SQL Server/T-SQL/Constraints/Constraints Basics — различия между версиями
Admin (обсуждение | вклад) м (1 версия) |
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(нет различий)
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Текущая версия на 13:21, 26 мая 2010
Enable a column to optionally not require a value by designating it as a nullable column
<source lang="sql">
1> -- Nullability 2> 3> -- Enable a column to optionally not require a value by designating it as a 4> -- nullable column. 5> 6> CREATE TABLE MyTable 7> ( Category nVarChar(50) NOT NULL 8> , MyDescription nVarChar(50) 9> ) 10> INSERT MyTable (Category) VALUES ("Category1") 11> 12> SELECT * FROM MyTable 13> GO (1 rows affected) Category MyDescription
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Category1 NULL (1 rows affected) 1> 2> drop table MyTable 3> GO 1>
</source>
NOT NULL column and NULL column
<source lang="sql">
1> CREATE TABLE MyTable 2> ( Category nVarChar(50) NOT NULL 3> , MyDescription nVarChar(50) NULL 4> ) 5> 6> 7> INSERT MyTable (Category) VALUES ("Category1") 8> 9> SELECT * FROM MyTable 10> GO (1 rows affected) Category MyDescription
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Category1 NULL (1 rows affected) 1> 2> drop table MyTable 3> GO 1>
</source>