SQL и Реляционная Теория

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...................................................... 142 .................................................................. 145........................................................................... 149 ............................................................................... 149 ............................................................................ 151, ........................................ 155 ?............................... 157 .................................... 157 ? ..................................... 159 SQL .................................. 160 ..................................................... 161 ................................................. 165 ........................................................................... 167

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7. SQL II: ........................................................ 171

................................................ 171 ........................................................................... 172 - .................................................................. 174 ................................................................................. 177 ............................................................. 179 - ..................................................... 183 ............................................................................. 185 ................................................................... 190 .......................................... 191 ................................................................. 193 ORDER BY? ......................................................... 194 ........................................................................... 195

8. SQL .................................... 200 ................................................................... 201 ........................................................ 204 SQL ........................................................... 205 ........................................................ 206 SQL ............................................... 210 ............................................................................ 211 .............................................. 213 ? ............................................ 216 ........................................................ 219 ................................................................................... 221 ........................................................................... 223

9. SQL ..................................................... 228 - .............................. 229 ..................................................... 233 .................................................................. 234 .................................................. 236 .............................................................. 240 ? ................................................... 244 ................................................................... 245 ........................................................................... 247

10. SQL ............................................ 250 .......................................... 251 ............................................... 254

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...................................................................... 256 .......................................................... 260 ............................................................. 267 ......................................................... 274 ..................................................... 277 ........................................................................... 278

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........................................... 282 1. ........................................... 284 2. .............................. 285 3. ........................... 286 4. ................................... 288 5. ....................................... 290 6. ............................. 293 7. ..................................... 294 8. COUNT ............................................. 296 9. ............................................. 297 10. UNIQUE .................................................... 298 11. ALL ANY ....................................... 299 12. GROUP BY HAVING ............................................. 303 ........................................................................... 304

12. , SQL ........................... 306SELECT * ............................................................................... 307 ....................................................................... 307 ................................................................ 307 ............................................................... 308 ............................................................................ 311 .................... 314 .................................................................. 315- SQL ............................. 315 ........................................................................... 318

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. - , SNO PNO, - THE_, SNO PNO ( ), -1. , THE_ - SNO PNO THE_SC THE_PC . S.SNO P.PNO , , , . - :

THE_SC ( S.SNO ) = THE_PC ( P.PNO )

: , - .

, , , - THE_, : () () . , -, . -, ; , ( , - , ).

, , , , - . -

1 - , SQL , ( ) - THE_ SQL , , THE_ SQL . , THE_; . - POINT ?.

58 2.

, - , () - () , ( ). , - , -, ; - , , - , , . -, , :

P.WEIGHT * SP.QTY

P.WEIGHT + SP.QTY

, -, ( , , ). , , , - ( ?).

, - (=). - . , -, , . , (. ?), - = , ! , T v, , v - , T.

, = : v1 v2 , - v1 = v2 TRUE, v1 v2 , FALSE . (, v1 v2 , v1 = v2 , v1 v2 , v1 v2.)

, , - , . ( 1). - 1 , 1 , - ( ) - , , -

59

. -: ?

6 (The Relational Model for Data-base Management Version 2) - , - ( ). - , / . , - ? ? LIKE, SUBSTR (), || () , , -. ? ?

, -, :

, - ( , , - , , , , -).

, - .

, // // .

.

. . 2.1. R1 - ; -, - - , - SNO/PNO. , , , R1 .

, R1 R2, -, - - ( PNO R2, , -, -). , R2 1; - , , , -, 1 ( , ?).

60 2.

SNO PNO

R1

S2 P1S2 P2S3 P2S4 P2S4 P4

SNO PNO

R2

S2 P1, P2S3 P2

SNO PNO_SET

R3

S2 {P1, P2}S3 {P2}

S4 P5

S4 P2, P4, P5 S4 {P2, P4, P5}

. 2.1. R1, R2 R3

, , R2 1. R2 R3. , R3 1! ( , , , , . , -, . R3 -.) :

-, , PNO_SET -, PNO_SET, , , - : -, , - .

- ( , -), , {P2,P4,P5}, - , , . , , . , 1, , , - .

, ; , . - , , , . , . (-, , ) - : , (, ), . , -, , -. , .

61

R3. . 2.1 PNO_SET . -, (. . 2.2, - PNO_REL). ? , , 1. , - , , . . , - ( , ) , !

