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FAQ

SQL

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SQL :

>::=CREATE TABLE < >( > [{,< >}])< >::=< > > >::=< > < >[< >][< >]< >::=DEFAULT { <literal> | USER | NULL } >::=NOT NULL[ >] >CHECK (< >) >::= UNIQUE< >::=FOREIGN KEY < > < >::= REFERENCES < > (< >)

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CREATE TABLE , .

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  • 5 1000.
CREATE TABLE BOOKS (ISBN varchar(14) NOT NULL PRIMARY KEY, TITLE varchar(120) NOT NULL, AUTOR varchar(30) NULL, COAUTOR varchar(30) NULL, YEAR_PUBL smallint DEFAULT Year(GetDate()) CHECK(YEAR_PUBL >= 1960 AND YEAR_PUBL <= YEAR(GetDate())), PUBLICH varchar(20) NULL, PAGES smallint CHECK(PAGES > = 5 AND PAGES <= 1000));

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ALTER TABLE:

< >::= ALTER TABLE < > { ADD > ALTER < > {SET DEFAULT <> DROP DEFAULT } | DROP < > {CASCADE | RESTRICT} | ADD { < >| < > | < > | < > } | DROP CONSTRAINT { CASCADE | RESTRICT} }

ALTER TABLE , , . , .

. . ALTER TABLE , . EDUCATION (), , ("", "", " ", "") READERS.

ALTER TABLE READERSADD EDUCATION varchar (30) DEFAULT NULLCHECK (EDUCATION IS NULL OR EDUCATION= "" OR EDUCATION= " " OR EDUCATION= " " OR EDUCATION= "")

READERS EDUCATION, . .

SQL

SELECT

(Data Query Language) SQL SELECT. . , . SQL ( ) . , . , , , , , , .

SELECT :

SELECT[ALL|DISTINCT](< >|*)FROM < >[WHERE <- >][GROUP BY < >][HAVING <- >][ORDER BY < , >]

ALL , , . , . ( , ). DISTINCT , , .

*. () , .

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WHERE , .

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ORDER BY , , . , , , , , .

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< >IS NULL < > IS NOT NULL.

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SELECT .

SELECT . ,

SELECT * FROM R1, R2

R1 R2.

SELECT R1.A, R2.B FROM R1, R2

A R1 B R2, , , .

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, . R1, R2, R3. , R1, R2 R3 .

R1 = (, , ); R2 = (, ); R3 = (, )

R1
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R2
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R3
 
 
 
 
 

on_load_lecture();

SELECT.

SELECT DISTINCT FROM R3

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SELECT η FROM R1 WHERE = " " AND = 5

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SELECT , FROM R2,R3 WHERE R2. = R3.;

WHERE R2 R3, WHERE , R3, , .

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SELECT DISTINCT R1.η FROM R1 a, R1 b WHERE a. = b. AND a. <> b. AND a. <= 2 AND b. <= 2;

R1 a b, .

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: 2016-07-29; !; : 2060 |

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