CpSc 3220 The 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

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 statement SELECT [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 be a column-name field a literal-value field a 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 database orders(orderID, customerID, OrderAmount) customer(customerID, FirstName, LastName)

The Customer Table from Ch 1 CustomerIDFirstNameLastName 1WilliamSmith 2NatalieLopez 3BrendaHarper

The Orders Table from Ch 1 OrderIdCustomerIDOrderAmount

SQL Select Examples We can write SQL statements for this database SELECT “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