当表的列放置约束[主要是长度]时，抛出此错误。例如，如果列myColumn的数据库模式是CHAR(2)，那么当你从任何应用程序调用插入值时，你必须传递长度为2的字符串。

误差基本上说明了这一点;长度为3及以上的字符串不符合数据库模式指定的长度限制。这就是为什么SQL Server警告并抛出数据丢失/截断错误。

我构建了一个存储过程，它分析一个源表或查询，每个列都有几个特征，其中最小长度(min_len)和最大长度(max_len)。

CREATE PROCEDURE [dbo].[sp_analysetable] (
  @tableName varchar(8000),
  @deep bit = 0
) AS

/*
sp_analysetable 'company'
sp_analysetable 'select * from company where name is not null'
*/

DECLARE @intErrorCode INT, @errorMSG VARCHAR(500), @tmpQ NVARCHAR(2000), @column_name VARCHAR(50), @isQuery bit
SET @intErrorCode=0

IF OBJECT_ID('tempdb..##tmpTableToAnalyse') IS NOT NULL BEGIN
  DROP TABLE ##tmpTableToAnalyse
END
IF OBJECT_ID('tempdb..##tmpColumns') IS NOT NULL BEGIN
  DROP TABLE ##tmpColumns
END

if CHARINDEX('from', @tableName)>0
  set @isQuery=1

IF @intErrorCode=0 BEGIN
  if @isQuery=1 begin
    --set @tableName = 'USE '+@db+';'+replace(@tableName, 'from', 'into ##tmpTableToAnalyse from')
    --replace only first occurance. Now multiple froms may exists, but first from will be replaced with into .. from
    set @tableName=Stuff(@tableName, CharIndex('from', @tableName), Len('from'), 'into ##tmpTableToAnalyse from')
    exec(@tableName)
    IF OBJECT_ID('tempdb..##tmpTableToAnalyse') IS NULL BEGIN
      set @intErrorCode=1
      SET @errorMSG='Error generating temporary table from query.'
    end
    else begin
      set @tableName='##tmpTableToAnalyse'
    end
  end
end

IF @intErrorCode=0 BEGIN
  SET @tmpQ='USE '+DB_NAME()+';'+CHAR(13)+CHAR(10)+'
  select
    c.column_name as [column],
    cast(sp.value as varchar(1000)) as description,
    tc_fk.constraint_type,
    kcu_pk.table_name as fk_table,
    kcu_pk.column_name as fk_column,
    c.ordinal_position as pos,
    c.column_default as [default],
    c.is_nullable as [null],
    c.data_type,
    c.character_maximum_length as length,
    c.numeric_precision as [precision],
    c.numeric_precision_radix as radix,
    cast(null as bit) as [is_unique],
    cast(null as int) as min_len,
    cast(null as int) as max_len,
    cast(null as int) as nulls,
    cast(null as int) as blanks,
    cast(null as int) as numerics,
    cast(null as int) as distincts,
    cast(null as varchar(500)) as distinct_values,
    cast(null as varchar(50)) as remarks
  into ##tmpColumns'
  if @isQuery=1 begin
    SET @tmpQ=@tmpQ+' from tempdb.information_schema.columns c, (select null as value) sp'
  end
  else begin
    SET @tmpQ=@tmpQ+'
      from information_schema.columns c
      left join sysobjects so    on so.name=c.table_name  and so.xtype=''U''
      left join syscolumns sc    on sc.name=c.column_name and sc.id  =so.id 
      left join sys.extended_properties sp on sp.minor_id = sc.colid AND sp.major_id = sc.id and sp.name=''MS_Description''  
      left join information_schema.key_column_usage kcu_fk    on kcu_fk.table_name = c.table_name     and c.column_name = kcu_fk.column_name
      left join information_schema.table_constraints tc_fk    on kcu_fk.table_name = tc_fk.table_name and kcu_fk.constraint_name = tc_fk.constraint_name
      left join information_schema.referential_constraints rc on rc.constraint_name = kcu_fk.constraint_name
      left join information_schema.table_constraints tc_pk    on rc.unique_constraint_name = tc_pk.constraint_name
      left join information_schema.key_column_usage kcu_pk    on tc_pk.constraint_name = kcu_pk.constraint_name
 '
  end
  SET @tmpQ=@tmpQ+' where c.table_name = '''+@tableName+''''

