I have a relatively large table (currently 2 million records) and would like to know if it's possible to improve performance for ad-hoc queries. The word ad-hoc being key here. Adding indexs is not an option (there are already indexs on the columns which are queried most commonly).
Running a simple query to return the 100 most recently updated records:
select top 100 * from ER101_ACCT_ORDER_DTL order by er101_upd_date_iso desc
Takes several minutes. See execution plan below:
Additional detail from the table scan:
SQL Server Execution Times:
CPU time = 3945 ms, elapsed time = 148524 ms.
The server is pretty powerful (from memory 48GB ram, 24 core processor) running sql server 2008 r2 x64.
Update
I found this code to create a table with 1,000,000 records. I thought i could then run SELECT TOP 100 * FROM testEnvironment ORDER BY mailAddress DESC
on a few different servers to find out if my disk access speeds were poor on the server.
WITH t1(N) AS (SELECT 1 UNION ALL SELECT 1),
t2(N) AS (SELECT 1 FROM t1 x, t1 y),
t3(N) AS (SELECT 1 FROM t2 x, t2 y),
Tally(N) AS (SELECT TOP 98 ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM t3 x, t3 y),
Tally2(N) AS (SELECT TOP 5 ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM t3 x, t3 y),
Combinations(N) AS (SELECT DISTINCT LTRIM(RTRIM(RTRIM(SUBSTRING(poss,a.N,2)) + SUBSTRING(vowels,b.N,1)))
FROM Tally a
CROSS JOIN Tally2 b
CROSS APPLY (SELECT 'B C D F G H J K L M N P R S T V W Z SCSKKNSNSPSTBLCLFLGLPLSLBRCRDRFRGRPRTRVRSHSMGHCHPHRHWHBWCWSWTW') d(poss)
CROSS APPLY (SELECT 'AEIOU') e(vowels))
SELECT IDENTITY(INT,1,1) AS ID, a.N + b.N AS N
INTO #testNames
FROM Combinations a
CROSS JOIN Combinations b;
SELECT IDENTITY(INT,1,1) AS ID, firstName, secondName
INTO #testNames2
FROM (SELECT firstName, secondName
FROM (SELECT TOP 1000 --1000 * 1000 = 1,000,000 rows
N AS firstName
FROM #testNames
ORDER BY NEWID()) a
CROSS JOIN (SELECT TOP 1000 --1000 * 1000 = 1,000,000 rows
N AS secondName
FROM #testNames
ORDER BY NEWID()) b) innerQ;
SELECT firstName, secondName,
firstName + '.' + secondName + '@fake.com' AS eMail,
CAST((ABS(CHECKSUM(NEWID())) % 250) + 1 AS VARCHAR(3)) + ' ' AS mailAddress,
(ABS(CHECKSUM(NEWID())) % 152100) + 1 AS jID,
IDENTITY(INT,1,1) AS ID
INTO #testNames3
FROM #testNames2
SELECT IDENTITY(INT,1,1) AS ID, firstName, secondName, eMail,
mailAddress + b.N + b.N AS mailAddress
INTO testEnvironment
FROM #testNames3 a
INNER JOIN #testNames b ON a.jID = b.ID;
--CLEAN UP USELESS TABLES
DROP TABLE #testNames;
DROP TABLE #testNames2;
DROP TABLE #testNames3;
But on the three test servers the query ran almost instantaneously. Can anyone explain this?
Update 2
Thank you for the comments- please keep them coming… they led me to try changing the primary key index from non-clustered to clustered with rather interesting (and unexpected?) results.
Non-clustered:
SQL Server Execution Times:
CPU time = 3634 ms, elapsed time = 154179 ms.
Clustered:
SQL Server Execution Times:
CPU time = 2650 ms, elapsed time = 52177 ms.
How is this possible? Without an index on the er101_upd_date_iso column how can a clustered index scan be used?