PNO_REL . 2.2 , - (relation valued attribute RVA). - RVA- 7, , SQL . (, , - RVA-, -. , SQL -, - , - , - , . -, , , - , SQL- - , , - SQL.

. , RVA- , - , , -. - ; (, , ), , , , , - , , , XML- , . , , , .

, , - ,

1 , , , - , , . , , , , , .

62 2.

, , - . - , - . , -: - ( , , ), , , -. , - - , , .

SNOR4

S2

PNO_REL

PNO

P1P2

PNO

P2P4P5

S4

S3 PNO

P2

. 2.2. R4 ( R3)

? , . ? , - 1 , : - , , -, XML-, - . . :

, - , , . : - , ( ). , , . , -, , , ? -

1 , , . : .

? 63

, , , , -, , . , , , - , .

, , , - , . , , -, V T, , v, V, - T.

, , , - ( , ). ,

( a / b ) + ( x - y )

+, .

, , , - , , , - , - . Op T , Op T.1 , - ; ; XML- - XPath-; -. (:=) (=). , , - , -, , - - , . -

1 -. : , T, - T, T. , , SNO CHAR, , ; , (||) SNO. ( -, .)

64 2.

: , .

, , , , -. , , INTEGER:

:=, - .

=, ,

? 65

, POINT -. Tutorial D - SQL, SQL - , -, REFLECT, P - (x, y) - ( x, y):

1 OPERATOR REFLECT ( P POINT ) RETURNS POINT ; 2 RETURN POINT ( - THE_X ( P ) , - THE_Y ( P ) ) ; 3 END OPERATOR ;

:

1 , REFLECT, - P POINT POINT ( , - POINT).

2 , . RETURN. , POINT; - , X Y . - THE_; X Y -, P, - , 1.

3 .

, . - , - , . , INTEGER , , - , - :=, =, + . . ( -, , ).

. -, , , , -

1 , : (. 2.5 - ). , POINT, - , ( , ).

66 2.

. , -, ( , - , ); , POINT(X,Y), POINT(1.0,2.5) POINT, POINT . , - , . (, , , - .)

. - , , - , . , , , , T , - T. :

INTEGER ; , , . . INTEGER , .

; ; , -, . . -.

, . , , , -, -. - - . - ( ); , , - , , - , , .

. Tutorial D - S (); , :

1 VAR S BASE 2 RELATION { SNO CHAR , SNAME CHAR , STATUS INTEGER , CITY CHAR } 3 KEY { SNO } ;

67

:

VAR 1 , - S, BASE , - - .

2 . RELATION , ; - , (, 1 , -/-). , , . .

3 , {SNO} -- .

, , :

RELATION { SNO CHAR , SNAME CHAR , STATUS INTEGER , CITY CHAR }

. - , ( RELATION). , ; - () ( ) () , . , - ARRAY, - . - TUPLE RELATION. - TUPLE:

VAR S_TUPLE TUPLE { STATUS INTEGER , SNO CHAR , CITY CHAR , SNAME CHAR } ;

S_TUPLE , - S ( - , , ). , , , ( , S1), - - S, - , , - S_TUPLE. Tutorial D - :

S_TUPLE := TUPLE FROM ( S WHERE SNO = S1 ) ;

: . -, S_TUPLE, , - , -

68 2.

, , - . : - , . A .

, ( ) t r, t. : t , r ( -).

:

, - ( ), , - . - , . ( - 1.)

, , , ( - ). . - THE_ ; , ( - , THE_ - ).

. - ; , , .

SQL SQL. , 1:

BOOLEAN NUMERIC(p,q) DATECHARACTER(n) DECIMAL(p,q) TIMECHARACTER VARYING(n) INTEGER TIMESTAMPFLOAT(p) SMALLINT INTERVAL

1 , , - .

SQL 69

, - , : CHAR CHARACTER, VARCHAR CHARACTER VARYING, INT INTEGER; - , , SQL, Tutorial D, , - . :

, - . : , , - , THE_.

. :

SET = ;

- (, FETCH). : , , ref exp reference () expression () .

- 1. - (, -, , ).

BOOLEAN , - SQL, - , -. , - WHERE, ON HAVING, BOOLEAN . BOOLEAN, . .

, - (CLOB), (BLOB), (NCHAR . .) ( , XML). .

