Information Systems for Engineers Fall Data Definition with SQL

Transcription

1 Ghislain Fourny Information Systems for Engineers Fall Data Definition with SQL Rare Book and Manuscript Library, Columbia University.

2 What does data look like? Relations 2

3 Reminder: relation 0 to many A B 3

4 Reminder: partial function 0 to 1 A B 4

5 Reminder: function exactly 1 A B 5

6 Reminder: the two alternate definitions Definition 1: A table is a relation over its attribute domains. Extension + Domain + a 0 Domain + a 3 Definition 2: A table is a set of partial functions mapping strings to values, and with identical support. Extension + S V s.t. t Extension +, support t = Attributes + 6

7 The two alternate definitions Definition 1: A table is a relation over its attribute domains. Extension + Domain + a 0 Domain + a 3 (Domain integrity is always satisfied by definition) Definition 2: A table is a set of partial functions mapping strings to values, and with identical support. (Domain integrity is defined separately) Extension + S V s.t. t Extension +, support t = Attributes + 7

8 The two alternate definitions Definition 1: A table is a relation over its attribute domains. Extension + Domain + a 0 Domain + a 3 Very popular in database books, but imprecise regarding attribute (non-)order Definition 2: A table is a set of partial functions mapping strings to values, and with identical support. Extension + S V s.t. t Extension +, support t = Attributes + More rigorous, and pedagogically nice to separate definition from domain integrity 8

9 Reminder: definition with partial functions A relation R is made of 1. Attributes Attributes + Attributes + S 9

10 Reminder: definition with partial functions A relation R is made of 1. Attributes Attributes + Attributes + S 2. An extension (set of tuples) Extension + Extension + S V such that: t Extension +, support t = Attributes + 10

11 Domain integrity Given a relation R and a domain constraint Domain + Domain integrity is fulfilled if Attributes + Domain + Extension + a d t Extension +, a Attributes + In other words: t. a Domain + (a) Tuples must have their values in the domains associated with their attributes. t t.a d 11

12 Reminder: definition with relations A relation R is made of Schema +, Domain +, Extension + as follows: Attributes + 1. a set of schema attributes, ordered for convenience (arbitrarily) a 0, a L,..., a 3 12

13 Reminder: definition with relations A relation R is made of Schema +, Domain +, Extension + as follows: 1. a set of schema attributes, ordered for convenience (arbitrarily) Attributes + Domain + a 0, a L,..., a 3 2. a family of domains associated with these attributes (the types) a Domain + (a) 13

14 Reminder: definition with relations A relation R is made of Schema +, Domain +, Extension + as follows: 1. a set of schema attributes, ordered for convenience (arbitrarily) a 0, a L,..., a 3 Attributes + Domain + Extension + 2. a family of domains associated with these attributes (the types) a Domain + (a) 3. a set of tuples (the extension) Extension + Domain + a 0 Domain + a 3 Domain integrity holds by definition. Instead of partial function 14

15 In practice Customer ID Security ID Quantity Integer String Integer 1 CH CH CH CH CH CH This is how database people think. 15

16 SELECT name, mayor WHERE country = "Switzerland" FROM cities SQL 16

17 SQL History Don Chamberlin Raymond Boyce 17

18 The early days (early 1970s) First commercial relational database System R + SEQUEL First commercial relational query language Almaden (San Jose) First customer (1977) 18

19 SEQUEL Structured English QUEry Language Declarative language Set-based (Manipulates entire relations with a single command) 19

20 Renaming SEQUEL (Trademark issue) SQL ESS-kew-EL or SEE-kwəl 20

21 Domain types 21

22 Data types Customer ID Security ID Quantity Integer String Integer 1 CH CH CH CH CH CH

23 Kinds of domains 23

24 Kinds of domains Strings Booleans Numbers Date & Time Enumeration Binary Duration 24

25 Strings "foo" "Zurich" "Ilsebill salzte nach." 25

26 Strings "foo" "Zurich" "Ilsebill salzte nach." f o o Z u r i c h I l s e b i l l s a l z t e n a c h. 26

27 Strings Fixed length 27

28 Strings Fixed length Example: Swiss cantons ZH AG ZG GE BE NE AI AR... 28

29 Strings Fixed length Variable length with limit 29

30 Strings Fixed length Variable length with limit Example: international licence plate country code F D GB CH EIR 30

31 Strings Fixed length Variable length with limit Variable length without limit 31

32 Strings Fixed length Variable length with limit Variable length without limit Example: the content of a webpage on a blog 32

33 Strings Fixed length character(10) Variable length with limit Variable length without limit 33

34 Strings Fixed length character(10) char(10) char Variable length with limit Variable length without limit 34

35 Strings Fixed length Variable length with limit character(10) char(10) char character varying(10) Variable length without limit 35

36 Strings Fixed length Variable length with limit character(10) char(10) char character varying(10) varchar(10) Variable length without limit 36

37 Strings Fixed length Variable length with limit Variable length without limit character(10) char(10) char character varying(10) varchar(10) clob 37

38 Strings Fixed length Variable length with limit Variable length without limit character(10) char(10) char character varying(10) varchar(10) clob text Non-standard varchar Non-standard 38

39 String types: Behavior A B C char(3) varchar(5) text 39

40 String types: Behavior A B C char(3) varchar(5) text 40

41 String types: Behavior f A B C char(3) varchar(5) text 41

42 String types: Behavior f A B C char(3) varchar(5) text f f f 42

43 String types: Behavior f foo A B C char(3) varchar(5) text f f f 43

44 String types: Behavior f foo A B C char(3) varchar(5) text f f f foo foo foo 44

45 String types: Behavior f foo foobar A B C char(3) varchar(5) text f f f foo foo foo 45

46 String types: Behavior f foo foobar A B C char(3) varchar(5) text f f f foo foo foo foobar 46

47 String types: Behavior f foo foobar fo A B C char(3) varchar(5) text f f f foo foo foo foobar 47

48 String types: Behavior f foo foobar fo A B C char(3) varchar(5) text f f f foo foo foo foobar fo fo fo 48

49 String types: Design choices text is not standard Favor varchar(n) char(n) eats up space 49

50 Numbers: Integer types 50

51 Numbers: Integer types Mathematically: Z (A ring with addition and multiplication) 51

52 Lexical space vs. value space Value space Lexical space 52

53 Lexical space vs. value space "1" "01"... Value space Lexical space 53

54 Lexical space vs. value space "4" "04" "100b"... Value space Lexical space 54

55 If you program in Java... 55

56 If you program in Java... byte short int long 56

57 If you program in Java... byte short int long 8 bits 16 bits 32 bits 64 bits 57

58 Numbers: Integer types Small integers to (16 bits) 58

59 Numbers: Integer types Small integers to Integers to (16 bits) (32 bits) 59

60 Numbers: Integer types Small integers to Integers to Big Integers to (16 bits) (32 bits) (64 bits) 60

61 Numbers: Integer types Small integers to Integers to Big Integers to smallint integer int bigint 61

62 Binary numeral system Decimal Binary

63 Binary numeral system 3S0 number = O d Q. 2 Q QTU = d 3S0 d L d 0 d U Decimal Binary

64 Numbers: Arbitrary precision

65 Numbers: Arbitrary precision Precision 32 digits 65

66 Numbers: Arbitrary precision Scale 22 digits 66

67 Numbers: Arbitrary precision types Any precision and scale numeric decimal

68 Numbers: Arbitrary precision types Any precision and scale Limit precision, any scale numeric decimal numeric(32) decimal(32) 68

69 Numbers: Arbitrary precision types Any precision and scale Limit precision, any scale numeric decimal numeric(32) decimal(32) Example: disk capacity

70 Numbers: Arbitrary precision types Any precision and scale Limit precision, any scale Limit precision and scale numeric decimal numeric(32) decimal(32) numeric(32,22) decimal(32,22) 70

71 Numbers: Arbitrary precision types Any precision and scale Limit precision, any scale numeric decimal numeric(32) decimal(32) Limit precision and scale Example: amount of money numeric(32,22) decimal(32,22) 71

