Video: Create relationships with the Lookup Wizard - Access
Creating a lookup field in your Microsoft Office Access tables can help improve the efficiency of the data entry Click the Lookup & Relationship datatype. Create Office Access Project applications that use an OLE DB connection to version of the Jet database engine, named the Office Access Connectivity Engine (ACE), . on the Office Access link itself, without affecting the linked SQL Server table. when the append query runs, populating the lookup table with fresh data. An access control list (ACL) is a list of access control entries (ACE). Each ACE in an ACL identifies a trustee and specifies the access rights.
Assign a password to a database. Only users who know the password can open the database. Contents of the database can be encrypted at the file level. Unfortunately, these mechanisms are neither robust nor reliable. Database passwords use a very simple encryption mechanism. In fact, removing an Access database password is simple matter given that free and commercial password "removers" are easily found on the web.
While Access users may not be concerned about such lapses, IT managers certainly should be. While Jet Workgroup Security is more robust, it still leaves the contents of the entire MDB database open from the file system.
Since all table data and code is stored in plain view, it is a trivial matter to open an MDB file in a string-compatible editor and view code, passwords, and table data. Finally, because Access requires full read permissions for all users to the actual database file, anyone who can see a shared network drive can walk off with the database on a disk or CDR or email it outside of your organization.
If Security is of importance, SQL Server is much more secure than Microsoft Access, Excel, Word or any other program that stores its files directly on the hard disk accessible to the user.
Reliability and Maintenance Reliability is one of the key benchmarks to examine when considering upsizing. Indeed, for many mission critical applications, reliability is the most important consideration. A corrupt database generally locks out all users of the database and results in data loss and business disruption.
If any one of those users unexpectedly loses the connection, the database can become corrupt. Third party repair services are available, but this requires sending the affected database off to another location, paying a fee, and waiting for it to be returned with mixed results. Maintenance Issues Windows allows copying a Microsoft Access database even if people have it open, so you can create a backup, but that may be a problem if someone is modifying the data at the time the file is being copied.
In a multi-user environment, Microsoft Access does not tell you who is currently in the database, so it can be an administrative headache to get people off the system.
Our Total Access Admin program lets you monitor the users going in and out of the database in real-time, which helps and can compact the database after everyone exits, but it's not a built-in feature of Microsoft Access. It is often difficult to coordinate the process of ensuring all users log off of an Access application before making a backup. Typical scenarios involve users leaving their computers on when they leave the office for the day. This leaves the database open and backup software will not be able to reliably copy the database file.
Often this is only detected after the backup fails, leaving the system administrator to track down the problem and hope it is resolved before the next backup runs.
It does not automatically reclaim lost database space or optimize indexes and queries. Our Total Visual Agent program lets you automate this on a schedule you specify and maintain an audit trail, but it's not a built-in feature of Microsoft Access. If an organization doesn't regularly backup individual desktop databases, people may create Access databases on their PCs that are never backed up or maintained. Organizations can treat them as user data that can be lost as if it were an Excel spreadsheet or Word document, but better policies should be in place so users can save their databases where basic system administration is provided.
Microsoft Access databases need to be backed up for disaster recovery and periodically compacted to remain healthy. An automated system should be implemented to take care of that for the many Access databases that exist today and those created in the future.
SQL Server upsizing should be considered for the databases where such automated processes cannot be implemented due to continuous use of the database or the cost of losing any data is high.
Scalability Scalability is defined as the ability of an application to operate in an acceptable manner as the number of users or processes calling the application increases. This separates the user application database from the back-end shared data database. The front-end application database links to the shared database and upgrades are easier because the data does not need to be modified for new releases provided tables structures aren't modified.
The split database architecture will also help in an upsizing endeavor to preserve the existing Access front-end. If a single copy of a Microsoft Access database resides on a network drive and is being opened by multiple users at one time, you may have a scalability issue. But that should be addressed by using a split database architecture rather than upsizing to SQL Server. Number of Concurrent Users There have been myths about Microsoft Access databases not being able to support more than a 20 users.
That may have been the case when Microsoft Access was introduced inbut that has NOT been the case for quite some time. Microsoft Access technically allows up to connections per database. That means it can be used for applications for teams many times that if they don't all need to use it at the same time.
On the other hand, a poorly designed Access application can run at a crawl with two users. Or some processes are just time consuming and will be slow no matter what database is used. Keep this variable open as long as your application is running. This forces Access to keep that database open, making access to linked tables much faster. This data access method is more efficient for adding records because existing records are not read from the database. Create a Data Entry Form If you often have the need to add new records to a linked table, consider creating an "Add Records" form and set that form's DataEntry property to Yes.
This prevents Access from attempting to retrieve all the existing records in a linked table when you need is to enter new records. Limit the Data Returned by Queries Limit the number of fields and records returned by using filters or queries. This reduces the amount of data that needs to be read from the linked table, thereby according faster performance. Don't Use Domain Aggregate Functions If a query is based on one or more linked tables, avoid using functions built-in or user-definedor domain aggregate functions in the query criteria.
When you use domain aggregate functions such as DLookupAccess must fetch all records in the function's data source to execute the query. Release Locks ASAP To improve multi-user concurrency, assume that other users will be trying to edit data in the same linked tables that you are using. In other words, keep records locked only as long as is necessary.
This makes opening that table much faster in subsequent attempts. This is because linked tables cache a lot of information about the source table in your database, making the retrieval of the same structural information unnecessary after the linked table is created. Minimize Server Traffic Minimize the amount of data returned from the server. Do this by structuring your queries to return only the fields and records needed. Use Snapshots When Appropriate Don't open Dynaset type recordset object on SQL database tables unless you need to add or edit records, or need to see the changes made by other users.
