(query) . , , . : (QBE by example) (SQL Structured Language).
SQL , () SQL . , . Access SQL , , /SQL.
. SQL : DDL (Data Definition Language - ) DML (Data Manipulation Language - ). DDL , , DML - , , , , .
.
CREATE DATABASE _
USE _
Query Analyzer, master.
CREATE TABLE. ( ):
CREATE TABLE _(
__,
[__]);
:
_ _[()]
[NULL] [NOT NULL]
[PRIMARY KEY]
[UNIQUE]
[IDENTITY]
[DEFAULT ]
[CHECK ()]
[REFERENCES _(_)]
:
VARCHAR - ;
NUMERIC - ;
DATETIME - /.
NULL - "" , SQL. NULL/NOT NULL , / NULL-.
PRIMARY KEY - , , ( !) p .
UNIQUE - , , . .
IDENTITY _, - , , , ., . "_" "" , 1.
DEFAULT - , , .., , , .
CHECK ()- , .
REFERENCES _(_) - .
, , .
. CONSTRAINT . CHECK .
:
CONSTRAINT _ FOREIGN KEY (_)
REFERENCES _( )
, , :
CONSTRAINT _ PRIMARY KEY (_)
, SQL-, . - , . , , GO.