1 , . -, CHAR VARCHAR = TRUE, , , (. SQL). , , CHAR VARCHAR, = TRUE, ; , , null ( ).

70 2.

, , SQL , , SQL , - , - . , , , - ( ).

SQLSQL ( -, ). :

BOOLEAN BOOLEAN BOOLEAN.

- - ( - CHAR VARCHAR).

( - FLOAT, NUMERIC, DECIMAL, INTEGER SMALLINT).

, , - , .

, . , , INTEGER FLOAT ( INTEGER FLOAT -). - : , . SQL : -, , , ! , , SQL- T1 T2, . 2.3. , - X T1 INTEGER, T2 NUMERIC(5,1), Y T1 NUMERIC(5,1), T2 INTEGER. SQL-:

SELECT X , Y FROM T1 UNION SELECT X , Y FROM T2

SQL 71

. 2.3, X Y - (. ) NUMERIC(5,1), INTEGER NUMERIC(5,1). , - , T1, T2, -, - .1

X

00

T1 Y

1.02.0

X

0.00.0

T2 Y

01

1.0 2

X

0.00.00.01.0

Y

1.02.00.02.0

. 2.3.

: - . ( , , SQL -.) - SQL -; - , , . - , - CAST . ( - UNION):

SELECT CAST ( X AS NUMERIC(5,1) ) AS X , Y FROM T1 UNION SELECT X , CAST ( Y AS NUMERIC(5,1) ) AS Y FROM T2

, -, , SQL, . ( , , .) :

tx - , , t, -

1 , , , -, . , , , . SQL , , , , , -, (UNION), , - ( ), , - , , SQL , .

72 2.

tx, r, t r. : SQL- . 12, , , - .

tx , , t, tx, , v, t - , v. : , , - SQL (. 7).

rx rx sq - ALL ANY ( , >ALL

SQL 73

S. C : - a < b, a = b a > b TRUE, FALSE ( C).

. . , - PAD SPACE ( ) NO PAD ( -). , AB AB ( - ) - . , -, , PAD SPACE. : PAD SPACE, - NO PAD. (, , PAD SPACE / NO PAD , - .)

, a = b - TRUE , a b . , CASE_INSENSITIVE, -. , , - .

, , SQL v1 = v2 TRUE , v1 v2 (, -, ). - , . , - , , (-, MATCH, LIKE, UNIQUE, UNION JOIN), , . -, CASE_INSENSITIVE PAD SPACE. , PNO P SP - P PNO P2, - SP p2 , - SP P, - p .

, , -, UNION, INTERSECT, EXCEPT, JOIN, GROUP BY DISTINCT, , , - . , SQL - . - SQL, - , SQL -

74 2.

, ; , - . , Z T CASE_INSENSITIVE, SELECT MAX(Z) FROM T ZZZ, zzz, T .

SQL, , - ( - 12). , - (. 8), ( - , ). , , - SELECT , - ! : - .

SQL - :

VAR S_TUPLE TUPLE { STATUS INTEGER , SNO CHAR , CITY CHAR , SNAME CHAR } ;

, TUPLE{...} - TUPLE. SQL ROW ( ). SQL :

DECLARE S_ROW /* SQL */ ROW ( SNO VARCHAR(5) , SNAME VARCHAR(25) , STATUS INTEGER , CITY VARCHAR(20) ) ;

, SQL 1; 24 (= 4 * 3 * 2 * 1) , (!).

SQL . , , - Tu to rial D:

1 , SQL , ROW ( ), - , .

SQL 75

SET S_ROW = ( S WHERE SNO = S1 ) ;

, , , , , (. SQL).

SQL- UPDATE (. 3).

: , SQL ( ) TABLE! - RELATION, . CREATE TABLE - , -. , , - :

VAR S BASE RELATION { SNO CHAR , SNAME CHAR , STATUS INTEGER , CITY CHAR } KEY { SNO } ;

SQL:

CREATE TABLE S ( SNO VARCHAR(5) NOT NULL , SNAME VARCHAR(25) NOT NULL , STATUS INTEGER NOT NULL , CITY VARCHAR(20) NOT NULL , UNIQUE ( SNO ) ) ;

, , TABLE. ( , -, UNIQUE(SNO) - , , SNO SNAME.) - - S ( SQL), , ROW (SNO VARCHAR(5), SNAME VARCHAR(25), STATUS INTEGER, CITY VARCHAR(20)).

