1. Single-Table Queries 1: Basics CS 320 Online

2. Review: SQL Command Types  Data Definition Language (DDL)  Used to create and modify database objects  Data Manipulation Language (DML)  Used to insert, update, delete, and view the data in database objects

3.  Query: question represented in a way a database can understand  SQL query components:  SELECT: columns whose values you want to retrieve  FROM: tables that contain the columns in the SELECT clause  WHERE: optional search condition to restrict which records are retrieved Database Queries

4. Programming Note: Before you can run SELECT queries, your database must contains data Run the scripts to insert the records in the CANDY database

5. CANDY database tables (with revised field names) CANDY_CUSTOMER CANDY_PURCHASE CANDY_CUST_TYPE CANDY_PRODUCT

6. Retrieving Data From a Single Table Basic syntax: SELECT field1, field2, … FROM tablename WHERE search_condition SELECT cust_id, cust_name FROM candy_customer WHERE cust_id = 1

7. Retrieving All Fields or All Records  To retrieve all fields in the table: use the "*" wildcard character  To retrieve all records in a table: omit the search condition SELECT * FROM tablename WHERE search_condition

8. Examples of Queries that Retrieve all Fields and all Records SELECT * FROM candy_purchase; SELECT * FROM candy_cust_type;

9. Search Conditions General format:  Operators: =,, =, <> or !=, BETWEEN, IN, LIKE Examples: FieldName Operator TargetValue prod_id = 1 purch_pounds > 5 prod_cost >= 9.99 purch_status != 'PAID' purch_pounds BETWEEN 5 AND 10 prod_id IN (1, 3, 5)

10. SearchTarget Values Numbers  Just type the number Text strings  Enclose in single or double quotes  Search for strings with embedded single quotes by typing \' or \" Dates  Enter as a text string in 'yyyy-mm-dd' format prod_id = 1 prod_cost >= 9.99 cust_name = 'Jones, Joe' prod_desc = 'Millionaire\'s Macadamia Mix' purch_date = '2004-10-28'

11. Using IN and BETWEEN IN: retrieves all matching values within a set of values BETWEEN: retrieves all matching values within a range of values (inclusive) WHERE cust_zip IN ('91211', '91212') WHERE prod_id BETWEEN 1 AND 3

12. Partial-text search: searches for part of a string within a character field  Use the % wildcard character to match 0 or more characters  Examples: Partial-Text Searches Using LIKE WHERE cust_zip LIKE '9121%' WHERE cust_name LIKE '%s' WHERE cust_name LIKE '%s%'

13. Searching for NULL Values NULL: undefined Search conditions for NULL and non- NULL values: WHERE fieldname IS NULL WHERE fieldname IS NOT NULL WHERE cust_phone IS NULL WHERE purch_delivery_date IS NOT NULL

14. Compound Search Conditions  Formed by connecting two or more search conditions using the AND or OR operator  AND: query only retrieves records for which both conditions are true  OR: query retrieves records for which either condition is true

15. Example Compound Search Conditions WHERE Condition1 AND Condition2 WHERE Condition1 OR Condition2 WHERE prod_id = 1 AND purch_date = '2008-10-28' WHERE prod_id = 1 OR prod_id = 3

16. Using AND and OR in Search Conditions Every expression must be well-formed:  Do this:  Not this: WHERE purch_date > '2004-10-28' AND purch_date < '2004-11-1' WHERE purch_date > '2004-10-28' AND < '2004-11-1'

17. MySQL evaluates AND expressions first, then OR expressions To force a specific evaluation order, place conditions to be evaluated first in parentheses! Order of AND/OR Evaluation SELECT cust_id FROM candy_customer WHERE cust_type = 'W' AND (cust_zip = '91209' OR cust_zip = '91212')

18. Test Yourself: How many fields and how many records will the following query retrieve? a. 7 fields and 14 records b. 14 fields and 7 records c. 7 fields and 9 records d. None of the above SELECT * FROM candy_purchase;

19. Test Yourself: How many fields and how many records will the following query retrieve? a. 7 fields and 14 records b. 14 fields and 7 records c. 7 fields and 9 records d. None of the above SELECT * FROM candy_purchase;

20. a. 4 b. 8 c. 9 d. 10 e. None of the above Test Yourself: How many CANDY_CUSTOMER records will the following query retrieve? SELECT cust_id FROM candy_customer WHERE cust_name LIKE '%s'

21. a. 4 b. 8 c. 9 d. 10 e. None of the above Test Yourself: How many CANDY_CUSTOMER records will the following query retrieve? SELECT cust_id FROM candy_customer WHERE cust_name LIKE '%s'

22. Test Yourself: How many records will the following query retrieve? a. 0 b. 8 c. 14 d. None of the above SELECT * FROM candy_purchase WHERE purch_status LIKE '%Paid%'

23. Test Yourself: How many records will the following query retrieve? a. 0 b. 8 c. 14 d. None of the above SELECT * FROM candy_purchase WHERE purch_status LIKE '%Paid%'

24. Test Yourself: How many records will the following query retrieve? a. 0 b. 3 c. 5 d. 8 e. None of the above SELECT * FROM candy_purchase WHERE purch_delivery_date = NULL AND purch_status = 'PAID'

25. Test Yourself: How many records will the following query retrieve? a. 0 b. 3 c. 5 d. 8 e. None of the above SELECT * FROM candy_purchase WHERE purch_delivery_date = NULL AND purch_status = 'PAID'