sql 如果您需要将数据从一个SQL Server数据库（或表）迁移到另一个不同的列大小的位置

Posted 2021-05-13

--Truncate and Trim the Data to fit new Column
--NOTE: Before doing this you should run the above script to see if you need to increase Column Size
SELECT RTRIM(LTRIM(LEFT(FirstName, 50))) AS [FirstName]
FROM   OldDatabase.dbo.OldTable;

--Source Discussion: https://community.spiceworks.com/topic/131997-sql-copy-field-in-to-smaller-field
--Author: Jason Crider - https://twitter.com/jasoncrider

--Get MaxLength on all columns in a table
DECLARE @SQL VARCHAR(MAX)

DECLARE @TableName sysname

SET @TableName = 'INSERT_TABLENAME_HERE'

SET @SQL = ''

SELECT @SQL = @SQL + 'SELECT ' + QUOTENAME(sc.name, '''') + ' AS ColumnName, ' + QUOTENAME(t.name, '''') + ' AS DataType, ' +

QUOTENAME(sc.max_length, '''') + ' AS SetLength, MAX(DATALENGTH(' + QUOTENAME(sc.name) + ')) AS MaxLength FROM '+@TableName+ char(10) +' UNION '

FROM sys.columns sc

join sys.types t on t.system_type_id = sc.system_type_id and t.name != 'sysname'

WHERE sc.OBJECT_ID = OBJECT_ID(@TableName)

SET @SQL = LEFT(@SQL, LEN(@SQL)-6)

PRINT @SQL

EXEC(@SQL)