1. SQL
Key Revision Points

2. SQL SQL (Structured Query language) pronounced “sequel”
Declarative language consisting of commands called SQL statements
Statements usually written in CAPS
Statements contain clauses – individual commands
Can create, update, query databases using SQL

3. SELECT (SELECT…FROM…WHERE)
The SELECT clause is used to query (search) the database
It SELECTS the records matching the criteria you specify

4. SELECT - Basic SELECT * FROM dogs SELECT dogName FROM dogs
Returns all the data from all the records in the table called dogs (uses a wildcard)
SELECT dogName FROM dogs
Returns just the name for all the records in the table called dogs
SELECT dogName, dogBreed, Age FROM dogs
Returns the name, breed and age for all the records in the table called dogs

5. SELECT - Advanced
Records can be filtered using arithmetic and Boolean operators
SELECT dogName, Age FROM dogs WHERE Age <=5
SELECT dogName FROM dogs WHERE dogBreed=“Jack Russell”
SELECT dogName, dogColour FROM dogs WHERE Age<5 OR dogBreed=“Chihuahua”
SELECT dogName, dogColour FROM dogs WHERE dogName=“Killer” AND dogBreed=“Chihuahua”
Syntax in the WHERE clause the same as used in Python if/while statements i.e. standard arithmetic and Boolean operators

6. SELECT Syntax
Note from previous examples that syntax is always the same:
SELECT dogName, dogColour FROM dogs WHERE Age<5 OR dogBreed=“Chihuahua”
What to fields to display in the results
Table containing the data
Criteria or conditions

7. INSERT (INSERT INTO…VALUES)
INSERT clause used to ADD records to an existing database

8. INSERT - Basic INSERT INTO dogs VALUES (“Psycho”, “Poodle”, “Grey”, 5)
Inserts the record into the dogs table

9. INSERT – Advanced/Syntax
If you want to add a partial record i.e. not all the fields you must also specify the field names after the table name
INSERT INTO dogs(dogName, age) VALUES (“Mr Fluffy”,4)
Which table/fields to insert data into
What data to insert into these fields*
* Must have the same number of fields/values and must be in the same order

10. UPDATE (UPDATE…SET…WHERE)
UPDATE clause used to change existing records in a database table.

11. UPDATE - Basic
UPDATE dogs SET dogName=“Mr. Fuzzychops” WHERE dogName=“Bert”
Changes Bert’s name to Mr. Fuzzychops
UPDATE dogs SET dogName=“Jason Bieber” WHERE dogID=5
Dog #5’s name is set to Jason Bieber
UPDATE dogs SET dogBreed=“Old Dog” WHERE age>10 AND dogBreed=“Alsatiopoodle”
Boolean in where clause may change multiple records i.e. all alsatiopoodles over 10 years old

12. UPDATE - Syntax Syntax always the same
UPDATE dogs SET dogBreed=“Old Dog” WHERE age>10 AND dogBreed=“Alsatiopoodle”
Table containing existing data
Field to change and new data
Criteria used to select the records to be changes

13. Sorting
You can sort the results of a SELECT query using an ORDER BY clause
SELECT dogName, dogColour
FROM dogs
WHERE Age<5 OR dogBreed=“Chihuahua”
ORDER BY dogName ASC
Use ASC to sort A-Z, 0-9 etc.
Use DESC to sort Z-A, 9-0 etc.

14. Indexing (Create Index…On)
To add a named index
CREATE INDEX dogIndex ON dogs(dogName)

15. Textbook
Textbook pages 52, 53, 56