Moving from Access Databases to a Visual Studio/SQL Server Solutions Andrew Couch UK Access User Group asc associates

Phases Migrating the database design and data to SQL Server, re- linking Access application to SQL Server Migrating queries to views and stored procedures, also re- packaging the SQL behind Forms and Reports to SQL Server if targeting to Visual Studio. Performance tuning or to make the next step. Migrating the application to use web forms and report services with Visual Studio

Migrating the Database Design and Data

Preparing the Database Design Access Design Tables & Fields Add missing defaults for Boolean fields Avoid zero-length string anomaly Add timestamps (recommended) Add auditing fields (nice opportunity to add at this point) Decide on specific data type mappings; memos to VARCHAR(MAX) or TEXT, OLE Objects to VARBINARY(MAX) or IMAGE and setting decimals precision Relationships Correct for cycles removing cascade operations from relationships (

Preparing the Database Design (2) Table validation rules (checks) Translate Access expressions and functions Field validation rules (checks) Translate Access expressions and functions Indexes Reject inefficiencies, 20% rule Check indexing on foreign key fields Check for primary keys, add if absent Map unique indexes that ignore nulls to unique index and trigger

Schemas and Synonyms

Architecture : Schemas/Security Schemas Group together design objects Partioning designs Combining Access databases Synonyms required for ease of reference Security Database roles Grant permission on schemas Assign users to roles User database roles schemas

Preparing Data Issues Missing data in a required field, fix data or make field allow nulls, no workaround beyond this Violation of other checks (validation rules), avoid by adding checks after data migrated, or fix the data, adding checks after migration gets around some of these issues Date range problem and invalid dates, fix the data, no work around Violation of R.I and deep seated corruption, difficult to generalise, migrate data, remove bad data then add relationships

Migration Sequence Initial Migration Migrate optimised and corrected structure Check and fix data Migrate data Add checks, triggers, indexing and relationships Commissioning Check and fix data Drop checks, triggers, indexing and relationships Empty data Migrate data Add checks, triggers, indexing and relationships

Skills : SQL Server a new world ? A more important system ? Dbas, support, security and reviews of changes to design Production and development environments More developers Better control Version Control Comparing Development and Production Script files to transfer change, GUI dangers in production environments!

Skills : SQL Server a new world ? (2) Other Issues Backups Server Tuning Security Access Application Could stop here and retain the Access front-end Tune SQL converting as required to SPs, Views and Pass Through Or we can go on and do further bulk conversions Do all your existing queries work? Do you need all your existing queries ?

Migrating queries and re-packaging the SQL behind Forms and Reports

Screen Control Example SELECT BigCustomers.Country, BigCustomers.* FROM BigCustomers WHERE (((BigCustomers.Country)=[Forms]![frmPrompt]![txtCountry]));

Parameter Table & View CREATE TABLE tblParameters( SelectedCountry VARCHAR(15), SelectedDate DATETIME, SelectedRegion VARCHAR(15), UserName VARCHAR(128) DEFAULT suser_name() ) CREATE VIEW vw_tblParameters AS SELECT * FROM tblParameters WHERE UserName = suser_name()

Translated View CREATE VIEW vw_ResultsSimple AS SELECT * FROM BigCustomers CROSS JOIN vw_tblParameters WHERE [Country] = [SelectedCountry] SELECT BigCustomers.Country, BigCustomers.* FROM BigCustomers WHERE (((BigCustomers.Country)=[Forms]![frmPrompt]![txtCountry]));

Another Example; optional start SELECT IIf(Not IsNull([Forms]![frmPrompt]![txtTheDate]), IIf([Forms]![frmPrompt]![txtTheDate]<[Date],1,0),1) AS Expr1, IIf(Not IsNull([Forms]![frmPrompt]![txtCountry]), IIf([Forms]![frmPrompt]![txtCountry]=[Country],1,0),1) AS Expr2, BigCustomers.* FROM BigCustomers WHERE (((IIf(Not IsNull([Forms]![frmPrompt]![txtTheDate]), IIf([Forms]![frmPrompt]![txtTheDate]<[Date],1,0),1))=1) AND ((IIf(Not IsNull([Forms]![frmPrompt]![txtCountry]), IIf([Forms]![frmPrompt]![txtCountry]=[Country],1,0),1))=1));

Making Parameters Optional CREATE VIEW vw_Results AS SELECT * FROM BigCustomers CROSS JOIN vw_tblParameters WHERE COALESCE ([Country], ' ') = COALESCE ([SelectedCountry], [Country], ' ') AND COALESCE ([Date], ' 1/1/1900') >= COALESCE ([SelectedDate], [Date], '1/1/1900')

Translating SQL We choose here to consider maximising translation of objects to SQL Server objects, rather than embedding SQL in code Stored Procedures Views Access Support Library Custom UDF Translation Parameter Translation Form/Report Control and Record Source re-packaging SQL

INSERT, UPDATE, DELETE Stored Procedure (need to use pass-through queries to call these by name) Pass-Through Query; containing explicit SQL SELECT, CROSSTAB View (need to indicate unique fields to make these updateable, where possible, can be linked just like tables) Stored Procedure (read-only, can not be linked need to use pass-through queries to call these) Pass-Through Query (read-only); containing explicit SQL What Queries Translate To

References Nested Queries (Calculations) Work out how many layers are going to be required, and then decide whether it would be better to generate a results table using selection criteria, upon which to base the calculations or work with the Nested Query. Parameters Table (Parameters) Isolate all the screen references and parameter statements and use a table containing parameters to filter the SQL, Conversion of IIF statements to CASE statements and use of COALESCE functions for optional parameters.

Migrating the Application

Access Application Objects Menus, Toolbars and Navigation Forms Reports Macros, Modules and Form/Report Module Code

Architecture : Web Forms a Strategy Simple bound controls and templates Web site menu Master Pages and style sheets Further points to consider Screen layouts and screen areas Searching and filtering data

Example Converted Form

Sitemap

Master pages and Content Areas

CSS to Control Presentation

Searching and Filtering

Application Issues We are only considering the use of bound controls with custom templates here Inconsistent data in fields invalid drop-down box selections invalid radio button selections Error handling error handling is a necessity

Application Issues (2) Grid control when inserting data Searching and filtering for data Locking problems No support for timestamps on bound controls Security strategies Internet Integrated security ASP. net security

Report Services Easy security with groups Forms to prompt Launching using ReportViewer controls Import Access reports into a Visual Studio Report Server project

Report Server

Skills : Lost Count Now? New technology areas SQL Server Visual Studio web forms and.net Report Server IIS Challenges for newcomers Security And security

MUST Download a trial version from Site contains a number of technical articles, expanding on these topics