Update 3
As requested- this is the create table script:
CREATE TABLE [dbo].[ER101_ACCT_ORDER_DTL](
[ER101_ORG_CODE] [varchar](2) NOT NULL,
[ER101_ORD_NBR] [int] NOT NULL,
[ER101_ORD_LINE] [int] NOT NULL,
[ER101_EVT_ID] [int] NULL,
[ER101_FUNC_ID] [int] NULL,
[ER101_STATUS_CDE] [varchar](2) NULL,
[ER101_SETUP_ID] [varchar](8) NULL,
[ER101_DEPT] [varchar](6) NULL,
[ER101_ORD_TYPE] [varchar](2) NULL,
[ER101_STATUS] [char](1) NULL,
[ER101_PRT_STS] [char](1) NULL,
[ER101_STS_AT_PRT] [char](1) NULL,
[ER101_CHG_COMMENT] [varchar](255) NULL,
[ER101_ENT_DATE_ISO] [datetime] NULL,
[ER101_ENT_USER_ID] [varchar](10) NULL,
[ER101_UPD_DATE_ISO] [datetime] NULL,
[ER101_UPD_USER_ID] [varchar](10) NULL,
[ER101_LIN_NBR] [int] NULL,
[ER101_PHASE] [char](1) NULL,
[ER101_RES_CLASS] [char](1) NULL,
[ER101_NEW_RES_TYPE] [varchar](6) NULL,
[ER101_RES_CODE] [varchar](12) NULL,
[ER101_RES_QTY] [numeric](11, 2) NULL,
[ER101_UNIT_CHRG] [numeric](13, 4) NULL,
[ER101_UNIT_COST] [numeric](13, 4) NULL,
[ER101_EXT_COST] [numeric](11, 2) NULL,
[ER101_EXT_CHRG] [numeric](11, 2) NULL,
[ER101_UOM] [varchar](3) NULL,
[ER101_MIN_CHRG] [numeric](11, 2) NULL,
[ER101_PER_UOM] [varchar](3) NULL,
[ER101_MAX_CHRG] [numeric](11, 2) NULL,
[ER101_BILLABLE] [char](1) NULL,
[ER101_OVERRIDE_FLAG] [char](1) NULL,
[ER101_RES_TEXT_YN] [char](1) NULL,
[ER101_DB_CR_FLAG] [char](1) NULL,
[ER101_INTERNAL] [char](1) NULL,
[ER101_REF_FIELD] [varchar](255) NULL,
[ER101_SERIAL_NBR] [varchar](50) NULL,
[ER101_RES_PER_UNITS] [int] NULL,
[ER101_SETUP_BILLABLE] [char](1) NULL,
[ER101_START_DATE_ISO] [datetime] NULL,
[ER101_END_DATE_ISO] [datetime] NULL,
[ER101_START_TIME_ISO] [datetime] NULL,
[ER101_END_TIME_ISO] [datetime] NULL,
[ER101_COMPL_STS] [char](1) NULL,
[ER101_CANCEL_DATE_ISO] [datetime] NULL,
[ER101_BLOCK_CODE] [varchar](6) NULL,
[ER101_PROP_CODE] [varchar](8) NULL,
[ER101_RM_TYPE] [varchar](12) NULL,
[ER101_WO_COMPL_DATE] [datetime] NULL,
[ER101_WO_BATCH_ID] [varchar](10) NULL,
[ER101_WO_SCHED_DATE_ISO] [datetime] NULL,
[ER101_GL_REF_TRANS] [char](1) NULL,
[ER101_GL_COS_TRANS] [char](1) NULL,
[ER101_INVOICE_NBR] [int] NULL,
[ER101_RES_CLOSED] [char](1) NULL,
[ER101_LEAD_DAYS] [int] NULL,
[ER101_LEAD_HHMM] [int] NULL,
[ER101_STRIKE_DAYS] [int] NULL,
[ER101_STRIKE_HHMM] [int] NULL,
[ER101_LEAD_FLAG] [char](1) NULL,
[ER101_STRIKE_FLAG] [char](1) NULL,
[ER101_RANGE_FLAG] [char](1) NULL,
[ER101_REQ_LEAD_STDATE] [datetime] NULL,
[ER101_REQ_LEAD_ENDATE] [datetime] NULL,
[ER101_REQ_STRK_STDATE] [datetime] NULL,
[ER101_REQ_STRK_ENDATE] [datetime] NULL,
[ER101_LEAD_STDATE] [datetime] NULL,
[ER101_LEAD_ENDATE] [datetime] NULL,
[ER101_STRK_STDATE] [datetime] NULL,
[ER101_STRK_ENDATE] [datetime] NULL,
[ER101_DEL_MARK] [char](1) NULL,
[ER101_USER_FLD1_02X] [varchar](2) NULL,
[ER101_USER_FLD1_04X] [varchar](4) NULL,
[ER101_USER_FLD1_06X] [varchar](6) NULL,
[ER101_USER_NBR_060P] [int] NULL,
[ER101_USER_NBR_092P] [numeric](9, 2) NULL,
[ER101_PR_LIST_DTL] [numeric](11, 2) NULL,
[ER101_EXT_ACCT_CODE] [varchar](8) NULL,
[ER101_AO_STS_1] [char](1) NULL,
[ER101_PLAN_PHASE] [char](1) NULL,
[ER101_PLAN_SEQ] [int] NULL,
[ER101_ACT_PHASE] [char](1) NULL,
[ER101_ACT_SEQ] [int] NULL,
[ER101_REV_PHASE] [char](1) NULL,
[ER101_REV_SEQ] [int] NULL,
[ER101_FORE_PHASE] [char](1) NULL,
[ER101_FORE_SEQ] [int] NULL,
[ER101_EXTRA1_PHASE] [char](1) NULL,
[ER101_EXTRA1_SEQ] [int] NULL,
[ER101_EXTRA2_PHASE] [char](1) NULL,
[ER101_EXTRA2_SEQ] [int] NULL,
[ER101_SETUP_MSTR_SEQ] [int] NULL,
[ER101_SETUP_ALTERED] [char](1) NULL,
[ER101_RES_LOCKED] [char](1) NULL,
[ER101_PRICE_LIST] [varchar](10) NULL,
[ER101_SO_SEARCH] [varchar](9) NULL,
[ER101_SSB_NBR] [int] NULL,
[ER101_MIN_QTY] [numeric](11, 2) NULL,
[ER101_MAX_QTY] [numeric](11, 2) NULL,
[ER101_START_SIGN] [char](1) NULL,
[ER101_END_SIGN] [char](1) NULL,
[ER101_START_DAYS] [int] NULL,
[ER101_END_DAYS] [int] NULL,
[ER101_TEMPLATE] [char](1) NULL,
[ER101_TIME_OFFSET] [char](1) NULL,
[ER101_ASSIGN_CODE] [varchar](10) NULL,
[ER101_FC_UNIT_CHRG] [numeric](13, 4) NULL,
[ER101_FC_EXT_CHRG] [numeric](11, 2) NULL,
[ER101_CURRENCY] [varchar](3) NULL,
[ER101_FC_RATE] [numeric](12, 5) NULL,
[ER101_FC_DATE] [datetime] NULL,
[ER101_FC_MIN_CHRG] [numeric](11, 2) NULL,
[ER101_FC_MAX_CHRG] [numeric](11, 2) NULL,
[ER101_FC_FOREIGN] [numeric](12, 5) NULL,
[ER101_STAT_ORD_NBR] [int] NULL,
[ER101_STAT_ORD_LINE] [int] NULL,
[ER101_DESC] [varchar](255) NULL
) ON [PRIMARY]
SET ANSI_PADDING OFF
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_PRT_SEQ_1] [varchar](12) NULL
SET ANSI_PADDING ON
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_PRT_SEQ_2] [varchar](120) NULL
SET ANSI_PADDING OFF
