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1.5.1. " ". CHARACTER AR . ;
RR[(<>)]
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: , CHAR, , <>. 1 255, ., 255 . ; <>, . , <> . - .
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, CHARACTER VARCHAR, SQL ; , '<>'
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1.5.2. . SQL :
INTEGER - - : - -231 +231,
SMALLINT - , INTEGER, -215 +215;
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NUMERIC(<>[, < >]) , , , DECIMAL
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DOUBLE PRECISION - -, - REAL, REAL.
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1.5.3. . SQL. . Oracle DATE . . : DATE -, .
DATE : , . , '03.05.1999' '12/06/1989', '03-nov-1999', '03-apr-99'.
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1.5.4. (NULL). , SQL NULL. " NULL ". , NULL , . , - . , NULL.
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(NULL), ( " NULL").
IS NULL IS NOT NULL ( "=" ).
, NULL , (NULL).