Download Ch 3

Unit 3
SQL
英文版：Chap 3 “SQL”
中文版：第4章 “結構化查詢語言”
Database System Concepts, 5th Ed.
©Silberschatz, Korth and Sudarshan
See www.db-book.com for conditions on re-use
Chapter 3: SQL
 Data Definition
 Basic Query Structure
 Set Operations (union, intersect, except/differentiate)
 Aggregate Functions (count, sum, average, min, max – group by)
 Null Values (is [not] null)
 Nested Subqueries (in, exist, empty)
 Complex Queries (as, with)
 Views (create view X as/ select … into cursor)
 Modification of the Database (delete, insert, update)
 Joined Relations**
Database System Concepts, 5th Edition, Oct 5, 2006
3.2
©Silberschatz, Korth and Sudarshan
History
 IBM Sequel language developed as part of System R project at the
IBM San Jose Research Laboratory
 Renamed Structured Query Language (SQL)
 ANSI and ISO standard SQL:

SQL-86

SQL-89

SQL-92

SQL:1999 (language name became Y2K compliant!)

SQL:2003
 Commercial systems offer most, if not all, SQL-92 features, plus
varying feature sets from later standards and special proprietary
features.

Not all examples here may work on your particular system.
Database System Concepts, 5th Edition, Oct 5, 2006
3.3
©Silberschatz, Korth and Sudarshan
Domain Types in SQL
 char(n). Fixed length character string, with user-specified length n.
 varchar(n). Variable length character strings, with user-specified maximum






length n.
int. Integer (a finite subset of the integers that is machine-dependent).
smallint. Small integer (a machine-dependent subset of the integer
domain type).
numeric(p,d). Fixed point number, with user-specified precision of p digits,
with n digits to the right of decimal point.
real, double precision. Floating point and double-precision floating point
numbers, with machine-dependent precision.
float(n). Floating point number, with user-specified precision of at least n
digits.
More are covered in Chapter 4.
Database System Concepts, 5th Edition, Oct 5, 2006
3.4
©Silberschatz, Korth and Sudarshan
Application-Dep. Data Type (VFP)















Visual FoxPro
SQL Server
Abbreviation
Data Type
Data Type
----------------------------------------C
Character
char
Y
Currency
money
D
Date
datetime
T
DateTime
datetime
B
Double
float
F
Float
float
G
General
image
I
Integer
int
L
Logical
bit
M
Memo
text
N
Numeric
float
P
Picture
image
Database System Concepts, 5th Edition, Oct 5, 2006
3.5
©Silberschatz, Korth and Sudarshan
SQL for Relational Database
 Data Definition Language (DDL)

Create table S …

Create view V …

Alter table S…

Drop table S
 Data Manipulation Language (DML)

Insert into S …

Delete from S …

Update S set …
 Query Language

Select – from – where
Database System Concepts, 5th Edition, Oct 5, 2006
3.6
©Silberschatz, Korth and Sudarshan
DDL & DML (#1) create, insert

create database mydata; // mkdir d:\test (Visual Foxpro Command)

use mydata; //cd d:\test (Visual Foxpro Command)
 create table S (SN char(5), sname char(20), status int, city char(15));
// create table S (SN char(5), sname char(20), status int, city
char(15), primary key (`SN`), check status>0 );
 insert into S values('S1','Smith', 10, 'London');
 insert into S values('S2','Jones', 20, 'Paris');
 insert into S values('S3','Blake', 30, 'Paris');
藍色：Foxpro 指令
綠色：其他相關指令
MySQL - ; 表示提交
 insert into S values
('S4','Clark', 40, 'London'),('S5','Adams', 50, 'Tokyo');
Database System Concepts, 5th Edition, Oct 5, 2006
3.7
©Silberschatz, Korth and Sudarshan
DDL & DML (#2) update/delete, alter/drop
 update S set city='Taipei' where SN='S5‘;
 update S set city='Taipei' where city='Tokyo‘;
 delete from S where SN='S1‘;
 delete from S where where city='Tokyo‘;
 alter table S add rec char(10);
 alter table S modify rec integer;
 alter table S drop rec;
 drop table S;
Database System Concepts, 5th Edition, Oct 5, 2006
3.8
©Silberschatz, Korth and Sudarshan
DDL & DML (#3) create view/ drop
 create view temp as
(select SN, sname, city from S where SN <> 'S4') ;
 drop view temp;

Visual Foxpro Commands:

