1. Structured Query Language
56:150 Information System Design

2. Introduction
A unified language for defining, querying, modifying, and controlling the data in a relational database. (data manipulation, data definition, and data administration)
Officially pronounced as “ess-cue-ell”. But many people say “sequel”.

3. Select It lets you find and view your data in a variety of ways.
Basic Syntax
SELECT list_of_columns
FROM tables[s]
[WHERE search_conditions]

4. Examples SELECT * FROM products (* means all columns)
SELECT ProductName, Unitprice * UnitsOnOrder as [Ordered Amount] FROM products WHERE UnitsOnOrder > 0
SELECT ‘The highest price is ’, max(unitprice)
FROM Products

5. Use alias for tables SELECT prdct.productname], ctg.categoryname
FROM products as prdct, categories as ctg
WHERE ctg.CategoryID = prdct.categoryID;

6. Where Clause
Comparison operators (=, < , >, < >, and so on)
Combinations or logical negations of conditions (AND, OR, NOT)
Where unitprice < 5000 and unitprice > 2000
Ranges (Between, Not Between)
Where unitprice between 2000 and 5000
Lists (In, Not in)
Where state in (‘CA’, ‘IN’, ‘MD’)

7. Where Clause Unknown Values (Is Null, Is not Null)
Where productname is null
Character matches (Like and Not like)
Where phone not like ‘415%’
Wildcard % , any string of zero or more characters
Wildcard _ , any single character.

8. Other selection techniques
Order by {expression [ASC | DESC]}
Select productname, unitprice from products where unitprice between 20 and 50
order by price
Distinct
select distinct categoryID from products
Aggregate functions
sum, avg, count, max, min

9. Other selection techniques
Group by: divides the rows into sets
Having: puts a condition on the sets
Where eliminates rows before grouping, but having goes to work after grouping.
Example:
SELECT categoryID, avg(unitprice), count(productname) FROM products
group by categoryID
having count(productname) > 10

10. Query with subquery A subquery is a SELECT statement that nests
inside the WHERE, HAVING, or SELECT clause of another SELECT statement;
Inside an INSERT, UPDATE, or DELETE statement;
Inside another subquery

11. Example
SELECT CustomerID FROM orders WHERE orderid in (select orderid from [order details] where discount=0.15)
Alternative Way?
Select o.customerid from orders as o, [order details] as od
Where o.orderid = od.orderid and od.discount = 0.15

12. Update Syntax UPDATE table_name
SET column_name = expression
[WHERE search _ conditions]
Without where clause, update operation will affect all rows.

13. Delete Syntax DELETE FROM table_name
[WHERE search contiditions]
Without where clause, delete operation will influence all the rows.

14. Insert
Syntax
INSERT INTO tablename [(columnname, …)] VALUES (constant, …)

15. Create Create Tables Syntax Create Index Syntax
CREATE TABLE table_name
(column_name datatype [NULL | NOT NULL]
[, column_name datatype [NULL | NOT NULL] ]…)
Create Index Syntax
CREATE [UNIQUE] INDEX index_name
ON table_name (column_name)
Database, view can also be created by SQL

16. Other topics Transactions Stored-Procedures Triggers Outer Join Union
Data administration