Optimize “Insert into” in SQL

In this post I will give you some advice on how to extract data from a large table into a new table. In this case we are using the “INSERT INTO” statement. When working with large tables you want to have a query that runs fast and uses as little logging as possible.

Consider this query

USE [AdventureWorksDW2012]

CREATE TABLE [dbo].[FactInternetSales_new](
	[ProductKey] [int] NOT NULL,
	[OrderDateKey] [int] NOT NULL,
	[DueDateKey] [int] NOT NULL,
	[ShipDateKey] [int] NOT NULL,
	[CustomerKey] [int] NOT NULL,
	[PromotionKey] [int] NOT NULL,
	[CurrencyKey] [int] NOT NULL,
	[SalesTerritoryKey] [int] NOT NULL,
	[SalesOrderNumber] [nvarchar](20) NOT NULL,
	[SalesOrderLineNumber] [tinyint] NOT NULL,
	[RevisionNumber] [tinyint] NOT NULL,
	[OrderQuantity] [smallint] NOT NULL,
	[UnitPrice] [money] NOT NULL,
	[ExtendedAmount] [money] NOT NULL,
	[UnitPriceDiscountPct] [float] NOT NULL,
	[DiscountAmount] [float] NOT NULL,
	[ProductStandardCost] [money] NOT NULL,
	[TotalProductCost] [money] NOT NULL,
	[SalesAmount] [money] NOT NULL,
	[TaxAmt] [money] NOT NULL,
	[Freight] [money] NOT NULL,
	[CarrierTrackingNumber] [nvarchar](25) NULL,
	[CustomerPONumber] [nvarchar](25) NULL,
	[OrderDate] [datetime] NULL,
	[DueDate] [datetime] NULL,
	[ShipDate] [datetime] NULL
) ON [PRIMARY]

CREATE NONCLUSTERED INDEX IX_FactInternetSales_new ON dbo.FactInternetSales_new
(
	CustomerKey
) WITH( STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) 
ON [PRIMARY]

DECLARE @t1 DATETIME;
DECLARE @t2 DATETIME;

SET @t1 = GETDATE();
insert into [dbo].[FactInternetSales_new]
select * 
from [dbo].[FactInternetSales]
SET @t2 = GETDATE();
SELECT DATEDIFF(millisecond,@t1,@t2) AS elapsed_ms;

drop table [dbo].[FactInternetSales_new]

The output for this query will be

Insert 1

If I change the query so that the destination table is a heap (no index) and adds the “TABLOCK” query hint I will gain a minimally logged operation. And when the data is over I will create my index.

Lets take a look at the script

USE [AdventureWorksDW2012]

CREATE TABLE [dbo].[FactInternetSales_new_fast_one](
	[ProductKey] [int] NOT NULL,
	[OrderDateKey] [int] NOT NULL,
	[DueDateKey] [int] NOT NULL,
	[ShipDateKey] [int] NOT NULL,
	[CustomerKey] [int] NOT NULL,
	[PromotionKey] [int] NOT NULL,
	[CurrencyKey] [int] NOT NULL,
	[SalesTerritoryKey] [int] NOT NULL,
	[SalesOrderNumber] [nvarchar](20) NOT NULL,
	[SalesOrderLineNumber] [tinyint] NOT NULL,
	[RevisionNumber] [tinyint] NOT NULL,
	[OrderQuantity] [smallint] NOT NULL,
	[UnitPrice] [money] NOT NULL,
	[ExtendedAmount] [money] NOT NULL,
	[UnitPriceDiscountPct] [float] NOT NULL,
	[DiscountAmount] [float] NOT NULL,
	[ProductStandardCost] [money] NOT NULL,
	[TotalProductCost] [money] NOT NULL,
	[SalesAmount] [money] NOT NULL,
	[TaxAmt] [money] NOT NULL,
	[Freight] [money] NOT NULL,
	[CarrierTrackingNumber] [nvarchar](25) NULL,
	[CustomerPONumber] [nvarchar](25) NULL,
	[OrderDate] [datetime] NULL,
	[DueDate] [datetime] NULL,
	[ShipDate] [datetime] NULL
) ON [PRIMARY]

DECLARE @t1 DATETIME;
DECLARE @t2 DATETIME;

SET @t1 = GETDATE();
INSERT INTO [dbo].[FactInternetSales_new_fast_one] WITH (TABLOCK)
select * 
from [dbo].[FactInternetSales]

CREATE NONCLUSTERED INDEX IX_FactInternetSales_new ON dbo.[FactInternetSales_new_fast_one]
(
	CustomerKey
) WITH( STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) 
ON [PRIMARY]

SET @t2 = GETDATE();
SELECT DATEDIFF(millisecond,@t1,@t2) AS elapsed_ms;

drop table [dbo].[FactInternetSales_new_fast_one]

This query will run in about half the time on my laptop

Insert 2

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