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UPDATE




UPDATE , DELETE . DELETE , . , , , :

UPDATE Salespeople
SET comm = comm +.01
WHERE 2 <= (SELECT COUNT (cnum)
FROM Customers
WHERE Customers.snum = Salespeople.snum);

Peel Serres, , .

DELETE. , , :

UPDATE salespeople
SET comm = comm -.01
WHERE snum IN (SELECT snum
FROM Orders a
WHERE amt = (SELECT MIN (amt)
FROM Orders b
WHERE a.odate = b.odate));

DML

, (UPDATE), .

, , . , ( 1.), , , ( 2.), :

1.

SELECT AVG (rating)
FROM Customers;

= 200.

2.

DELETE
FROM Customers
WHERE rating < 200;

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18.

CREATE TABLE. . DML INSERT (. 15). CREATE TABLE , . . , , .

CREATE TABLE:

CREATE TABLE <table-name >
(<column name > <data type>[(<size>)],
<column name > <data type> [(<size>)]...);

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:

CREATE TABLE Saleepeople
(snum integer,
sname char (10),
city char (10),
comm declmal);

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, . , , cnum=2999. , , , cnum 2999. cnum, 2999 , .

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(, ANSI ):

CREATE INDEX <index name> ON <table name>
(<column name> [,<column name>]...);

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, , , snum .

CREATE INDEX Clientgroup ON Customers (snum);

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, , , , . . , , UNIQUE INDEX. num, , :

CREATE UNIQUE INDEX Custid ON Customers (cnum);

: , cnum. , , , . , , , , .

cnum . . 18 19.

, . . SQL , , , . , , . :

DROP INDEX <Index name>;

.





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