72 Arbirary precision types: Behavior 0 A B C numeric numeric(3) numeric(3,1) 72

73 Arbirary precision types: Behavior 0 A B C numeric numeric(3) numeric(3,1)

74 Arbirary precision types: Behavior A B C numeric numeric(3) numeric(3,1)

75 Arbirary precision types: Behavior A B C numeric numeric(3) numeric(3,1)

76 Arbirary precision types: Behavior A B C numeric numeric(3) numeric(3,1)

77 Arbirary precision types: Behavior A B C numeric numeric(3) numeric(3,1)

78 Arbirary precision types: Behavior A B C numeric numeric(3) numeric(3,1)

79 Arbirary precision types: Behavior A B C numeric numeric(3) numeric(3,1)

80 Arbirary precision types: Behavior A B C numeric numeric(3) numeric(3,1)

81 Arbirary precision types: Behavior A B C numeric numeric(3) numeric(3,1)

82 Numbers: Approximate (finite) precision

83 Numbers: Approximate (finite) precision Base 2, canonical x

84 Numbers: Approximate (finite) precision Base 2, canonical x 2 31 Encoding

85 Numbers: Approximate (finite) precision Base 2, canonical x 2 31 Encoding Read back

86 IEEE 754 standard 32 bits ca. 7 digits to single precision 86

87 IEEE 754 standard 32 bits 64 bits ca. 7 digits ca. 15 digits to to single precision double precision 87

88 IEEE 754 types Single precision real float(24) Double precision Arbitrary precision 88

89 IEEE 754 types Single precision real float(24) Double precision double precision float(53) Arbitrary precision 89

90 IEEE 754 types Single precision real float(24) Double precision double precision float(53) Arbitrary precision float(1)... float(24) float(25)... float(53) real double precision Non-standard 90

91 IEEE 754: special values - '-Infinity' 91

92 IEEE 754: special values - + '-Infinity' 'Infinity' 92

93 IEEE 754: special values - + NaN '-Infinity' 'Infinity' 'Nan'! Behavior differs from IEEE754: Equal to itself Higher than all other numbers 93

94 Booleans 94

95 Booleans TRUE FALSE 95

96 Booleans TRUE FALSE t true y yes Non-standard f false n no Non-standard on off

97 Booleans: three-valued logics? TRUE FALSE NULL t true y yes on Non-standard f false n no off Non-standard

98 Boolean type Boolean boolean 98

99 Dates and times Date 99

100 Dates and times Date Time 100

101 Dates and times Date Time Timestamp 101

102 Dates (Gregorian calendar) 102

103 Dates (Gregorian calendar) Year + Month + Day 2017 August 1st (AD) 103

104 Times 104

105 Times Hours + Minutes + Seconds 10 : 31 : Up to the µs (6 decimals) 105

106 Timestamps 106

107 Timestamps Year + Month + Day + Hours + Minutes + Seconds 2017 August 1 st 10 : 31 : (AD) 107

108 Dates and times: types Dates date 108

109 Dates and times: types Dates Times No time zone date time time(3) time without time zone time(5) without time zone 109

110 Dates and times: types Dates Times No time zone With time zone! [usage discouraged] date time time(3) time without time zone time(5) without time zone time with time zone time(1) with time zone 110

111 Dates and times: types Dates Times Timestamps No time zone! [usage discouraged] With time zone No time zone date time time(3) time without time zone time(5) without time zone time with time zone time(1) with time zone timestamp timestamp(6) timestamp without time zone timestamp(4) without time zone 111

112 Dates and times: types Dates Times Timestamps No time zone! [usage discouraged] With time zone No time zone With time zone date time time(3) time without time zone time(5) without time zone time with time zone time(1) with time zone timestamp timestamp(6) timestamp without time zone timestamp(4) without time zone timestamp with time zone timestamp(0) with time zone112

113 Durations 113

114 Duration kinds Year Month Day Hour Minute Second 114

115 Duration kinds Year Month Day Hour Minute Second Example: 2 years and 4 months 115

116 Duration kinds Year Month Day Hour Minute Second Example: 2 years and 4 months 116

117 Duration kinds Year Month Day Hour Minute Second Example: 2 years and 4 months Example: 3 hours and 14 minutes 117

118 Duration kinds Year Month Day Hour Minute Second Example: 2 years and 4 months Example: 3 hours and 14 minutes 118

119 "Duration wall": why not month to days? 2 months and 4 days 119

120 "Duration wall": why not month to days? 2 months and 4 days 2 months and 30 days 2 months and 31 days 3 months Ambiguity zone!! 120

121 Durations: types interval interval(3) Durations 121

122 Durations: types Durations interval interval(3) interval year interval year to month interval month (0) interval day (6) interval day to hour interval day to minute (2) interval day to second interval hour interval hour to minute (5) interval hour to second interval minute interval minute to second (4) interval second 122