// select SN, sname, city from S where SN <> 'S4' into cursor temp

// select SN, sname, city from S where SN <> 'S4' into table temp

// drop table temp

// select SN, sname, city from S where SN <> 'S4' into array temp
Database System Concepts, 5th Edition, Oct 5, 2006
3.9
©Silberschatz, Korth and Sudarshan
DDL & DML (#4) e.g. table P
 create table P (PN char(5), pname char(20), weight int, color char(10));
//create table P (PN char(5), pname char(20), weight int, color char(10),
primary key (`PN`));
 insert into P values('P1','PnameA', 151, ‘red');
 insert into P values('P2','PnameB', 122, ‘red');
 insert into P values('P3','PnameC', 143, ‘green');
 insert into P values('P4','PnameD', 114, ‘white');
Database System Concepts, 5th Edition, Oct 5, 2006
3.10
©Silberschatz, Korth and Sudarshan
DDL & DML (#5) e.g. table SP
 create table SP (SN char(5), PN char(5), price float(5,2), qty int);
// create table SP (SN char(5), PN char(5), price float(5,2), qty int,
primary key (`SN`,`PN`),
foreign key (SN) references S(SN) on delete restrict on update cascade,
foreign key (`PN`) references P(PN) on delete restrict on update cascade);
 insert into SP values('S4','P2', 9.99, 420);
 insert into SP values('S4','P3', 6.66, 430);
 insert into SP values('S2','P2', 9.88, 220);
 insert into SP values('S2','P4', 7.77, 240);
 insert into SP values('S3','P3', 6.55, 330);
Database System Concepts, 5th Edition, Oct 5, 2006
3.11
©Silberschatz, Korth and Sudarshan
Query Language (#1, set operators)


------"Project" and "Restrict" ----------
select * from S;

select SN, sname, city from S where SN <> 'S4' ;

select * from S where city like '%on%' or sname like 'B____‘;

select * from S where city is null and sname is not null;
------"Union"----------
select * from S union select * from S;

select * from S where status >= 30
union select * from S where status <=10;


select * from S where status >= 30 or status <=10;
------ for "intersection" and "difference"----------
select * from S where SN in (Select SN from SP);

select * from S where SN not in (Select SN from SP); // 一般用法(無實際供貨)

// select * from SA where SN in (select SN from SB); //用於交集(子公司A,B共同供貨商)

MySQL Ver 5. 不支援 Intersect, except 這兩個指令
Database System Concepts, 5th Edition, Oct 5, 2006
3.12
// 一般用法(有實際供貨)
©Silberschatz, Korth and Sudarshan
Query Language (#2, set operators)

------"Cartesian Product" and "Join" ----------
select * from S, P;

select SN, PN from S, P;

// ex: 紫微斗數資料窮舉，

// (命宮，星宿) 是類似 S x P 的全部列表

select * from S, SP;

select S.SN, sname, city, PN, price, qty
from S, SP where S.SN=SP.SN;


// select SN, PN from S, SP; <--- why not? 因 SN名稱重複
select S.SN, P.PN, Price, qty, weight from S, P, SP
where S.SN=SP.SN and SP.PN=P.PN;

// 來自三個表格合組的大表格 S
Database System Concepts, 5th Edition, Oct 5, 2006
3.13
P
SP
©Silberschatz, Korth and Sudarshan
Query Language (#3, qualifiers)

------ qualifier: “union all”, “select distinct” ----------
select * from S union all select * from S; //例如摸彩卷
// (Error) create view test as (select * from S union all select * from S);


select PN from SP; // P# 重複出現 因為不止一家賣

select distinct PN from SP;

select PN, city from S, SP where S.SN=SP.SN; // 調查P#可什麼地方有賣

select distinct PN, city from S, SP where S.SN=SP.SN;
------ qualifier: order by [asc/desc], limit ----------
select * from SP order by PN;

select * from S,SP
where S.SN=SP.SN and city= 'Taipei' order by Price limit 5;

select S.SN, sname, city, PN, price, qty from S, SP
where S.SN=SP.SN order by PN asc, price desc; // P#遞增
P#同則 price 遞減
Database System Concepts, 5th Edition, Oct 5, 2006
3.14
©Silberschatz, Korth and Sudarshan
Query Language (#4, adv. commands)

------ advanced examples: as ----------
select SN, PN, price, qty as boxes, price*qty as total from SP; // 欄位變名

select S.SN, sname, city, PN, price, qty, price*qty as total
from S, SP where S.SN=SP.SN; // 即使進行 Join 亦可使用欄位變名

select First.SN, Second.SN from S as First, S as Second
where First.city=Second.city and First.SN < Second.SN; // 表格變名

------ advanced examples: having ----------
select S.SN, sname, city, PN, price, qty, price*qty as total
from S, SP where S.SN=SP.SN having total > 2000;
// having 是全部指令執行之後，用新完成的表單做後處理
//
上面指令在執行 having 條件之前變名已完成, 才可以引用 total 欄位
// 以下兩個指令結果相同，過程可能不相同
// select * from S where status >=20;
// select * from S having status >=20;
Database System Concepts, 5th Edition, Oct 5, 2006
3.15
©Silberschatz, Korth and Sudarshan
Query Language (#5, aggregation)