- , SQL , - . , -, TT , - T, TT, - T ! ,

76 2.

, SQL , 1. , , - , . -, , , , - SQL; , - , ( REF). , , SQL; , - - . : -, , .

, SQL - . . , , ; , - , - . , , - ! - , , , , , , ( 1, , , ).

, : , -, , . -, , , . , - , , ( , -

1 , , . - ( , ), - , -. : () V, V V; () v ( ), - v , - v ( ).

77

). , , -, . , : .

, , - , - . , , , , .

, , . , . - , r T, r T ( !). - . - , ; - - , . ( - , - .) , , .

2.1. ? -

?

2.2. ? ?

2.3. THE_?

2.4. : - ?

2.5. ( 1, - ), :

78 2.

, -.

2.6. ? ?

2.7. -?

2.8. ?

2.9. . , ?

2.10. X . X? , X - ?

2.11. - REFLECT ( ?) , - Tutorial D , .

2.12. Tutorial D , x y - f(x) g(y), f g .

2.13. . - , - - - .

2.14. Tutorial D SQL - - P SP - . SQL, Tutorial D, , -. , - P ( -) ?

2.15. , - 1 (. 1.1) - :

DNO : DNO DNAME : NAME

79

BUDGET : MONEY ENO : ENO ENAME : NAME SALARY : MONEY

, LOCATION CITY ( ). ? , , ; , .

a. LOCATION = London

b. ENAME = DNAME

c. SALARY * 5

d. BUDGET + 50000

e. ENO > E2

f. ENAME || DNAME

g. LOCATION || burg

2.16. , - . , - -, - . .

2.17. , . , , . ? SQL?

2.18. - = . , SQL , = ( , , , - ), , -, . ?

2.19. , , v1 = v2 TRUE - , Op v1 - Op v2 Op. , - SQL . -? ?

2.20. -?

80 2.

2.21. , , v V V = v TRUE (. 5). SQL ( -). ? - ?

2.22. , , - ?

2.23. SQL- SELECT, - , , , , . ?

2.24. , - RVA- - .

2.25. ?

2.25. , = . SQL?

3. ,

- , , , . . , SQL ( ) , - SQL . , , , - . , - , , .

? ?

SNO

S1

SNAME

Smith

STATUS INTEGER

20

CITY CHAR

London

CHAR CHAR

, , ( - , , ). 1 , - , . , - , - ( ?):

82 3. ,

STATUS INTEGER

20

SNAME

Smith

CITY CHAR

London

SNO

S1

CHAR CHAR

, , , , , . , - , :

: T1, T2, ..., Tn (n 0), . - Ti Ai; n -/- . - vi Ti; n / - . , n - , t, - ( -) A1, A2, ..., An. n - t; 1 , 2 , 3 -, , , n n-. , n , - t.

, , S1, :

: 4. , 4.

: CHAR, CHAR, INTEGER, CHAR.

: SNO, SNAME, STATUS, CITY.

: S1, Smith, 20, London. , , - ; , , , .

, - 2, SNO SNO ( -), CHAR. , SNO S1 S1; - SNO(S1). SNO SNO, CHAR! , , - . (, 2 , SNO(S1) SNO.)

? 83

: :

SNO SNAME STATUS INTEGER CITY CHARCHAR CHAR

, - . :

SNOSNAMESTATUS INTEGER CITY CHARCHAR CHAR

: , ? (: 4 * 3 * 2 * 1 = 24)

, ; , , ( 2), , , . Tutorial D TUPLE{H}, {H} -. , :

TUPLE { SNO CHAR , SNAME CHAR , STATUS INTEGER , CITY CHAR }

( ).

: . , -, - (-, , ). (- Tutorial D):

TUPLE { SNO S1 , SNAME Smith , STATUS 20 , CITY London }

( ). , Tutorial D -/-, ; , .

( , , ):

TUPLE { SNO SX , SNAME James , STATUS STX , CITY SCX }

, SX, STX SCX CHAR, INTEGER CHAR .

, Tutorial D TUPLE, - -/, -, . -, TUPLE Tutorial D : , , , . -

84 3. ,

RELATION (. ).

, - . null-. , , , - ( ) , , 1, null , SQL , , null-. : - null- , , null1.

