CpSc 3220The Language of SQL

Chapters 1-4

SQL Background

• SQL was created at IBM as a language for SYSTEM-R, an early RDBM based on Codd’s work (Rockoff says RDBMs are called relational to indicate their tables are related. Not true.)

• Later used in other RDBMs • Standardized by ANSI and ISO in various

versions; SQL92, SQL99, … ,SQL2011• Commercial RDBMs rarely implement a fully-

standard version of SQL

Textbook Covers Three RDBMs

• SQL Server from Microsoft• Oracle from Oracle• MySQL from Oracle

We Will Concentrate on MySQL

• A link to an online MySQL reference manual http://dev.mysql.com/doc/refman/5.5/en/index.html

SQL is a Declarative Language

• Statements say WHAT we want, not HOW to get it

• Has some procedural elements• Three ‘sub-languages’: DML, DDL, DCL• We will spend most of our time on the DML part• There are several statement types in the DML

part of SQL • We will spend most of our time on the SELECT

statement

But First . . .

• Rockoff discusses SQL datatypes • There are a bunch – we concentrate on a few:– int– decimal– float– char– varchar– date– datetime– time

Back to the SELECT Statement

• We review the full SELECT syntax • We will only study part of it• We start with a very small part• First, we review the syntax notation used for

describing SQL statements

Syntax of the SELECT statementSELECT [ALL | DISTINCT | DISTINCTROW ] [HIGH_PRIORITY] [STRAIGHT_JOIN] [SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT] [SQL_CACHE | SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS] select_expr [, select_expr ...] [FROM table_references [WHERE where_condition] [GROUP BY {col_name | expr | position} [ASC | DESC], ... [WITH ROLLUP]] [HAVING where_condition] [ORDER BY {col_name | expr | position} [ASC | DESC], ...] [LIMIT {[offset,] row_count | row_count OFFSET offset}] [PROCEDURE procedure_name(argument_list)] [INTO OUTFILE 'file_name' [CHARACTER SET charset_name] export_options | INTO DUMPFILE 'file_name' | INTO var_name [, var_name]] [FOR UPDATE | LOCK IN SHARE MODE]]

Syntax Notation

• Information in upper case is ‘reserved’, must be spelled as given (but upper case isn’t required in actual SQL statements)

• Information in lower case must be further defined• The information inside [ ] is optional• The | symbol is used to indicate alternatives• The . . . symbol indicates (zero or more) repetitions • All other symbols are used as is

Some Syntax Notes

• SQL statements are generally case-insensitive• SQL is generally free-format• SQL identifier names are made up of letters,

numbers, special symbols, and spaces. (names with special symbols and spaces may require delimiters.) Fully defined in Reference Manual.

• Some DBMS (including MySQL) require statement terminators (;)

select_expr

• Made be either* a comma-separated list of fields

fields

• A field may bea column-name fielda literal-value fielda calculated or generated field made up of column-names, literal-values, operators, and/or functions

• Fields may have aliases

SQL allows Aliases DB elements

• Any select_expr can be given a new name:SELECT colexp AS aliasName FROM table;

The alias will be used in column headings• Tables can also be given aliases

SELECT colexp FROM table AS tableAlias;

Samples

• Suppose we have a database with two tables; orders and customers

• We use this notation to describe this databaseorders(orderID, customerID, OrderAmount)customer(customerID, FirstName, LastName)

The Customer Table from Ch 1CustomerID FirstName LastName

1 William Smith

2 Natalie Lopez

3 Brenda Harper

The Orders Table from Ch 1 OrderId CustomerID OrderAmount

1 1 50.00

2 1 60.00

3 2 33.50

4 3 20.00

SQL Select Examples

• We can write SQL statements for this databaseSELECT “Hello, World”;SELECT * FROM orders;SELECT firstName FROM customers;SELECT 2*OrderAmount FROM orders;SELECT “Amt doubled =”,2*OrderAmount FROM orders;SELECT concat(“Dr. ”, LastName) FROM customers;SELECT concat(“Dr. ”, LastName) AS Name FROM customers;

The DBs from the Rockoff book are available online

• Download the appropriate (MySQL) file from the site given in the CourseMaterials link on BB

• Use a text editor, open a blank file, cut and paste the script for a specific chapter to your open text file.

• Modify this file by adding the statements below at the beginning of the script

DROP DATABASE IF EXISTS yourDBname;CREATE DATABASE yourDBname;USE yourDBname;

• Save it with any name you choose with a suffix .sql• Use PHPMyAdmin to import and run the saved script