Sql server 忽略非聚集索引
我有Sql server 忽略非聚集索引,sql-server,azure-sql-database,Sql Server,Azure Sql Database,我有存档的\u事件表,其中包含以下索引 CREATE NONCLUSTERED INDEX [IX_archived_events_5] ON [dbo].[archived_events] ( [account_id] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLO
存档的\u事件表,其中包含以下索引
CREATE NONCLUSTERED INDEX [IX_archived_events_5] ON [dbo].[archived_events]
(
[account_id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON)
GO
ALTER TABLE [dbo].[archived_events] ADD CONSTRAINT [PK_archived_events] PRIMARY KEY CLUSTERED
(
[event_type] DESC,
[id] DESC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON)
GO
问题是,当我执行以下查询时,我在执行计划中看到它对[PK_归档的_事件]进行Clusterd索引扫描
SELECT *
FROM archived_events ae WITH(nolock)
WHERE ( 30 = ae.[account_id] )
非聚集索引被忽略的原因是什么
另请注意,这是SQL Azure,不确定它是否重要。该表的nvarchar(max)列干扰了索引。我已经将它们转换为nvarchar(n),索引现在可以工作。表中有多少行?有多少匹配项30=ae.[account\u id]
?@MartinSmith 400万行…@MartinSmith 717536 match 30=ae.[account\u id]这是表格的18%,所以它可能只需要扫描大约50行就可以得到前10名。如果您尝试使用更具选择性的谓词会怎么样?@MartinSmith我尝试过许多查询,它的行为总是相同的。