, null-, ; , null-. - .

-, . (: - A A B, , A B , , . , - , . , -.) - S1, , {SNO,CITY} , ( 2):

SNO CITY CHAR

S1 London

CHAR

, TUPLE {SNO CHAR, CITY CHAR}. :

SNO CHAR

S1

1 , - null- . . .

85

1 TUPLE {SNO CHAR}. , - S1, - . Tutorial D - SNO FROM t ( t , - SNO). SQL - : t.SNO. : 2 , - t r, t -, . , v t, , ; , .

, , - . , , , , , - , - . TUPLE{} ( ); 0-, , 0. . , , , , , , . TABLE_DUM TABLE_DEE.

, , . (, 2 , - = , .) , , ( , , ). , , - , - . :

: tx ty , A1, A2, ..., An , i (i = 1, 2, ..., n) vx Ai tx vy Ai ty.

( , - -), , .

, , 0- - . - 0-, - 0-.

86 3. ,

, , -. , (-, ), - .

SQL SQL , ; , - , - , -, TUPLE Tutorial D. ( , - , 2.) - , , , : . -, ROW(1,2) ROW(2,1) - , SQL -. : ROW - SQL .

- SQL ( ) , . , , ( -, SQL ):

( S1 , Smith , 20 , London )

, ( ) - Smith; , SNAME, , .

, SQL , 0- .

2, SQL - 1. , ( -) SQL- UPDATE. , - UPDATE

UPDATE S SET STATUS = 20 , CITY = London WHERE CITY = Paris ;

1 , , , . - SQL .

SQL 87

( ):

UPDATE SSET ( STATUS , CITY ) = ( 20 , London ) WHERE CITY = Paris ;

, - SQL, ( , ) - , , -. SELECT, WHERE - :

SELECT SNO FROM S WHERE ( STATUS , CITY ) = ( 20 , London )

SELECT :

SELECT SNO FROM S WHERE STATUS = 20 AND CITY = London

SELECT SNO FROM S WHERE ( STATUS , CITY ) ( 20 , London )

:

SELECT SNO FROM S WHERE STATUS 20 OR CITY London

OR !

, , SQL , -:

SELECT SNO FROM S WHERE ( STATUS , CITY ) > ( 20 , London )

:

SELECT SNO FROM S WHERE STATUS > 20 OR ( STATUS = 20 AND CITY > London )

- 1, :

88 3. ,

SELECT SNO FROM S WHERE ( STATUS ) = ( 20 )

. - , , :

SELECT SNO FROM S WHERE STATUS = 20

WHERE - (STATUS 20 ). , , SQL , , ; - STATUS = 20 - ( ).

: ( ), =; , , - , . ( , - SQL, - , .)

? . :

SNO SNAME STATUS INTEGER CITY CHAR

S1 Smith 20 LondonS2 Jones 10 ParisS3 Blake 30 ParisS4 Clark 20 LondonS5 Adams 30 Athens

CHAR CHAR

:

: {H} , t1, t2, ..., tm (m 0) {H}. r, {H} {t1, t2, ..., tm}, - ( ) A1, A2, ..., An, A1, A2, ..., An , - {H}. r {H}; r - (, , ),

? 89

. r {t1, t2, ..., tm}. m r.

- . , , . , n- (relationship) n ( - ), , - (relation). , - , (relating) - , - . , , - , .

, , , , . Tutorial D RELATION{H}, {H} , :

RELATION { SNO CHAR , SNAME CHAR , STATUS INTEGER , CITY CHAR }

( .) , - - - , :

RELATION { TUPLE { SNO S1 , SNAME Smith , STATUS 20 , CITY London } , TUPLE { SNO S2 , SNAME Jones , STATUS 10 , CITY Paris } , TUPLE { SNO S3 , SNAME Blake , STATUS 30 , CITY Paris } , TUPLE { SNO S4 , SNAME Clark , STATUS 20 , CITY London } , TUPLE { SNO S5 , SNAME Adams , STATUS 30 , CITY Athens } }

. ( , ):

RELATION { tx1 , tx2 , tx3 }

, tx1, tx2 tx3 - . , Tutorial D RELATION, - .

, , 1, , , . , -, :

90 3. ,

-, (), - .

null-, - , , , - null-.

, , . .

: ( , ). , - , ( - ). , , . - - SP , -, ( - , - ; , - ):

SNO PNO QTY

, , , . -, ( , ).

, :

SNO

S1

PNO

P1

QTY

300

(- , 1). , - . Tutorial D - TUPLE FROM rx ( rx , - 1, RELATION {TUPLE {SNO S1, PNO P1, QTY 300}}, - ). , SQL

n- 91

: () tx , - ( , ), () , t, tx, r () - r. :

SET S_ROW = ( S WHERE SNO = S1 ) ;

, t - r. Tutorial D :

t r

TRUE, t r, FALSE . - , t r t r. , , , SQL- IN , SQL IN , , - ( ). ( , - ):

SELECT SNO , SNAME , STATUS , CITY FROM SWHERE SNO IN ( SELECT SNO FROM SP )

n- , , . ( , .) , - , . , 1 , , , - - . , , - -, .

, , , - , , . . r n , r - n- ( ). , 4-

92 3. ,

, -. , n-, .1 ( ): - .

, , =; , - rx ry T, , , - , . - ; , , - rx ry ( , , - rx, ry) - ry ( , rx, - ry, ry , - rx). - Tutorial D:

S { CITY } = P { CITY }

CITY, - CITY, TRUE, , FALSE . -, ( ) : , , , .

:

S { SNO } SP { SNO }

. : , -?

(-), () ( ). - = rx - ; , , rx. :

IS_EMPTY ( rx )

, TRUE, , rx, , FALSE -

1 , , - ( , - ), , , .

TABLE_DUM TABLE_DEE 93

. - ( 8). :

IS_NOT_EMPTY ( rx )

NOT (IS_EMPTY(rx)).

TABLE_DUM TABLE_DEE , , , -, , ( 0-), , , . , , , ? RELATION{}, .

, r 0. - ? : . -, r ( ) , . -, r , 0-. 0-! , , 0- - , r . - , -: , . ( , , - -).

? , . , ? ( , , ), - ? , , , : TABLE_DUM TABLE_DEE, DUM DEE (DUM , DEE ).1 : FALSE () DUM

1 , . -, , -, , : Tweedledum Tweedledee , ( . -- --). -, , , , , ! , - .

94 3. ,

TRUE () DEE. . : 5 6.

, , , : DEE yes E, DUM no .

- DUM DEE, . , : ( TABLE_DEE) , - . , ; , ( , ). , TABLE_DEE. SQL SQL 0-, , ( -), TABLE_DUM TABLE_DEE.

SQL

SQL, (, CREATE TABLE). 5.

2 , SQL ; SQL ( , ), . , SQL , RELATION, - , , ARRAY, MULTISET - 3 ROW. , - , - - . :

VALUES ( 1, 2 ), ( 2, 1 ), ( 1, 1 ), ( 1, 2 )

( - , SQL ) - ! . . , SQL- ; , - ( ) , .

- :

SQL 95

VALUES ( S1 , Smith , 20 , London ) , ( S2 , Jones , 10 , Paris ) , ( S3 , Blake , 30 , Paris ) , ( S4 , Clark , 20 , London ) , ( S5 , Adams , 30 , Athens )

, , ( -, , - - S, . 1.3), :

1. , VALUES, , . ( -, i- - - , , - i- ).

2. , .

, . , SQL, , - , - (, ). -, , - (?) .

? - , 5 7. , SQL , . , , SQL:

NOT EXISTS ( SELECT CITY FROM S EXCEPT SELECT CITY FROM P ) AND NOT EXISTS ( SELECT CITY FROM P EXCEPT SELECT CITY FROM S )

S{SNO} SP{SNO}:

EXISTS ( SELECT SNO FROM S EXCEPT SELECT SNO FROM SP ) ANDNOT EXISTS ( SELECT SNO FROM SP EXCEPT SELECT SNO FROM S )

96 3. ,

SQL () ( ) () ( ). SQL , . -, , , CREATE TABLE CREATE VIEW , - 1. : AS, , () () . :

SELECT DISTINCT SNAME , Supplier AS TAG FROM S

SELECT DISTINCT SNAME , 2 * STATUS AS DOUBLE_STATUS FROM S

SELECT MAX ( WEIGHT ) AS MBW FROM P WHERE COLOR = Blue

CREATE VIEW SDS AS SELECT DISTINCT SNAME , 2 * STATUS AS DOUBLE_STATUS FROM S ;

SELECT DISTINCT S.CITY AS SCITY , P.CITY AS PCITY FROM S , SP , P WHERE S.SNO = SP.SNO AND SP.PNO = P.PNO

SELECT TEMP.* FROM ( S JOIN P ON S.CITY > P.CITY ) AS TEMP ( SNO , SNAME , STATUS , SCITY , PNO , PNAME , COLOR , WEIGHT , PCITY )

, , . , -

1 , SQL -. , - ; , , , -, . , -, (. 12). , , .