123 Binaries

124 Binary content 124

125 Binary content: types Fixed length binary(10) 125

126 Binary content: types Fixed length Variable length with limit binary(10) varbinary(100) 126

127 Binary content: types Fixed length Variable length with limit binary(10) varbinary(100) Variable length without limit blob bytea Non-standard 127

128 Summary of standardized SQL types Kind Types Character char(p) varchar(p) clob 128

129 Summary of standardized SQL types Kind Types Character Binary char(p) varchar(p) clob binary(p) varbinary(p) blob 129

130 Summary of standardized SQL types Kind Types Character Binary Number, exact char(p) varchar(p) clob binary(p) varbinary(p) blob numeric(p,s) decimal(p,s) smallint integer(p) bigint 130

131 Summary of standardized SQL types Kind Types Character Binary Number, exact Number, approximate char(p) varchar(p) clob binary(p) varbinary(p) blob numeric(p,s) decimal(p,s) smallint integer(p) bigint float(p) real double precision 131

132 Summary of standardized SQL types Kind Types Character Binary Number, exact Number, approximate Boolean char(p) varchar(p) clob binary(p) varbinary(p) blob numeric(p,s) decimal(p,s) smallint integer(p) bigint float(p) real double precision boolean 132

133 Summary of standardized SQL types Kind Types Character Binary Number, exact Number, approximate Boolean Date and time char(p) varchar(p) clob binary(p) varbinary(p) blob numeric(p,s) decimal(p,s) smallint integer(p) bigint float(p) real double precision boolean date time time with time zone timestamp timestamp with time zone 133

134 Summary of standardized SQL types Kind Types Character Binary Number, exact Number, approximate Boolean Date and time Intervals char(p) varchar(p) clob binary(p) varbinary(p) blob numeric(p,s) decimal(p,s) smallint integer(p) bigint float(p) real double precision boolean date time time with time zone timestamp timestamp with time zone interval year to month interval day to second 134

135 Creating and dropping tables Vitaly Korovin / 123RF Stock Photo 135

136 DDL on tables + Create a table 136

137 DDL on tables + Create a table * Modify a table 137

138 DDL on tables + Create a table * Modify a table - Drop a table 138

139 Relations (the math, for database scientists) A relation R is made of 1. Attributes Attributes + Attributes + S 2. An extension (set of tuples) Extension + Extension + S V such that: t Extension +, attributes t = Attributes + 139

140 Domain integrity Given a relation R and a domain constraint Domain + Domain integrity is fulfilled if Attributes + Domain + Extension + a d t Extension +, a Attributes + In other words: t. a Domain + (a) Tuples must have their values in the domains associated with their attributes. t t.a d 140

141 Creating a table 141

142 Creating a table + A new table has an empty extension 142

143 Creating a table + So we only specify: - a name - the attributes - the associated domains 143

144 Creating a table: hello, world! CREATE TABLE helloworldtable ( name text ); 144

145 Creating a table: hello, world! CREATE TABLE helloworldtable ( name text ); helloworldtable name text 145

146 Creating a table: more columns CREATE TABLE persons ( first_name varchar(30), middle_initial char(1), last_name text, birth_date date, gender boolean, passportscan bytea ); 146

147 Creating a table: more columns CREATE TABLE persons ( first_name varchar(30), middle_initial char(1), last_name text, birth_date date, gender boolean, passportscan bytea ); persons name middle_initial last_name birth_date gender passport_scan varchar(30) char(1) text date boolean bytea 147

148 Table with no columns CREATE TABLE emptytable (); (because we can?) important for the theory 148

149 Table with no columns (yes) CREATE TABLE emptytable (); (because we can?) important for the theory emptytable 149

150 Dropping a table - We only specify: - the name 150

151 Dropping a table: hello, world! DROP TABLE helloworldtable; helloworldtable name text 151

152 Dropping a table: hello, world! DROP TABLE helloworldtable; helloworldtable name text 152

153 Dropping a non-existing table: error DROP TABLE tablethatdoesntexist; 153

154 Dropping a non-existing table: error DROP TABLE tablethatdoesntexist; 154

155 Silently avoiding errors upon dropping a table DROP TABLE tablethatmayormaynotexist IF EXISTS; 155

156 Populating tables Inserting and deleting tuples Vitaly Korovin / 123RF Stock Photo 156

157 DML on tuples Insert a tuple + 157

158 DML on tuples Insert a tuple + Update a tuple * 158

159 DML on tuples Insert a tuple + Update a tuple * Delete a tuple - 159

160 Inserting tuples helloworldtable name text INSERT INTO helloworldtable VALUES Einstein; 160

161 Inserting tuples helloworldtable name text INSERT INTO helloworldtable VALUES Einstein; helloworldtable name text Einstein 161

162 Inserting tuples: explicit version helloworldtable name text Einstein INSERT INTO helloworldtable (name) VALUES Gödel; 162

163 Inserting tuples: explicit version helloworldtable name text Einstein INSERT INTO helloworldtable (name) VALUES Gödel; helloworldtable name text Einstein Gödel 163

164 Inserting tuples: multiple rows persons name middle_initial last_name birth_date gender passport_scan varchar(30) char(1) text date boolean bytea INSERT INTO persons VALUES ('James', 'T', 'Kirk', DATE ' ', TRUE, E'\\xAD10E7'), ('Beverly', 'C', 'Crusher', DATE ' ', FALSE, E'\\xAD234F7') ; 164

165 Inserting tuples: multiple rows persons name middle_initial last_name birth_date gender passport_scan varchar(30) char(1) text date boolean bytea INSERT INTO persons VALUES ('James', 'T', 'Kirk', DATE ' ', TRUE, E'\\xAD10E7'), ('Beverly', 'C', 'Crusher', DATE ' ', FALSE, E'\\xAD234F7') ; persons name middle_initial last_name birth_date gender passport_scan varchar(30) char(1) text date boolean bytea James T Kirk TRUE AD10E7 Beverly C Crusher FALSE AD234F7 165

166 Inserting tuples: omitting columns and NULL persons name middle_initial last_name birth_date gender passport_scan varchar(30) char(1) text date boolean bytea James T Kirk TRUE AD10E7 Beverly C Crusher FALSE AD234F7 INSERT INTO persons (name, birth_date, gender, passport_scan) VALUES ('Spock', DATE ' ', TRUE, E'\\xAD234F7') ; 166

167 Inserting tuples: omitting columns and NULL persons name middle_initial last_name birth_date gender passport_scan varchar(30) char(1) text date boolean bytea James T Kirk TRUE AD10E7 Beverly C Crusher FALSE AD234F7 INSERT INTO persons (name, birth_date, gender, passport_scan) VALUES ('Spock', DATE ' ', TRUE, E'\\xAD234F7') ; persons name middle_initial last_name birth_date gender passport_scan varchar(30) char(1) text date boolean bytea James T Kirk TRUE AD10E7 Beverly C Crusher FALSE AD234F7 Spock NULL NULL TRUE AD234F7 167

168 NULL By default, domains all contain an additional value NULL 168

169 NULL: interpretations? Not known 169

170 NULL: interpretations? Not known Not applicable 170

171 NULL: interpretations? Not known Not applicable Secret 171

172 Allowing (or not) NULL in a domain CREATE TABLE persons ( first_name varchar(30), middle_initial char(1), last_name text, birth_date date, gender boolean, passportscan bytea ); 172

173 Allowing (or not) NULL in a domain not allowed CREATE TABLE persons ( first_name varchar(30) NOT NULL, middle_initial char(1), last_name text, birth_date date, gender boolean, passportscan bytea ); 173

174 Allowing (or not) NULL in a domain not allowed CREATE TABLE persons ( first_name varchar(30) NOT NULL, middle_initial char(1) NULL, last_name text, birth_date date, allowed (default) gender boolean, passportscan bytea ); 174

175 NULL: best practice CREATE TABLE persons ( first_name varchar(30) NOT NULL, middle_initial char(1) NULL, last_name text NULL, birth_date date NOT NULL, gender boolean NOT NULL, passportscan bytea NOT NULL ); Mark as many columns as possible as not null. 175

176 Updating tuples persons name middle_initial last_name birth_date gender passport_scan varchar(30) char(1) text date boolean bytea James T Kirk TRUE AD10E7 Beverly C Crusher FALSE AD234F7 Spock NULL NULL TRUE AD234F7 UPDATE persons SET last_name = 'Picard' WHERE last_name = 'Crusher'; 176

177 Updating tuples persons name middle_initial last_name birth_date gender passport_scan varchar(30) char(1) text date boolean bytea James T Kirk TRUE AD10E7 Beverly C Crusher FALSE AD234F7 Spock NULL NULL TRUE AD234F7 UPDATE persons SET last_name = 'Picard' WHERE last_name = 'Crusher'; persons name middle_initial last_name birth_date gender passport_scan varchar(30) char(1) text date boolean bytea James T Kirk TRUE AD10E7 Beverly C Picard FALSE AD234F7 Spock NULL NULL TRUE AD234F7 177