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_TAX_BASIS] [char](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_RES_CATEGORY] [char](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_DECIMALS] [char](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_TAX_SEQ] [varchar](7) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_MANUAL] [char](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_TR_LC_RATE] [numeric](12, 5) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_TR_FC_RATE] [numeric](12, 5) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_TR_PL_RATE] [numeric](12, 5) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_TR_DIFF] [char](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_TR_UNIT_CHRG] [numeric](13, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_TR_EXT_CHRG] [numeric](13, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_TR_MIN_CHRG] [numeric](13, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_TR_MAX_CHRG] [numeric](13, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_PL_UNIT_CHRG] [numeric](13, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_PL_EXT_CHRG] [numeric](13, 2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_PL_MIN_CHRG] [numeric](13, 2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_PL_MAX_CHRG] [numeric](13, 2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_TAX_RATE_TYPE] [char](1) NULL
SET ANSI_PADDING ON
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ORDER_FORM] [varchar](2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_FACTOR] [int] NULL
SET ANSI_PADDING OFF
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_MGMT_RPT_CODE] [varchar](6) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ROUND_CHRG] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_WHOLE_QTY] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SET_QTY] [numeric](15, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SET_UNITS] [numeric](15, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SET_ROUNDING] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SET_SUB] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_TIME_QTY] [numeric](13, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_GL_DISTR_PCT] [numeric](7, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_REG_SEQ] [int] NULL
SET ANSI_PADDING ON
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ALT_DESC] [varchar](255) NULL
SET ANSI_PADDING OFF
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_REG_ACCT] [varchar](8) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_DAILY] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_AVG_UNIT_CHRG] [varchar](1) NULL
SET ANSI_PADDING ON
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ALT_DESC2] [varchar](255) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_CONTRACT_SEQ] [int] NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ORIG_RATE] [numeric](13, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_DISC_PCT] [decimal](17, 10) NULL
SET ANSI_PADDING OFF
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_DTL_EXIST] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ORDERED_ONLY] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SHOW_STDATE] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SHOW_STTIME] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SHOW_ENDATE] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SHOW_ENTIME] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SHOW_RATE] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SHOW_UNITS] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_BASE_RATE] [numeric](13, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_COMMIT_QTY] [numeric](11, 2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_MM_QTY_USED] [varchar](2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_MM_CHRG_USED] [varchar](2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ITEM_TEXT_1] [varchar](50) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ITEM_NBR_1] [numeric](13, 3) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ITEM_NBR_2] [numeric](13, 3) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ITEM_NBR_3] [numeric](13, 3) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_PL_BASE_RATE] [numeric](13, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_REV_DIST] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_COVER] [int] NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_RATE_TYPE] [varchar](2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_USE_SEASONAL] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_TAX_EI] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_TAXES] [numeric](13, 2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_FC_TAXES] [numeric](13, 2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_PL_TAXES] [numeric](13, 2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_FC_QTY] [numeric](13, 2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_LEAD_HRS] [numeric](6, 2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_STRIKE_HRS] [numeric](6, 2) NULL
