Question

我有这个更新触发器，但它会记录列，即使新旧值是相同的值。（这是因为EntityFramework更新语句的方式）。

set nocount on;
    create table #updatedCols (Id int identity(1, 1), updateCol nvarchar(200))

    --find all columns that were updated and write them to temp table
    insert into #updatedCols (updateCol)
    select
        column_name
    from
        information_schema.columns
    where   
        table_name = 'Items'   
        and convert(varbinary, reverse(columns_updated())) & power(convert(bigint, 2), ordinal_position - 1) > 0

    --temp tables are used because inserted and deleted tables are not available in dynamic SQL
    select * into #tempInserted from inserted
    select * into #tempDeleted from deleted

    declare @cnt int = 1
    declare @rowCnt int
    declare @columnName varchar(1000)
    declare @sql nvarchar(4000)

    select @rowCnt = count(*) from #updatedCols

    --execute insert statement for each updated column
    while @cnt <= @rowCnt
    begin
        select @columnName = updateCol from #updatedCols where id = @cnt

        set @sql = N'
            insert into [Events] ([RecordId], [EventTypeId], [EventDate], [ColumnName], [OriginalValue], [NewValue], [TenantId], [AppUserId], [TableName])
            select
                i.Id, 2, GetUTCDate(), ''' + @columnName + ''', d.' + @columnName + ', i.' + @columnName +', i.TenantId, i.UpdatedBy, ''Item''
            from
                #tempInserted i
                join #tempDeleted d on i.Id = d.Id

            '
        exec sp_executesql @sql
        set @cnt = @cnt + 1
    end

所以我添加了更新连接以过滤掉值相同的位置：

 #tempDeleted d on i.Id = d.Id and isnull(i.' + @columnName + ', '''') <> isnull(d.' +@columnName + ', '''')

但是，我现在收到错误：SqlException: Error converting data type varchar to numeric.

我猜测在某些情况下旧值为null（因此转换为空字符串），新值为int，因此Sql Server尝试将varchar转换为int以便比较它们并抛出错误。

这是对的吗？如果是这样，我该如何解决？

Answer 1

如果您不想参数化变量，请执行以下操作

isnull(i.' + convert(varchar(100),@columnName) + ', '''')

否则使用参数定义选项

https://docs.microsoft.com/en-us/sql/relational-databases/system-stored-procedures/sp-executesql-transact-sql?view=sql-server-2017

为什么我在使用isNull时收到此错误消息

1 个答案: