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Database Design Sections 13 & 16 - Introduction to HTML DB SQL editor, Introduction to SQL statements Using HTML_DB SQL editor Reference Lab #6 problem 1 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 Marge Hohly 2 Enter SQL command Marge Hohly 3 Display the Table structure Enter the following command: DESCRIBE MUSIC; The structure of the table should be shown. Results on next slide Marge Hohly 4 Music Table Structure Marge Hohly 5 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 Marge Hohly 6 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 omited 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; Marge Hohly 7 Resulting Screen Marge Hohly 8 Inserting Data INSERT INTO tablename (column1, column2,....) VALUES(value1,value2,...); Remember character data needs to be enclosed in single quotes. Marge Hohly 9 SQL DESCRIBE DESCRIBE <table name>; DESCRIBE employees; Try the last statement. Marge Hohly 10 Subset of data WHERE clause SELECT <column name 1, column name 2, etc.> FROM <table name> WHERE <condition>; SELECT first_name, last_name, salary FROM employees WHERE salary > 5000; Marge Hohly 11 Insert Data into table INSERT INTO <table name> VALUES (value 1, value 2, value 3, etc); INSERT INTO music VALUES (10,'Marge Hohly','Folk'); Marge Hohly 12 ALTER table structure ALTER TABLE <table name> ADD (<new_column_name> <data type>); Try to modify the structure of the MUSIC table Add a column (which you will misspell) COUNTRI instead of COUNTRY). Marge Hohly 13 Deleting a column from a table ALTER TABLE <table name> DROP COLUMN <column_name>; Now delete the column (COUNTRI) you just added. Marge Hohly 14 Deleting a row DELETE from <table name> WHERE <column_name> = 'some value' ; DELETE from music WHERE musicid = 10; DELETE from music WHERE type = ‘Folk’; Marge Hohly 15 Database Facts Currently 20% of the world's data resides in relational DBMSs. In the next two years, databases are expected to grow larger than 100 terabytes. A database this big would be able to store 100,000 copies of the Encyclopedia Britannica or 200,000 hours of music or about 10 billion web pages. The top 10 world's largest databases using the Oracle DBMS are: France Telecom, 29.2TB -- a communications company (a TB is a terabyte equivalent to 1,000 gigabytes) Amazon.com with, 13 TB -- selling books and merchandise The Claria Corporation,12TB -- Internet behavioral marketing company tracking Internet user behavior Marge Hohly 16 HTML DB 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 HTML DB editor These tables are available on the Student Resource web page for this class Marge Hohly 17 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. Marge Hohly 18 Categories of SQL Statements Data manipulation language (DML) statements 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. Begin with INSERT, UPDATE, DELETE, or MERGE Used to modify the table by entering new rows, changing existing rows, or removing existing rows. 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. Marge Hohly 19 16.2.6 Questions 1. The Fast Foods database consists of how many tables? ____ tables 2. How is the F_SHIFTS table related to the F_STAFFS table? 3. What are the names of the columns in the F_CUSTOMERS table? 4. How many rows of data have been entered in the F_PROMOTIONAL_MENUS table? 5. In the F_FOOD_ITEMS table, column _________ is a foreign-key column. What table and column is this key referencing? 6. List the primary key to foreign key relationships required to go from the F_SHIFTS table to the F_REGULAR_MENUS table. 7. Which table(s) contain null values? Marge Hohly 20 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. Marge Hohly 21 Selection vs. Projection SELECT salary FROM employees WHERE 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 Marge Hohly 22 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 isa 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. Marge Hohly 23 Arithmetic Expressions Create expressions with number and date data by using arithmetic Operator operators. + Description Add - Subtract * Multiply / Divide Marge Hohly 24 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 Marge Hohly 25 Rewrite in order of precedence You want to calculate the annual salary if the employee received $100 raise each month Revise the following statement in the correct order of precedence to get the desired results Run each example in the editor SELECT last_name, salary, 12*salary+100 FROM employees; Marge Hohly 26 Null Values in Arithmetic Expressions SELECT last_name, salary, commission_pct, salary*commission_pct FROM employees; SALARY COMMISSION_PCT SALARY*COMMISSION_PCT 2500 (null) (null) 10500 .2 2100 11000 .3 3300 8600 .2 1720 7000 .15 1050 (null) (null) (null) Marge Hohly 27 Practice SELECT * FROM d_songs; SELECT id, title, duration, artist, type_code FROM d_songs; SELECT id, title, artist, FROM d_songs; SELECT last_name, salary, salary – 300 FROM employees; SELECT last_name, salary, salary * 1.05 FROM employees; Marge Hohly 28 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 Marge Hohly 29 Using Aliases SELECT last_name name, salary AS Salary, salary*12 “Annual Salary” FROM employees; NAME SALARY Annual Salary Whalen 4400 52800 Hartstein 13000 156000 Fay 6000 72000 Marge Hohly 30