  exec(@tmpQ)
end

IF @intErrorCode=0 AND @deep = 1 BEGIN
  DECLARE
    @count_rows int,
    @count_distinct int,
    @count_nulls int,
    @count_blanks int,
    @count_numerics int,
    @min_len int,
    @max_len int,
    @distinct_values varchar(500)
  DECLARE curTmp CURSOR LOCAL FAST_FORWARD FOR
    select [column] from ##tmpColumns;
  OPEN curTmp
  FETCH NEXT FROM curTmp INTO @column_name
  WHILE @@FETCH_STATUS = 0 and @intErrorCode=0 BEGIN
    set @tmpQ = 'USE '+DB_NAME()+'; SELECT'+
      '  @count_rows=count(0), '+char(13)+char(10)+
      '  @count_distinct=count(distinct ['+@column_name+']),'+char(13)+char(10)+
      '  @count_nulls=sum(case when ['+@column_name+'] is null then 1 else 0 end),'+char(13)+char(10)+
      '  @count_blanks=sum(case when ltrim(['+@column_name+'])='''' then 1 else 0 end),'+char(13)+char(10)+
      '  @count_numerics=sum(isnumeric(['+@column_name+'])),'+char(13)+char(10)+
      '  @min_len=min(len(['+@column_name+'])),'+char(13)+char(10)+
      '  @max_len=max(len(['+@column_name+']))'+char(13)+char(10)+
      ' from ['+@tableName+']'
    exec sp_executesql @tmpQ,
                       N'@count_rows int OUTPUT,
                         @count_distinct int OUTPUT,
                         @count_nulls int OUTPUT,
                         @count_blanks int OUTPUT,
                         @count_numerics int OUTPUT,
                         @min_len int OUTPUT,
                         @max_len int OUTPUT',
                       @count_rows     OUTPUT,
                       @count_distinct OUTPUT,
                       @count_nulls    OUTPUT,
                       @count_blanks    OUTPUT,
                       @count_numerics OUTPUT,
                       @min_len        OUTPUT,
                       @max_len        OUTPUT

    IF (@count_distinct>10) BEGIN
      SET @distinct_values='Many ('+cast(@count_distinct as varchar)+')'
    END ELSE BEGIN
      set @distinct_values=null
      set @tmpQ = N'USE '+DB_NAME()+';'+
        '  select @distinct_values=COALESCE(@distinct_values+'',''+cast(['+@column_name+'] as varchar),  cast(['+@column_name+'] as varchar))'+char(13)+char(10)+
        '  from ('+char(13)+char(10)+
        '    select distinct ['+@column_name+'] from ['+@tableName+'] where ['+@column_name+'] is not null) a'+char(13)+char(10)
      exec sp_executesql @tmpQ,
                         N'@distinct_values varchar(500) OUTPUT',
                         @distinct_values        OUTPUT
    END
    UPDATE ##tmpColumns SET
      is_unique      =case when @count_rows=@count_distinct then 1 else 0 end,
      distincts      =@count_distinct,
      nulls          =@count_nulls,
      blanks         =@count_blanks,
      numerics       =@count_numerics,
      min_len        =@min_len,
      max_len        =@max_len,
      distinct_values=@distinct_values,
      remarks       =
        case when @count_rows=@count_nulls then 'all null,' else '' end+
        case when @count_rows=@count_distinct then 'unique,' else '' end+
        case when @count_distinct=0 then 'empty,' else '' end+
        case when @min_len=@max_len then 'same length,' else '' end+
        case when @count_rows=@count_numerics then 'all numeric,' else '' end
    WHERE [column]=@column_name

    FETCH NEXT FROM curTmp INTO @column_name
  END
  CLOSE curTmp DEALLOCATE curTmp
END

IF @intErrorCode=0 BEGIN
  select * from ##tmpColumns order by pos
end

IF @intErrorCode=0 BEGIN --Clean up temporary tables
  IF OBJECT_ID('tempdb..##tmpTableToAnalyse') IS NOT NULL BEGIN
    DROP TABLE ##tmpTableToAnalyse
  END
  IF OBJECT_ID('tempdb..##tmpColumns') IS NOT NULL BEGIN
    DROP TABLE ##tmpColumns
  END
end

IF @intErrorCode<>0 BEGIN
  RAISERROR(@errorMSG, 12, 1)
END
RETURN @intErrorCode

我把这个过程存储在主数据库中，这样我就可以在每个数据库中使用它，就像这样:

sp_analysetable 'table_name', 1
// deep=1 for doing value analyses

输出为:

column description constraint_type fk_table fk_column pos default null data_type length precision radix is_unique min_len max_len nulls blanks numerics distincts distinct_values remarks id_individual NULL PRIMARY KEY NULL NULL 1 NULL NO int NULL 10 10 1 1 2 0 0 70 70 Many (70) unique,all numeric, id_brand NULL NULL NULL NULL 2 NULL NO int NULL 10 10 0 1 1 0 0 70 2 2,3 same length,all numeric, guid NULL NULL NULL NULL 3 (newid()) NO uniqueidentifier NULL NULL NULL 1 36 36 0 0 0 70 Many (70) unique,same length, customer_id NULL NULL NULL NULL 4 NULL YES varchar 50 NULL NULL 0 NULL NULL 70 0 0 0 NULL all null,empty, email NULL NULL NULL NULL 5 NULL YES varchar 100 NULL NULL 0 4 36 0 0 0 31 Many (31) mobile NULL NULL NULL NULL 6 NULL YES varchar 50 NULL NULL 0 NULL NULL 70 0 0 0 NULL all null,empty, initials NULL NULL NULL NULL 7 NULL YES varchar 50 NULL NULL 0 NULL NULL 70 0 0 0 NULL all null,empty, title_short NULL NULL NULL NULL 8 NULL YES varchar 50 NULL NULL 0 NULL NULL 70 0 0 0 NULL all null,empty, title_long NULL NULL NULL NULL 9 NULL YES varchar 50 NULL NULL 0 NULL NULL 70 0 0 0 NULL all null,empty, firstname NULL NULL NULL NULL 10 NULL YES varchar 50 NULL NULL 0 NULL NULL 70 0 0 0 NULL all null,empty, lastname NULL NULL NULL NULL 11 NULL YES varchar 50 NULL NULL 0 NULL NULL 70 0 0 0 NULL all null,empty, address NULL NULL NULL NULL 12 NULL YES varchar 100 NULL NULL 0 NULL NULL 70 0 0 0 NULL all null,empty, pc NULL NULL NULL NULL 13 NULL YES varchar 10 NULL NULL 0 NULL NULL 70 0 0 0 NULL all null,empty, kixcode NULL NULL NULL NULL 14 NULL YES varchar 20 NULL NULL 0 NULL NULL 70 0 0 0 NULL all null,empty, date_created NULL NULL NULL NULL 15 (getdate()) NO datetime NULL NULL NULL 1 19 19 0 0 0 70 Many (70) unique,same length, created_by NULL NULL NULL NULL 16 (user_name()) NO varchar 50 NULL NULL 0 13 13 0 0 0 1 loyalz-public same length, id_location_created NULL FOREIGN KEY location id_location 17 NULL YES int NULL 10 10 0 1 1 0 0 70 2 1,2 same length,all numeric, id_individual_type NULL FOREIGN KEY individual_type id_individual_type 18 NULL YES int NULL 10 10 0 NULL NULL 70 0 0 0 NULL all null,empty, optin NULL NULL NULL NULL 19 NULL YES int NULL 10 10 0 1 1 39 0 31 2 0,1 same length,

当表的列放置约束[主要是长度]时，抛出此错误。例如，如果列myColumn的数据库模式是CHAR(2)，那么当你从任何应用程序调用插入值时，你必须传递长度为2的字符串。

误差基本上说明了这一点;长度为3及以上的字符串不符合数据库模式指定的长度限制。这就是为什么SQL Server警告并抛出数据丢失/截断错误。

这里有一个稍微不同的答案。您的列名和长度可能都匹配，但可能您在SELECT语句中以错误的顺序指定了列。假设tableX和tableY的列名称相同，但顺序不同

您需要发布源表和目标表的表定义，以便我们找出问题所在，但底线是源表中的一列比目标列大。这可能是您正在以一种您没有意识到的方式更改格式。要弄清楚这一点，您要使用的数据库模型也很重要。

请尝试以下代码:

CREATE TABLE [dbo].[Department](
    [Department_name] char(10) NULL
)

INSERT INTO [dbo].[Department]([Department_name]) VALUES  ('Family Medicine')
--error will occur

 ALTER TABLE [Department] ALTER COLUMN [Department_name] char(50)

INSERT INTO [dbo].[Department]([Department_name]) VALUES  ('Family Medicine')

select * from [Department]