SET ANSI_PADDING ON
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_CANCEL_USER_ID] [varchar](10) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ST_OFFSET_HRS] [numeric](7, 2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_EN_OFFSET_HRS] [numeric](7, 2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_MEMO_FLAG] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_MEMO_EXT_CHRG] [numeric](13, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_MEMO_EXT_CHRG_PL] [numeric](13, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_MEMO_EXT_CHRG_TR] [numeric](13, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_MEMO_EXT_CHRG_FC] [numeric](13, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_TIME_QTY_EDIT] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SURCHARGE_PCT] [decimal](17, 10) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_INCL_EXT_CHRG] [numeric](13, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_INCL_EXT_CHRG_FC] [numeric](13, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_CARRIER] [varchar](6) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SETUP_ID2] [varchar](8) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SHIPPABLE] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_CHARGEABLE] [varchar](2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ITEM_NBR_ALLOW] [varchar](2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ITEM_NBR_START] [int] NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ITEM_NBR_END] [int] NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ITEM_SUPPLIER] [varchar](8) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_TRACK_ID] [varchar](40) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_REF_INV_NBR] [int] NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_NEW_ITEM_STS] [varchar](2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_MSTR_REG_ACCT_CODE] [varchar](8) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ALT_DESC3] [varchar](255) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ALT_DESC4] [varchar](255) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ALT_DESC5] [varchar](255) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SETUP_ROLLUP] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_MM_COST_USED] [varchar](2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_AUTO_SHIP_RCD] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ITEM_FIXED] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ITEM_EST_TBD] [varchar](3) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ROLLUP_PL_UNIT_CHRG] [numeric](13, 4) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ROLLUP_PL_EXT_CHRG] [numeric](13, 2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_GL_ORD_REV_TRANS] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_DISCOUNT_FLAG] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SETUP_RES_TYPE] [varchar](6) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SETUP_RES_CODE] [varchar](12) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_PERS_SCHED_FLAG] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_PRINT_STAMP] [datetime] NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SHOW_EXT_CHRG] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_PRINT_SEQ_NBR] [int] NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_PAY_LOCATION] [varchar](3) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_MAX_RM_NIGHTS] [int] NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_USE_TIER_COST] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_UNITS_SCHEME_CODE] [varchar](6) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_ROUND_TIME] [varchar](2) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_LEVEL] [int] NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_SETUP_PARENT_ORD_LINE] [int] NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_BADGE_PRT_STS] [varchar](1) NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_EVT_PROMO_SEQ] [int] NULL
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD [ER101_REG_TYPE] [varchar](12) NULL
/****** Object: Index [PK__ER101_ACCT_ORDER] Script Date: 04/15/2012 20:24:37 ******/
ALTER TABLE [dbo].[ER101_ACCT_ORDER_DTL] ADD CONSTRAINT [PK__ER101_ACCT_ORDER] PRIMARY KEY CLUSTERED
(
[ER101_ORD_NBR] ASC,
[ER101_ORD_LINE] ASC,
[ER101_ORG_CODE] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 50) ON [PRIMARY]
The table is 2.8 GB in size with index size standing at 3.9 GB.
