SQL Select Statement

IST359

Agenda

• SQL SELECT = Most Important Statement• Understanding Fudgemart• Select from, where, order by• Top and distinct keywords• Table joins• Column and table aliasing

SQL SELECT Reads Data

SELECT col1, col2, ...FROM tableWHERE conditionORDER BY columns

Columns To Display

Table to use

Only return rows

matching this

conditionSort row

output by data in these

columns

SELECT Demo

• Basic SELECT–Columns–Where ( AND .vs OR)–Order by–TOP / Distinct

SELECT

HOW WE SAY IT1. SELECT (Projection)2. TOP/ DISTINCT3. FROM4. WHERE5. ORDER BY

HOW IT IS PROCESSED1. FROM2. WHERE3. SELECT (Projection)4. ORDER BY5. TOP / DISTINCT

Fudgemart – Conceptual

Fudgemart - Internal

JOINS

• JOINS let you combine data from more than one table into your query output

• Most of the time you join on PK-FK pairsSELECT *

FROM tableaJOIN tableb ON acol =

bcol

Demo – Table Joins

• Select JOINS– Inner / Equijoin• Basic join type

–Table and Column Aliasing• Makes it easier to know what comes from where

–Outer joins (Left / Right)• Include non-matching records across joins

–Multi-table joins

Work in Groups. Try these.

1. All Employees working in the ‘Hardware’ department making less than $15/hr

2. Names and retail prices of the top 5 products3. Product name, product wholesale price , and

vendor name for products supplied by vendor ‘Mikee’

4. List of employee names and their supervisor’s names.