Aggregation Function (avg/min/max/sum/count, group by)
 select * from SP where PN='P3';
 select count(*) from SP where PN='P3';
Aggregation +group by 和
having 一樣是後處理指令
 select max(price) from SP;
 select max(price) from SP where PN='P3';
 select PN, max(price) from SP group by PN;
 select SN,PN, price, qty, (price*qty) as total from SP;
 select SN, sum(price*qty) as fortune from SP group by SN;
 select SN, sum(price*qty) as fortune from SP group by SN
having fortune >5000 order by fortune desc;
 注意，group by 不保證「非其所指定的屬性」之值(例如PN之外的SN)，
該值將會是 group 起來的所有tuples中的任何值。
 select PN, max(price), min(price) from SP group by PN; (保證PN)
此例SN,
 select SN, PN, max(price) from SP group by PN; (不保證SN之值)
#6, #7
 select * from SP where PN='P2'; (比較上例，查看SN之值)
示範各種
*如果 A B 查 group by A/B’s primary key, 則 A/B 各欄之值亦可保證。
解決之道
 select PN, color, max(price) from SP, P where SP.PN=P.PN group by PN;
Database System Concepts, 5th Edition, Oct 5, 2006
3.16
©Silberschatz, Korth and Sudarshan
Query Language (#6, subquery)

Subquery (in, exists, some/all)
 select SN, PN, price as max_price_of_PN from SP
where (PN, price) in (select PN, max(price) from SP group by PN);
 select SN, PN, price as max_price_of_PN from SP
where (PN, price) = some (select PN, max(price) from SP group by PN);
 select SN, PN, price as max_price_of_PN from SP
where price >= all (select price from SP as SP2 where SP.PN=SP2.PN);
 select SN, PN, price as max_price_of_PN from SP
where price= (select max(price) from SP as SP2 where SP.PN=SP2.PN);
select * from S where SN in (select SN from SP); // 有實際供貨的廠商
 select * from S where exists (select * from SP where SP.SN=S.SN);

// select * from S where status > all(select // 比全部有賣P6的廠商評價都高
//
status from S,SP where S.SN=SP.SN and PN='P6');
// select * from S where status <= some(select
//
status from S,SP where S.SN=SP.SN and PN='P6');
Database System Concepts, 5th Edition, Oct 5, 2006
3.17
©Silberschatz, Korth and Sudarshan
Query Language (#7, adv. SQL 1)

MySQL 5 不支援 “with” Clause

但可用 “create view” 或 “from (…) as” 兩種方式代替

with MAXP(tpn, tprice) as (select PN, max(price) from SP group by PN)
select SN, PN, Price from SP, MAXP
where SP.PN=MAXP.tpn and SP.price=MAXP.tprice;

create view MAXP as
(select PN as tpn, max(price) as tprice from SP group by PN);
select SN, PN, Price from SP, MAXP
where SP.PN=MAXP.tpn and SP.price=MAXP.tprice;
drop view MAXP;

select SN, PN, Price
from SP,
(select PN as tpn, max(price) as tprice from SP group by PN) as MAXP
where SP.PN=MAXP.tpn and SP.price=MAXP.tprice;
Database System Concepts, 5th Edition, Oct 5, 2006
3.18
©Silberschatz, Korth and Sudarshan
Query Language (#8, adv. SQL 2)

MySQL 5 不支援 “with” Clause

但可用 “create view” 或 “from (…) as” 兩種方式代替

with STA(PN, sprice, sqty) as
(select PN, sum(price*qty), sum(qty) from SP group by PN)
select PN, sprice/sqty as avg_price from STA;

create view STA as
(select PN, sum(price*qty) as sprice, sum(qty) as sqty
from SP group by PN);
select PN, sprice/sqty as avg_price from STA;
drop view STA;

select PN, sprice/sqty as avg_price from
(select PN, sum(price*qty) as sprice, sum(qty) as sqty
from SP group by PN) as STA;
Database System Concepts, 5th Edition, Oct 5, 2006
3.19
©Silberschatz, Korth and Sudarshan
SQL for Relational Database
 Data Definition Language (DDL)

Create table S …

Create view V …

Alter table S…

Drop table S
 Data Manipulation Language (DML)

Insert into S …

Delete from S …

Update S set …
 Query Language

Select – from – where
Database System Concepts, 5th Edition, Oct 5, 2006
3.20
©Silberschatz, Korth and Sudarshan