178 Removing tuples persons name middle_initial last_name birth_date gender passport_scan varchar(30) char(1) text date boolean bytea James T Kirk TRUE AD10E7 Beverly C Picard FALSE AD234F7 Spock NULL NULL TRUE AD234F7 DELETE FROM persons WHERE name = 'Spock'; 178

179 Removing tuples persons name middle_initial last_name birth_date gender passport_scan varchar(30) char(1) text date boolean bytea James T Kirk TRUE AD10E7 Beverly C Picard FALSE AD234F7 Spock NULL NULL TRUE AD234F7 DELETE FROM persons WHERE name = 'Spock'; persons name middle_initial last_name birth_date gender passport_scan varchar(30) char(1) text date boolean bytea James T Kirk TRUE AD10E7 Beverly C Picard FALSE AD234F7 179

180 Default values CREATE TABLE persons ( first_name varchar(30), middle_initial char(1), last_name text, birth_date date, gender boolean, passportscan bytea ); 180

181 Default values CREATE TABLE persons ( first_name varchar(30), middle_initial char(1) DEFAULT 'N', last_name text DEFAULT 'NONE', birth_date date, gender boolean, passportscan bytea ); 181

182 Default values: inserting tuples persons name middle_initial last_name birth_date gender passport_scan varchar(30) char(1) text date boolean bytea James T Kirk TRUE AD10E7 Beverly C Crusher FALSE AD234F7 INSERT INTO persons (name, birth_date, gender, passport_scan) VALUES ('Spock', DATE ' ', TRUE, E'\\xAD234F7') ; 182

183 Default values: inserting tuples persons name middle_initial last_name birth_date gender passport_scan varchar(30) char(1) text date boolean bytea James T Kirk TRUE AD10E7 Beverly C Crusher FALSE AD234F7 INSERT INTO persons (name, birth_date, gender, passport_scan) VALUES ('Spock', DATE ' ', TRUE, E'\\xAD234F7') ; persons name middle_initial last_name birth_date gender passport_scan varchar(30) char(1) text date boolean bytea James T Kirk TRUE AD10E7 Beverly C Crusher FALSE AD234F7 Spock N NONE TRUE AD234F7 183

184 "Default default values": NULL CREATE TABLE persons ( first_name varchar(30) DEFAULT NULL, middle_initial char(1) DEFAULT 'N', last_name text DEFAULT 'NONE', birth_date date DEFAULT NULL, gender boolean DEFAULT NULL, passportscan bytea DEFAULT NULL ); 184

185 Modify tables Milosh Kojadinovich / 123RF Stock Photo 185

186 DDL on tables + Create a table 186

187 DDL on tables + Create a table * Modify a table 187

188 DDL on tables + Create a table * Modify a table - Drop a table 188

189 Add a column ALTER TABLE helloworldtable ADD COLUMN flag boolean; helloworldtable name text 189

190 Add a column ALTER TABLE helloworldtable ADD COLUMN flag boolean; helloworldtable name text helloworldtable name flag text boolean 190

191 Add a column: default values, null ALTER TABLE helloworldtable ADD COLUMN flag2 boolean not null default true; helloworldtable name flag text boolean 191

192 Add a column: default values, null ALTER TABLE helloworldtable ADD COLUMN flag2 boolean not null default true; helloworldtable name flag text boolean helloworldtable name flag flag2 text boolean boolean 192

193 Rename a column ALTER TABLE helloworldtable RENAME COLUMN flag TO f; helloworldtable name flag text boolean 193

194 Rename a column ALTER TABLE helloworldtable RENAME COLUMN flag TO f; helloworldtable name flag text boolean helloworldtable name f text boolean 194

195 Remove a column ALTER TABLE helloworldtable DROP COLUMN f; helloworldtable name f text boolean 195

196 Remove a column ALTER TABLE helloworldtable DROP COLUMN f; helloworldtable name f text boolean helloworldtable name text 196

