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DBS201: Introduction to Structure Query Language (SQL)

Lecture 1

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Agenda

The basic commands and functions of SQL How to use SQL to query a database to extract

useful information

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Introduction to SQL

SQL: Structured Query Language Designed specifically for communicating with

databases SQL functions fit into two broad categories:

Data definition language Data manipulation language

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Introduction to SQL (continued)

Data definition language SQL includes commands to create

Database objects such as tables, indexes, and views Commands to define access rights to those database

objects

Data manipulation language Includes commands to insert, update, delete, and

retrieve data within the database tables

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Introduction to SQL (continued)

SQL is relatively easy to learn

Basic command set has a vocabulary of less than 100 words

Sample vocabulary: CREATE COLLECTION CREATE TABLE CREATE VIEW

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Introduction to SQL (continued)

Sample vocabulary (continued): DROP COLLECTION DROP TABLE DROP VIEW ALTER INSERT SELECT DELETE

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Introduction to SQL (continued)

American National Standards Institute (ANSI) prescribes a standard SQL

Several SQL dialects exist

Oracle, MySQL, Access etc

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Data Manipulation Commands

* Ignore Insert command for now

*

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Sample Table: PART

PARTNUMBER

PARTDESC

ONHAND CLASS WAREHOUSE PRICE

AX12 Iron 104 HW 3 23.95

AZ52 Dartboard 20 SG 2 12.95

BA74 Basketball 40 SG 1 29.95

BH22 Cornpopper 95 HW 3 24.95

BT04 GasGrill 11 AP 2 149.99

BZ66 Washwer 52 AP 3 399.99

CA14 Gridle 78 HW 3 39.99

CB03 Bike 44 SG 1 299.99

CX11 Blender 112 HW 3 22.95

CZ81 Treadmill 68 SG 2 349.99

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Listing Table Rows

SELECT Used to list contents of table

Syntax SELECT Field1, Field 2,…

FROM tablename

WHERE Condition 1 AND/OR Condition 2

ORDER BY Field1, Field 2,…

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Listing Table Rows

At a minimum, must specify what you want to select and where you want to select it from

SELECT PART_NUMBER FROM PART

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Listing Table Rows, specifying a specific field name

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Listing All Table Rows

Asterisk can be used as wildcard character to list all attributes

SELECT * FROM PART

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Listing Table Rows with * to represent all field names

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Selecting Rows with Comparison Operators

Select partial table contents by placing restrictions on rows to be included in output Add conditional restrictions to the SELECT

statement, using WHERE clause

SELECT * FROM PART WHERE ON_HAND > 30

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Listing Table Rows with * to represent all field names

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Comparison Operators

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Selecting Rows with Comparison Operators

SELECT * FROM PART WHERE PART_NUMBER = ‘AX12’

Note criteria is inParenthesis – PART_NUMBER is a character field

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Sorting Output

Data is displayed in the order which it was added to the tables initially

To change the order the data is displayed in, use the ORDER BY clause in the SELECT statement

SELECT * FROM PART ORDER BY ON_HAND

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Sorting Output – Single Column

SELECT * FROM PART ORDER BY ON_HAND

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Sorting Output – Multiple Columns

SELECT * FROM PART ORDER BY PRICE, PART_NUMBER

Note how boat name is sorted within owner num

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Sorting Output

Data is displayed in the order which it was added to the tables initially

To sort data in descending order, use the DESC keyword after each field specified in the ORDER BY clause that is to be displayed in descending order

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In Summary

SELECT statement Used to list contents of table

Syntax SELECT Field1, Field 2,…

FROM tablename

WHERE Condition 1 AND/OR Condition 2

ORDER BY Field1, Field 2,…

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Comparison Operators