SQL 97

(, WHERE HAVING) :

SELECT MAX ( WEIGHT ) FROM P WHERE COLOR = Blue

, , VALUES.

: , - . -, 6 , UNION , - (, , ); . - , -, ! , SQL , SQL. : - , . ( - , , SNO, , , SNO SNUM .) , - , .

, -, , . , , - EMP, , - . - -, ENO MNO. - , :

( SELECT ENO , MNO FROM EMP ) AS TEMP1 NATURAL JOIN ( SELECT ENO AS MNO , ... FROM EMP ) AS TEMP2/* ... EMP, ENO MNO */

SQL , - , - ( , - - ). - :

- , , - .

98 3. ,

, - .

, (, , , ).

, , SQL . (, SQL - .) , , SQL - , ( ); . : SQL , . , SQL - , :

SELECT *

JOIN, UNION, INTERSECT, EXCEPT , CORRESPONDING (. 6)

, , - (range variable) (. 12)

, , CREATE VIEW (. 9)

INSERT,

ALL ANY, 1 (. 11)

VALUES

. , , , , , . , , , - , ( , - TABLE_DUM TABLE_DEE). , SQL , . ( , ) SQL. .

99

3.1. , ,

, , , , .

3.2. , , : () , () .

3.3. Tutorial D () - -, () - . - SQL, .

3.4. Tutorial D - . SQL, .

3.5. ( , 1.8 - 1, , .) . , .

3.6. ( ; - -?). () , ; () , (RVA-).

3.7. () RVA- -, () RVA-. -, , RVA-. RVA- - , , , RVA-.

3.8. TABLE_DUM and TABLE_DEE. SQL?

3.9. TABLE_DEE TRUE, TABLE_DUM FALSE. , BOOLEAN? , DEE DUM , - . , -- 0?

3.10. ( - ) SQL:

VALUES ( 1, 2 ), ( 2, 1 ), ( 1, 1 ), ( 1, 2 )

VALUES ( ( 1, 2 ), ( 2, 1 ), ( 1, 1 ), ( 1, 2 ) )

100 3. ,

3.11. SQL?

SELECT SNO FROM S WHERE ( NOT ( ( STATUS , SNO )

4. , null-

():

-, (), - .

null-, - , null-.

, , , - . . : -, SQL, , , SQL, ( , -). , , .

? , - ( ) . , .1 , , :

1 , - ( , ) , , , , 1 . .

102 4. , null-

1. , , , ( -).

2. , , . - - exp1 (, , ) - exp2 , - , exp2 ( , ). : , - - .

. , , , -, , SQL - - , -. () , . 4.1. , ( ). : , , , , , -

PNO PNAMEP

P1 ScrewP1 ScrewP1 ScrewP2 Screw

SNO PNOSP

S1 P1S1 P1S1 P2

. 4.1.

, : - P (P1,Screw), , , , ? - , ? - :

, -. , - - , , - . , , , Double Trouble, Double Trouble (. D).

? 103

, -, 1.

, - - , . ( , - , - , , , . , - .) - , , - , , P - (P1,Screw), , , - - -. , () ?

: , - (screw), S1, . SQL :

1. SELECT P.PNO FROM P WHERE P.PNAME = Screw OR P.PNO IN ( SELECT SP.PNO FROM SP WHERE SP.SNO = S1 )

: P1 * 3, P2 * 1.

2. SELECT SP.PNO FROM SP WHERE SP.SNO = S1 OR SP.PNO IN ( SELECT P.PNO FROM P WHERE P.PNAME = Screw )

: P1 * 2, P2 * 1.

3. SELECT P.PNO FROM P, SP WHERE ( SP.SNO = S1 AND SP.PNO = P.PNO ) OR P.PNAME = Screw

1 - , - : !, : , .

104 4. , null-

: P1 * 9, P2 * 4.