197 Rename a table ALTER TABLE helloworldtable RENAME TO table; helloworldtable name text 197

198 Rename a table ALTER TABLE helloworldtable RENAME TO table; helloworldtable name text table name text 198

199 Consistency constraints Milosh Kojadinovich / 123RF Stock Photo 199

200 Consistency constraints There are three fundamental consistency constraints: Not null Check Unique 200

201 Not null (already covered) CREATE TABLE persons ( name text NOT NULL, student boolean ); 201

202 Not null (already covered) not allowed CREATE TABLE persons ( name text NOT NULL, student boolean ); allowed (default) 202

203 Not null (already covered) not allowed CREATE TABLE persons ( name text NOT NULL, student boolean ); allowed (default) persons name text foobar NULL student boolean NULL TRUE 203

204 Check CREATE TABLE persons ( name text check (foo <> 'Spock'), student boolean ); 204

205 Check CREATE TABLE persons ( name text check (foo <> 'Spock'), student boolean ); persons name text foobar Spock student boolean NULL TRUE 205

206 Unique CREATE TABLE persons ( name text UNIQUE, student boolean, ahv varchar(13) UNIQUE, ); 206

207 Unique CREATE TABLE persons ( name text UNIQUE, student boolean, ahv varchar(13) UNIQUE, ); persons name student ahv text boolean varchar(13) foobar NULL Spock TRUE Spock TRUE

208 Primary keys Sergey Nivens / 123RF Stock Photo 208

209 Primary key persons ahv varchar(13) name text Albert Einstein Kurt Gödel Alan Turing 209

210 Primary key persons ahv varchar(13) name text Albert Einstein Kurt Gödel Alan Turing A primary key uniquely identifies a row 210

211 Primary key persons ahv varchar(13) name text Albert Einstein Kurt Gödel NULL Alan Turing Can't be NULL 211

212 Primary keys persons ahv varchar(13) name text Albert Einstein Kurt Gödel NULL Alan Turing Must be unique 212

213 Primary key: first idea CREATE TABLE persons ( ahv varchar(13) UNIQUE NOT NULL, name text ); 213

214 Primary key: first idea CREATE TABLE persons ( ahv varchar(13) UNIQUE NOT NULL, name text ); persons ahv varchar(13) name text Albert Einstein Kurt Gödel Alan Turing 214

215 Primary key: there is more to it persons ahv varchar(13) name text Albert Einstein Kurt Gödel Alan Turing Niklaus Wirth Isaac Newton Srinivasa Ramanujan Pythagoras Thales Alonso Church 215

216 Primary key: there is more to it persons ahv varchar(13) name text Albert Einstein Kurt Gödel We want to quickly retrieve a row with its key Alan Turing Niklaus Wirth Isaac Newton Srinivasa Ramanujan Pythagoras Thales Alonso Church (We won't say how just yet) 216

217 Primary key: syntax CREATE TABLE persons ( ahv varchar(13) PRIMARY KEY, name text ); persons ahv varchar(13) name text Albert Einstein Kurt Gödel Alan Turing 217

218 Primary key: alternate syntax CREATE TABLE persons ( ahv varchar(13), name text, PRIMARY KEY(ahv) ); persons ahv varchar(13) name text Albert Einstein Kurt Gödel Alan Turing 218

219 Primary key: compound keys CREATE TABLE persons ( first text, last text, city text, PRIMARY KEY(first, last) ); 219

220 Primary key: compound keys CREATE TABLE persons ( first text, last text, city text, PRIMARY KEY(first, last) ); persons first last city text text text Albert Einstein Zurich Kurt Gödel Berlin Kurt Turing London 220

221 Foreign key taxes ahv varchar(13) fiscal residence char(2) CH AT GB 221

222 Foreign key taxes ahv varchar(13) fiscal residence char(2) CH AT GB persons ahv varchar(13) name text Albert Einstein Kurt Gödel Alan Turing 222

223 Foreign key taxes ahv varchar(13) fiscal residence char(2) CH AT GB CREATE TABLE taxes ( ahv varchar(13) REFERENCES persons (ahv), fiscal residence char(2) ); Can be any column (not necessary primary key, but must be UNIQUE) 223

224 Foreign key: no column specified means primary key taxes ahv varchar(13) fiscal residence char(2) CH AT GB CREATE TABLE persons ( ahv varchar(13) REFERENCES persons, fiscal residence char(2) ); 224

225 Foreign key: duplicate references allowed taxes ahv varchar(13) fiscal residence char(2) CH AT GB US CREATE TABLE persons ( ahv varchar(13) REFERENCES persons, fiscal residence char(2) ); 225

