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Marge Hohly 2
Using APEX SQL editor You may either type the command into the
SQL editor or use the cut and paste option If you are going to cut/paste the command
copy the command from the word document into NotePad. This will drop out hidden characters.
Next copy the command from the NotePad into the editor
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Display the Table structure
Enter the following command: DESCRIBE MUSIC;
The structure of the table should be shown.
Select command structure SELECT field1, field2, field3
FROM table_nameWHERE condition;
Try the following commandSELECT employee_id, first_name, last_name, department_idFROM employees;
SELECT employee_id, first_name, last_name, department_idFROM employeesWHERE department_id = 90;
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Insert Data Note the data types for each column Inserting data into the table. Since the table is empty all fields need to be
populated, so column names can be omitted INSERT INTO music
VALUES (10,'Marge Hohly','Folk'); This will insert one record into the table Next display the contents of the table to view the
data SELECT *
FROM music;
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Typical error messages The following statement has a spelling error: SELCT *
FROM employees;
The error message is: ORA-00900: invalid SQL statement
The following statement incorrectly names the table employee instead of employees:
SELECT *FROM employee;
The error message is: ORA-00942: table or view does not exist
Run the correct statement.
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Subset of data WHERE clause
SELECT <column name 1, column name 2, etc.> FROM <table name>WHERE <condition>;
SELECT first_name, last_name, salaryFROM employeesWHERE salary > 5000;
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Application Express SQL editor The SQL course will use the three following sets of database tables for
examples and practice exercises.
Oracle tables: COUNTRIES, REGIONS, DEPARTMENTS, EMPLOYEES, JOBS, JOB_HISTORY AND JOB_GRADES
DJs on Demand database tables: D_CDS, D_PACKAGES, D_TYPES, D_THEMES, D_CLIENTS, D_VENUES, D_SONGS, D_TRACK_LISTINGS, D_PARTNERS, D_EVENTS, D_PLAY_LIST_ITEMS, D_JOB_ASSIGNMENTS
Global Fast Foods database tables: F_CUSTOMERS, F_REGULAR_MENUS, F_PROMOTIONAL_MENUS, F_SHIFTS, F_STAFFS, F_FOOD_ITEMS, F_ORDERS, F_ORDER_LINES, F_SHIFT_ASSIGNMENTS
Print out these tables for your reference when using the Application Express editor
These tables are available on the Student Resource web page for this class
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Review the tables There are six properties of tables in a relational
database: Property 1: Entries in columns are single-valued. Property 2: Entries in columns are of the same kind. Property 3: Each row is unique. Property 4: Sequence of columns is insignificant. Property 5: Sequence of rows is insignificant. Property 6: Each column has a unique name.
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Categories of SQL Statements Data manipulation language (DML) statements
Begin with INSERT, UPDATE, DELETE, or MERGE Used to modify the table by entering new rows, changing existing rows, or
removing existing rows.
Data definition language (DDL) statements set up, change, and remove data structures from the database. The keywords CREATE, ALTER, DROP, RENAME, and TRUNCATE begin DDL
statements.
Transaction control (TCL) statements are used to manage the changes made by DML statements. Changes to the data are executed using COMMIT, ROLLBACK, and
SAVEPOINT. TCL changes can be grouped together into logical transactions.
Data control language (DCL) keywords GRANT and REVOKE are used to give or remove access rights to
the database and the structures within it.
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KEYWORD, CLAUSE, STATEMENT Throughout this course, the words keyword,
clause, and statement are used as follows: A keyword refers to an individual SQL element.
For example, SELECT and FROM are keywords. A clause is a part of a SQL statement.
SELECT employee_id, last_name, .... is a clause.
A statement is a combination of two or more clauses.SELECT *FROM employees;
is a SQL statement.
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Selection vs. Projection SELECT salary
FROM employeesWHERE last_name like ‘Smith’;
Selection (row) Projection (column)
ID First_name Last_name salary
10 John Doe 4000
20 Jane Jones 3000
30 Sylvia Smith 5000
40 Hai Nguyen 6000
SELECT statement
SELECT statements can provide the same information depending on how they are written
Example: SELECT *
FROM d_songs; SELECT id, title, duration, artist,
type_codeFROM d_songs;
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SELECTION SELECT *
FROM employeesWHERE department_id = 60;
SELECT * FROM employeesWHERE salary > 10000;
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Projections
A subset of columns SELECT first_name, last_name, salary
FROM employees; SELECT id, title, artist
FROM d_songs;
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Arithmetic Expressions Create expressions
with number and date data by using arithmetic operators. Operator Description
+ Add
- Subtract
* Multiply
/ Divide
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Operator Precedence Operator Precedence
Multiplication and division take priority over addition and subtraction.
Operators of the same priority are evaluated from left to right.
Parentheses are used to force prioritized evaluation and to clarify statements.
Remember: Please excuse my dear aunt Sally
() ^ * / + -
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What is null? If a row lacks the data value for a particular
column, that value is said to be null, or to contain a null. A null is a value that is unavailable, unassigned, unknown, or inapplicable.
A null is not the same as zero. Zero is a number.
A null is not a space. Space is a character.
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Column Alias Renames a column heading Is useful in naming columns of
derived values Immediately follow the column name Uses optional AS keyword between
the column name and alias Required double quotation marks if it
contains spaces or special characters or is case sensitive