4. SELECT SP.PNO FROM P, SP WHERE ( SP.SNO = S1 AND SP.PNO = P.PNO ) OR P.PNAME = Screw

: P1 * 8, P2 * 4.

5. SELECT P.PNO FROM P WHERE P.PNAME = Screw UNION ALL SELECT SP.PNO FROM SP WHERE SP.SNO = S1

: P1 * 5, P2 * 2.

6. SELECT DISTINCT P.PNO FROM P WHERE P.PNAME = Screw UNION ALL SELECT SP.PNO FROM SP WHERE SP.SNO = S1

: P1 * 3, P2 * 2.

7. SELECT P.PNO FROM P WHERE P.PNAME = Screw UNION ALL SELECT DISTINCT SP.PNO FROM SP WHERE SP.SNO = S1

: P1 * 4, P2 * 2.

8. SELECT P.PNO FROM P WHERE P.PNAME = Screw OR P.PNO IN ( SELECT SP.PNO FROM SP WHERE SP.SNO = S1 )

: P1 * 3, P2 * 1.

9. SELECT DISTINCT SP.PNO FROM SP WHERE SP.SNO = S1 OR SP.PNO IN ( SELECT P.PNO

? 105

FROM P WHERE P.PNAME = Screw )

: P1 * 1, P2 * 1.

10. SELECT P.PNO FROM P GROUP BY P.PNO, P.PNAME HAVING P.PNAME = Screw OR P.PNO IN ( SELECT SP.PNO FROM SP WHERE SP.SNO = S1 )

: P1 * 1, P2 * 1.

11. SELECT P.PNO FROM P, SP GROUP BY P.PNO, P.PNAME, SP.SNO, SP.PNO HAVING ( SP.SNO = S1 AND SP.PNO = P.PNO ) OR P.PNAME = Screw

: P1 * 2, P2 * 2.

12. SELECT P.PNO FROM P WHERE P.PNAME = Screw UNION SELECT SP.PNO FROM SP WHERE SP.SNO = S1

: P1 * 1, P2 * 1.

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VAR S BASE RELATION | CREATE TABLE S { SNO CHAR , | ( SNO VARCHAR(5) NOT NULL , SNAME CHAR , | SNAME VARCHAR(25) NOT NULL , STATUS INTEGER , | STATUS INTEGER NOT NULL , CITY CHAR } | CITY VARCHAR(20) NOT NULL , KEY { SNO } ; | UNIQUE ( SNO ) ) ;

VAR P BASE RELATION | CREATE TABLE P { PNO CHAR , | ( PNO VARCHAR(6) NOT NULL , PNAME CHAR | PNAME VARCHAR(25) NOT NULL , COLOR CHAR , | COLOR CHAR(10) NOT NULL , WEIGHT FIXED , | WEIGHT NUMERIC(5,1) NOT NULL , CITY CHAR } | CITY VARCHAR(20) NOT NULL , KEY { PNO } ; | UNIQUE ( PNO ) ) ;

VAR SP BASE RELATION | CREATE TABLE SP { SNO CHAR , | ( SNO VARCHAR(5) NOT NULL , PNO CHAR , | PNO VARCHAR(6) NOT NULL , QTY INTEGER } | QTY INTEGER NOT NULL , KEY { SNO , PNO } | UNIQUE ( SNO , PNO ) , FOREIGN KEY { SNO } | FOREIGN KEY ( SNO ) REFERENCES S | REFERENCES S ( SNO ) , FOREIGN KEY { PNO } | FOREIGN KEY ( PNO ) REFERENCES P ; | REFERENCES P ( PNO ) ) ;

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UPDATE S | UPDATE S WHERE SNO = S1 | SET CITY = New York OR SNO = S4 : | WHERE SNO = S1 { CITY := New York } ; | OR SNO = S4 ;

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UPDATE S WHERE SNO = S5 : | UPDATE S { CITY := New York } ; | SET CITY = New York | WHERE SNO = S5 ;

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S := S WHERE NOT ( CITY = Athens ) ;

1 , DELETE Tutorial D:

DELETE S WHERE CITY = Athens ;

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DELETE R WHERE bx ;

( R - , bx ) :

R := R WHERE NOT ( bx ) ;

INSERT Tutorial D

INSERT R rx ;

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R := R D_UNION rx ;

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