226 Foreign key: compound keys persons first last city text text text taxes first last course text text text Albert Einstein Zurich Kurt Gödel Berlin Srinivasa Ramanujan London Albert Einstein Relativity Kurt Gödel Completeness Srinivasa Ramanujan Taxi numbers Srinivasa Ramanujan Formulas 226

227 Foreign key: compound keys persons first last city text text text taxes first last course text text text Albert Einstein Zurich Kurt Gödel Berlin Srinivasa Ramanujan London Albert Einstein Relativity Kurt Gödel Completeness Srinivasa Ramanujan Taxi numbers Srinivasa Ramanujan Formulas CREATE TABLE persons ( first text, last text, course text, FOREIGN KEY (first, last) REFERENCES persons (first, last) ); 227

228 Foreign key: NULL references are allowed persons first last city text text text taxes first last course text text text Albert Einstein Zurich Kurt Gödel Berlin Srinivasa Ramanujan London Albert Einstein Relativity Kurt Gödel Completeness Srinivasa Ramanujan Taxi numbers NULL NULL Formulas CREATE TABLE persons ( first text, last text, course text, FOREIGN KEY (first, last) REFERENCES persons (first, last) ); 228

229 Deletion of referenced values persons first last city text text text DELETE Albert Einstein Zurich Kurt Gödel Berlin Srinivasa Ramanujan London 229

230 Deletion of referenced values persons first last city text text text DELETE Albert Einstein Zurich Kurt Gödel Berlin Srinivasa Ramanujan London taxes first last course text text text Albert Einstein Relativity Kurt Gödel Completeness Srinivasa Ramanujan Taxi numbers Srinivasa Ramanujan Formulas What do we do here? 230

231 Deletion: cascading FOREIGN KEY (first, last) REFERENCES persons (first, last) ON DELETE CASCADE persons first last city text text text Albert Einstein Zurich Kurt Gödel Berlin Srinivasa Ramanujan London 231

232 Deletion: cascading FOREIGN KEY (first, last) REFERENCES persons (first, last) ON DELETE CASCADE persons first last city text text text Albert Einstein Zurich Kurt Gödel Berlin Srinivasa Ramanujan London taxes first last course text text text Albert Einstein Relativity Kurt Gödel Completeness Srinivasa Ramanujan Taxi numbers Srinivasa Ramanujan Formulas 232

233 Deletion: restricting FOREIGN KEY (first, last) REFERENCES persons (first, last) ON DELETE RESTRICT persons first last city text text text Albert Einstein Zurich Kurt Gödel Berlin Srinivasa Ramanujan London 233

234 Deletion: restricting FOREIGN KEY (first, last) REFERENCES persons (first, last) ON DELETE RESTRICT "I'm sorry, Dave. I'm afraid I can't do that." persons first last city text text text Albert Einstein Zurich Kurt Gödel Berlin Srinivasa Ramanujan London taxes first last course text text text Albert Einstein Relativity Kurt Gödel Completeness Srinivasa Ramanujan Taxi numbers Srinivasa Ramanujan Formulas 234

235 Deletion: set to NULL FOREIGN KEY (first, last) REFERENCES persons (first, last) ON DELETE SET NULL persons first last city text text text Albert Einstein Zurich Kurt Gödel Berlin Srinivasa Ramanujan London 235

236 Deletion: set to NULL FOREIGN KEY (first, last) REFERENCES persons (first, last) ON DELETE SET NULL persons first last city text text text Albert Einstein Zurich Kurt Gödel Berlin Srinivasa Ramanujan London taxes first last course text text text Albert Einstein Relativity NULL NULL Completeness Srinivasa Ramanujan Taxi numbers Srinivasa Ramanujan Formulas 236

237 Deletion: set to default value FOREIGN KEY (first, last) REFERENCES persons (first, last) ON DELETE SET DEFAULT persons first last city text text text Albert Einstein Zurich Kurt Gödel Berlin Srinivasa Ramanujan London 237

238 Deletion: set to default value FOREIGN KEY (first, last) REFERENCES persons (first, last) ON DELETE SET DEFAULT persons first last city text text text Albert Einstein Zurich Kurt Gödel Berlin Srinivasa Ramanujan London taxes first last course text text text Albert Einstein Relativity Albert Einstein Completeness Srinivasa Ramanujan Taxi numbers Srinivasa Ramanujan Formulas 238