获取列、varchar或nvarchar的实际长度/避免截断错误[duplicate]

select column_name, data_type, character_maximum_length    
  from information_schema.columns  
 where table_name = 'myTable'

特别是在SQL Server上:

SELECT DATALENGTH(Remarks) AS FIELDSIZE FROM mytable

Documentation

对于SQL Server(2008及更高版本):

SELECT COLUMNPROPERTY(OBJECT_ID('mytable'), 'Remarks', 'PRECISION');

COLUMNPROPERTY返回列或参数(id,column/parameter,property)的信息。PRECISION属性返回列或参数的数据类型的长度。

COLUMNPROPERTY documentation

这将在SQL SERVER上工作。。。

SELECT COL_LENGTH('Table', 'Column')

我在寻找专栏的总大小,然后点击这篇文章,我的解决方案是基于MarcE的。

SELECT sum(DATALENGTH(your_field)) AS FIELDSIZE FROM your_table

SELECT
    s.name
    , o.name as table_name
    , c.name as column_name
    , t.name as type
    , c.max_length
    , c.collation_name
    , c.is_nullable
FROM
    sys.columns c
    INNER JOIN sys.objects o ON (o.object_id = c.object_id)
    INNER JOIN sys.schemas s ON (s.schema_id = o.schema_id)
    INNER JOIN sys.types t ON (t.user_type_id = c.user_type_id)
WHERE
    s.name = 'dbo'
    AND t.name IN ('varchar') -- , 'char', 'nvarchar', 'nchar')
ORDER BY
    o.name, c.name

select column_name, data_type, character_maximum_length    
from INFORMATION_SCHEMA.COLUMNS
where table_name = 'Table1'

此函数用于计算varchar(Nn)的最大有效长度:

CREATE FUNCTION [dbo].[GetMaxVarcharColumnLength] (@TableSchema NVARCHAR(MAX), @TableName NVARCHAR(MAX), @ColumnName VARCHAR(MAX))
RETURNS INT
AS
BEGIN
    RETURN (SELECT character_maximum_length FROM information_schema.columns  
            WHERE table_schema = @TableSchema AND table_name = @TableName AND column_name = @ColumnName);
END

用法:

IF LEN(@Name) > [dbo].[GetMaxVarcharColumnLength]('person', 'FamilyStateName', 'Name') 
            RETURN [dbo].[err_Internal_StringForVarcharTooLong]();