Statement

The CREATE TABLE Statement

The SQL CREATE TABLE tableName statement can be used to create a new table within an existing database.

  jimID NUMBER(9),
  firstName VARCHAR2(25) NOT NULL,
  lastName VARCHAR2(25) NOT NULL,
  Table JIMTABLE created.
Figure 2-2: The CREATE TABLE Statement

The DROP TABLE Statement

The SQL DROP TABLE tableName statement can be used to delete a within an existing database.

  Table "JIMTABLE" dropped.
Figure 2-3: The DROP TABLE Statement

The DESCRIBE Statement

In SQL Developer pressing the SHIFT-F4 key displays the table structure.

DESCRIBE jimTable;
1 JIMID       NUMBER(9,0)          No                      1 
2 FIRSTNAME   VARCHAR2(25 BYTE)    No                      2 
3 LASTNAME    VARCHAR2(25 BYTE)    No                      3
Figure 2-4: The DESCRIBE Statement Using the Run Button in SQL DEVELOPER

The INSERT Statement

The INSERT statement is used to add a record to a table. String (VARCHAR2) values should be enclosed in single quotes (''). In SQL Developer, if you are entering multiple statements you need to highlight all the statements before clicking the run icon (run icon).

(jimID, firstName, lastName)
(1, 'Jim', 'Gerland');
(jimID, firstName, lastName)
(2, 'Phil', 'Phailure');
(jimID, firstName, lastName)
(3, 'Sally', 'Smart');
1 row inserted.
1 row inserted.
1 row inserted.
Figure 2-5: The INSERT Statement

In SQL Developer, click the Commit (Commit icon) icon to apply the results of your INSERT query to your database.

The SELECT Statement

The SELECT statement is used to retreive information from the database.

Using the SELECT Statement To Retreive Records

The asterisk (*) is used as a wildcard. It is used to retreive all the fields in the table.

FROM jimTable;
1 1     Jim       Gerland
2 2     Phil      Phailure
3 3     Sally     Smart
Figure 2-6: The SELECT All Fields Statement

If you click the run script icon (run script icon) in SQL developer you get a different type of output.

FROM jimTable;
Figure 2-6a: The SELECT All Fields Statement

Using the SELECT Statement To Retrieve Certain Fields

You can also name the fields you would like return using the SELECT field[s] statement.

SELECT firstName, lastName 
FROM jimTable

1 Jim       Gerland
2 Phil      Phailure
3 Sally     Smart
Figure 2-7: The SELECT Certain Fields Statement

The UPDATE Statement

The UPDATE statement can be used to modify an existing record in a table.

UPDATE jimtable 
SET firstName = 'James' 
WHERE jimID = 1;

1 row updated.
Figure 2-8: The UPDATE Statement

The DELETE Statement

The DELETE statement can be used to remove an existing record from a table.

DELETE FROM jimtable 
WHERE jimID = 1;

1 row deleted.
Figure 2-9: The DELETE Statement

The TRUNCATE Statement

The TRUNCATE statement is used to remove all the records in a table but keep the strucure (fields) of the table intact.

Figure 2-10: The UPDATE Statement

SQL Comments

It is important to comment your SQL code. This helps you when you need to go back and modify your code and it helps other devlopers who will need to maintain you code after you move on to new, more challenging projects. SQL provides two (2) types of comments. single line comments (--) and multiple line comments (/* */).

-- This is a single line comment
  This is a 
  multiple line 
SELECT * FROM countries;

   COUNTRY COUNTRY_NAME                    REGION_ID
---------- ------------------------------ ----------
         1 Argentina                               2
         2 Brazil                                  2
         3 Canada                                  2
         4 United States                           2
         5 Mexico                                  2
Figure 2-11: SQL Comments

Task - Create, Populate, and Display an employees Table


  1. Open SQL Developer
  2. Connect to your database instance
  3. Open a new SQL editor window
  4. Enter code to CREATE an "employees" table with these fields:
    employee_id NUMBER NOT NULL, first_name VARCHAR2(20),
    last_name VARCHAR2(25), email VARCHAR2(25), phone_number VARCHAR2(20),
    hire_date DATE, job_id VARCHAR2(10), salary NUMBER(8,2), commission_pct NUMBER(8,2), and
    department_id NUMBER(3) with employee_id as the PRIMARY KEY
  5.  INSERT these records into the "employees" table:
    • 176, Sarah, Hall,, 7165551231, to_date('10-SEP-2009', 'DD-MON-YYYY'), 125000, SA_MAN, 80
    • 102, Allison, Felix,, 7165551232, to_date('10-OCT-2008', 'DD-MON-YYYY'), 45000, IT_PROG, 60
    • 201, LoLo, Jones,, 7165551234, to_date('10-SEP-2012','DD-MON-YYYY'), 55000, MK_REP, 20
    • 200, Steve, Scott,, 7165551235, to_date('10-MAR-2011','DD-MON-YYYY'), 55000, AD_ASST, 90
    • 202, Charlie, Wertz,, 7165551236, to_date('01-SEP-1989','DD-MON-YYYY'), 555000, SA_MAN, 80
  6. Display the employees table date (use SELECT).
  7. Save your SQL query script as "create_employees.sql".

When you have this Assignment ready for me to view and grade, you should click on this assignment and then choose "Add a File" and upload your create_employees.sql file, so I can download it and grade your work.

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