blocks|key|1394020|text|使用Alter+table语句。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1394021|Alter+table+TableName+Alter+Column+ColumnName+nvarchar(100)|code-block|syntax|javascript|1394022|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Use the Alter table statement.

<pre><code>Alter table TableName Alter Column ColumnName nvarchar(100)
</code></pre>

blocks|key|1608962|text|别忘了可空性。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1608963|ALTER+TABLE+<schemaName>.<tableName>
ALTER+COLUMN+<columnName>+nvarchar(200)+[NULL%7CNOT+NULL]|code-block|syntax|javascript|1608964|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Don't forget nullability.

<pre><code>ALTER TABLE &lt;schemaName&gt;.&lt;tableName&gt;
ALTER COLUMN &lt;columnName&gt; nvarchar(200) [NULL|NOT NULL]
</code></pre>

blocks|key|1394046|text|试试这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1394047|ALTER+TABLE+"table_name"
MODIFY+"column_name"+"New+Data+Type";|code-block|syntax|javascript|1394048|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Try this:

<pre><code>ALTER TABLE "table_name"
MODIFY "column_name" "New Data Type";
</code></pre>

blocks|key|1394106|text|在SQL+Server+(Transact-SQL)中修改现有表中的列的语法为：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1394107|ALTER+TABLE+table_name
++++ALTER+COLUMN+column_name+column_type;|code-block|syntax|javascript|1394108|例如：|1394109|ALTER+TABLE+employees
++++ALTER+COLUMN+last_name+VARCHAR(75)+NOT+NULL;|1394110|此SQL+Server+ALTER+TABLE示例将把名为last_name的列修改为VARCHAR(75)的数据类型，并强制该列不允许使用空值。|offset|length|style|CODE|1394111|请参阅here|1394112|entityMap|0|LINK|mutability|MUTABLE|url|http://www.techonthenet.com/sql_server/tables/alter_table.php^0|0|0|0|0|C|B|T|9|17|B|0|3|4|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|12|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|14|8|@$M|15|N|16|O|P]|$M|17|N|18|O|P]|$M|19|N|1A|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1B|8|@]|9|@$M|1C|N|1D|1|1E]]|A|$]]|$1|S|3|-4|5|6|7|1F|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]]]

The syntax to modify a column in an existing table in SQL Server (Transact-SQL) is:



<pre class="lang-sql prettyprint-override"><code>ALTER TABLE table_name
 ALTER COLUMN column_name column_type;
</code></pre>

For example:

<pre class="lang-sql prettyprint-override"><code>ALTER TABLE employees
 ALTER COLUMN last_name VARCHAR(75) NOT NULL;
</code></pre>

This SQL Server <code>ALTER TABLE</code> example will modify the column called <code>last_name</code> to be a data type of <code>VARCHAR(75)</code> and force the column to not allow null values.

see <a href="http://www.techonthenet.com/sql_server/tables/alter_table.php" rel="noreferrer">here</a>

blocks|key|1609054|text|ALTER+TABLE+[dbo].[TableName]
ALTER+COLUMN+ColumnName+VARCHAR(Max)+NULL|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1609055|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>ALTER TABLE [dbo].[TableName]
ALTER COLUMN ColumnName VARCHAR(Max) NULL
</code></pre>

blocks|key|1394150|text|在11g中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1394151|ALTER+TABLE+TableName
Modify+ColumnName+DataType;|code-block|syntax|javascript|1394152|例如:+ALTER+TABLE+employees+BIRTH_DATE+VARCHAR30；|1394153|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

in 11g:
<pre><code>ALTER TABLE TableName
Modify ColumnName DataType;
</code></pre>
EG:
ALTER TABLE employees
Modify BIRTH_DATE VARCHAR(30);

blocks|key|1394157|text|ALTER+TABLE+[Performance].[dbo].[CRA_283_Violation]
ALTER+COLUMN+[Throughput_HS_DC_NodeB_3G_Alarm]+bit|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1394158|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>ALTER TABLE [Performance].[dbo].[CRA_283_Violation]
ALTER COLUMN [Throughput_HS_DC_NodeB_3G_Alarm] bit
</code></pre>

I am trying to change a column from a <code>varchar(50)</code> to a <code>nvarchar(200)</code>. What is the SQL command to alter this table?

How do you change the datatype of a column in SQL Server?

SQL Server

我正在尝试将列从varchar(50)更改为nvarchar(200)。更改此表的SQL命令是什么？

问如何在SQL Server中更改列的数据类型？
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