Best Answer
Simple Answer: NO. You cannot help ad hoc queries on a 238 column table with a 50% Fill Factor on the Clustered Index.
Detailed Answer:
As I have stated in other answers on this topic, Index design is both Art and Science and there are so many factors to consider that there are few, if any, hard and fast rules. You need to consider: the volume of DML operations vs SELECTs, disk subsystem, other indexes / triggers on the table, distribution of data within the table, are queries using SARGable WHERE conditions, and several other things that I can't even remember right now.
I can say that no help can be given for questions on this topic without an understanding of the Table itself, its indexes, triggers, etc. Now that you have posted the table definition (still waiting on the Indexes but the Table definition alone points to 99% of the issue) I can offer some suggestions.
First, if the table definition is accurate (238 columns, 50% Fill Factor) then you can pretty much ignore the rest of the answers / advice here ;-). Sorry to be less-than-political here, but seriously, it's a wild goose chase without knowing the specifics. And now that we see the table definition it becomes quite a bit clearer as to why a simple query would take so long, even when the test queries (Update #1) ran so quickly.
The main problem here (and in many poor-performance situations) is bad data modeling. 238 columns is not prohibited just like having 999 indexes is not prohibited, but it is also generally not very wise.
Recommendations:
ANSI_PADDING OFF
is disturbing, not to mention inconsistent within the table due to the various column additions over time. Not sure if you can fix that now, but ideally you would always haveANSI_PADDING ON
, or at the very least have the same setting across allALTER TABLE
statements.PRIMARY
as that is where SQL SERVER stores all of its data and meta-data about your objects. You create your Table and Clustered Index (as that is the data for the table) on[Tables]
and all Non-Clustered indexes on[Indexes]
WHERE
condition, then consider moving that to the leading column of the clustered index. Assuming that it is used more often than "ER101_ORD_NBR". If "ER101_ORD_NBR" is used more often then keep it. It just seems, assuming that the field names mean "OrganizationCode" and "OrderNumber", that "OrgCode" is a better grouping that might have multiple "OrderNumbers" within it.CHAR(2)
instead ofVARCHAR(2)
as it will save a byte in the row header which tracks variable width sizes and adds up over millions of rows.SELECT *
will hurt performance. Not only due to it requiring SQL Server to return all columns and hence be more likely to do a Clustered Index Scan regardless of your other indexes, but it also takes SQL Server time to go to the table definition and translate*
into all of the column names. It should be slightly faster to specify all 238 column names in theSELECT
list though that won't help the Scan issue. But do you ever really need all 238 columns at the same time anyway?Good luck!
UPDATE
For the sake of completeness to the question "how to improve performance on a large table for ad-hoc queries", it should be noted that while it will not help for this specific case, IF someone is using SQL Server 2012 (or newer when that time comes) and IF the table is not being updated, then using Columnstore Indexes is an option. For more details on that new feature, look here: http://msdn.microsoft.com/en-us/library/gg492088.aspx (I believe these were made to be updateable starting in SQL Server 2014).
UPDATE 2
Additional considerations are:
INT
,BIGINT
,TINYINT
,SMALLINT
,CHAR
,NCHAR
,BINARY
,DATETIME
,SMALLDATETIME
,MONEY
, etc) and well over 50% of the rows areNULL
, then consider enabling theSPARSE
option which became available in SQL Server 2008. Please see the MSDN page for Use Sparse Columns for details.