Question

我有这种方法可以在另一个数据库的表中添加与另一个数据库相同的值：

public function insert()
{
    $indexes= DB::connection('sqlsrv')
            ->select
            (
            "
            IF  NOT EXISTS (SELECT * FROM sys.objects 
            WHERE object_id = OBJECT_ID(N'[test].[dbo].[indexes]') AND type in (N'U'))
            CREATE TABLE test.dbo.indexes 
                (
                    table_view nvarchar(500) not null,
                    [columns] nvarchar(500) not null,
                    [type] nvarchar(50) not null,
                    index_name nvarchar(500) not null,
                    index_id int not null
                )
            insert into test.dbo.indexes (table_view, [columns], [type], index_name, index_id)

            select 
            schema_name(t.schema_id) + '.' + t.[name] as table_view,
            substring(column_names, 1, len(column_names)-1) as [columns],
            case when i.is_primary_key = 1 then 'Primary_key'
            when i.is_unique = 1 then 'Unique'
            else 'Not_unique' end as [type],
            i.[name] as index_mane,
            i.index_id
            from sys.objects t
            inner join sys.indexes i
            on t.object_id = i.object_id
            cross apply (select col.[name] + ', '
                from sys.index_columns ic
                    inner join sys.columns col
                        on ic.object_id = col.object_id
                        and ic.column_id = col.column_id
                where ic.object_id = t.object_id
                    and ic.index_id = i.index_id
                        order by col.column_id
                        for xml path ('') ) D (column_names)
            where t.is_ms_shipped <> 1
            and index_id > 0
            order by schema_name(t.schema_id) + '.' + t.[name], i.index_id
            "
            );
}

问题是，当我多次运行此记录时，记录被重复了。我该怎么做才能阻止这种情况？我需要这样，当我第二次，第三次，X次运行此命令时，仅添加不相同的内容。

Answer 1

使用not exists条件测试重复项，如下所示。

insert into test.dbo.indexes (table_view, [columns], [type], index_name, index_id)
select table_view, [columns], [type], index_name, index_id
from (
    select 
        schema_name(t.[schema_id]) + '.' + t.[name] as table_view
        , substring(column_names, 1, len(column_names)-1) as [columns]
        , case when i.is_primary_key = 1 then 'Primary_key'
            when i.is_unique = 1 then 'Unique'
            else 'Not_unique' end as [type]
        , i.[name] as index_name
        , i.index_id
    from sys.objects t
    inner join sys.indexes i
    on t.[object_id] = i.[object_id]
    cross apply (
        select col.[name] + ', '
        from sys.index_columns ic
        inner join sys.columns col on ic.[object_id] = col.[object_id] and ic.column_id = col.column_id
        where ic.[object_id] = t.[object_id]
        and ic.index_id = i.index_id
        order by col.column_id
        for xml path ('')
    ) D (column_names)
    where t.is_ms_shipped <> 1
    and index_id > 0
) X
-- The following where clause prevents the insertion of duplicates
where not exists (
    select 1
    from test.dbo.indexes I
    where I.table_view = X.table_view and I.[columns] = X.[columns] and I.[type] = X.[type] and I.index_name = X.index_name and I.index_id = X.index_id
);

注意：向order by语句中添加insert没有好处，表本质上是无序的，如果顺序很重要，则必须在选择中使用order by。

避免添加重复值

1 个答案: