Insert select需要87S,Select出来才只要10S,求解.该如何处理

Insert select需要87S,Select出来才只要10S,求解.
越来越对数据库这块感兴趣了.求解.

顺便再问一句,建立索引之后是不是数据的插入速度会慢许多....

SQL code

    SELECT        DISTINCT        C.[Firm Name],        C.[Address Line 1] + ' ' + C.[Address Line 2],        C.[City],        C.[State],        C.[Zip Code],        C.[Bus# Phone Number],        C.[Bus# FaxNumber],        C.[Email],        C.[Contact First Name],        C.[Contact Last Name],        @source,        GETDATE(),        @agencyID        FROM dbo.CADBEImportData AS C LEFT JOIN AgencyCertifiedCompanies AS A        ON C.[Firm Name] = A.[CompanyName] AND A.[Source] = @source        WHERE A.[CompanyName] IS NULL AND C.[Firm Name] <> ''

SQL code

    INSERT INTO AgencyCertifiedCompanies(        [CompanyName],        [Address],        [City],        [State],        [Zip],        [Phone],        [Fax],        [Email],        [ContactFirstName],        [ContactLastName],        [Source],        [AddedDate],        [CertificationIssuerID]    )     SELECT        DISTINCT        C.[Firm Name],        C.[Address Line 1] + ' ' + C.[Address Line 2],        C.[City],        C.[State],        C.[Zip Code],        C.[Bus# Phone Number],        C.[Bus# FaxNumber],        C.[Email],        C.[Contact First Name],        C.[Contact Last Name],        @source,        GETDATE(),        @agencyID        FROM dbo.CADBEImportData AS C LEFT JOIN AgencyCertifiedCompanies AS A        ON C.[Firm Name] = A.[CompanyName] AND A.[Source] = @source        WHERE A.[CompanyName] IS NULL AND C.[Firm Name] <> ''

SQL code

CREATE TABLE tablename(id int)insert into tablenameselect 1select * from tablename