Instead, consider using Snapshot recordsets which can be faster to scroll through. Of course, Snapshot recordsets can take longer to open since they require a full read of the source data. Snapshot type recordsets must load all records from the data source before becoming available, whereas Dynasets are available as soon as the first 20 or so records are retrieved.
Also, when using a Snapshot against large ODBC data sources, you run the risk of running out of disk space on your local computer. Then, the database engine creates a temporary database to store the contents of the snapshot. In a nutshell, when you open a snapshot, you need at least as much disk space as the largest table you are opening. Microsoft Access forms and reports have automatic caching mechanisms. Don't Force Local Query Processing Don't use query constructs that cause processing to be done by Access on the local computer.
The following query operations force the Jet database engine to perform local data processing: Join operations between table that are linked to different data source I.
Outer joins that contain syntax that is not directly supported by the remote database server. The "application" part of your database holds all objects except tables, and is linked to the "data" part that contains the actual tables.
MDA created with a previous version of MS Access, convert it to the current version of Access for optimum performance.
Table Relations and Blanks
Use the Access Performance Analyzer Microsoft Access has a useful performance tool built right into the product. From the Tools menu, select Analyze, Performance.
The Performance Analyzer allows you to select all objects or specific objects, and then runs an analysis looking for potential problems. The Performance Analyzer does not find all of the items that Total Access Analyzer does, but it does offer some tips. Run the Microsoft Access Table Analyzer The Access Table Analyzer makes it easy to properly normalize the data in your tables by breaking tables with repeated or improperly structured data into two or more tables.
This tool is available from the Access Tools, Analyze menu Reduce the Size of Graphics in your Microsoft Access or Later Databases If you embed graphics on your forms or reports, Access or later can store them much more efficiently.
Access can convert graphics into much smaller PNG formats to significantly reduce the size of your databases. This does not affect graphics already on your forms and reports but helps if you add new graphics or replace existing ones. To activate this feature, change an Access setting. Preserve source image format smaller file size Compact Your Database Often To Reclaim Space Compacting your database reclaims unused space and makes almost all operations faster.
You should do this on a regular basis. Also, be sure to compact anytime you import or delete objects in your database, or compile and save VBA code.
Optimizing Microsoft Office Access Applications Linked to SQL Server
Learn more about Total Visual Agent for a system administrative tool to schedule compact and backup your Access databases on a regular schedule. Make It Look Faster If you have exhausted all other performance optimization techniques, consider making your application "look" faster. Do this by displaying status messages and progress meters as your application loads forms, runs queries, and performs any other operation that may take a bit of time.
While this doesn't make your application run faster, it appears to run faster. When you compact the database, you reorganize records so that they are stored in adjacent spaces, making retrieval faster. Additionally, compacting a database updates its data statistics, which can be used by a query to run faster. You can force a query to recompile which in turn causes it to use the latest statistics by opening it in design view, saving it, and then running it.
You may want to defragment your disk using a program such as the Disk Defragmenter that is part of Windows before compacting your database. This leaves contiguous free disk space immediately after the database file. In theory, this make future additions to the database occur faster. You may want to experiment with this on your system. Index the fields on both sides of a join. Alternatively, you can create a relationship between joined fields, in which case an index is automatically created.
Search Access Help for: Limit Fields Returned by a Query Where possible, limit the number of fields returned by a query. This results in faster performance and reduced resource usage. Pay special care to avoid the use of immediate If IIF functions in sub-queries.
Don't Use Non-Indexed Fields for Criteria Avoid using non-indexed fields or calculated fields for criteria restrictions. Index Sort Fields Index any fields you use for sorting. Be careful not to over-index. Use Temporary Tables to Eliminate Running the Same Queries Over and Over If you are processing data that's used multiple times for instance on multiple reportsit may be faster to store intermediate results in temporary tables rather than running a series of Select queries many times.
Create a temporary table to store your results. Empty the table and fill it with your data using and Append query. You can then use that table for multiple reports and forms. Avoid Domain Aggregate Functions on Foreign Tables Do not use domain aggregate functions DLookup for example in queries to access data from a table that is not in the query. Link to the table and set criteria accordingly, or create a separate aggregate totals query.
When you then run a query, these updated statistics are compiled in the query's execution plan. This sequence of events results in the fastest possible query. Before you deliver your application, compact the database, and then force each query to be recompiled. Other linked data types do not support Rushmore optimization. To ensure that Rushmore optimizations are used, create indexes on all fields that are used to restrict a query's output.
If you have queries that don't contain indexes on fields used in the query's restriction clause, Rushmore is not used. Link on Primary Key Indexes Whenever Possible To make queries run faster, you should have indexes on all fields in the query that join, restrict, or sort the data.
Whenever possible, link on Primary Key fields instead of other fields. Indexes are most critical on tables with large numbers of records, so you may not see a difference on small tables. You also don't need to add secondary indexes on fields that are part of referential integrity. Experiment With One-to-Many Restrictions If you have a one to many join in query with a restriction, try moving the restriction to the other side of the join.
For example, if the restriction is on the many side, move it to the one side.
Optimizing Microsoft Office Access Applications Linked to SQL Server
Compare performance results for both versions, and choose the fastest one. De-Normalize If Necessary Although you should strive to normalize your data for best performance and future flexibility, you may want to consider denormalizing some of your data if you frequently run queries with joins would benefit from such data restructuring. Experiment With Sub Queries Instead Of Joins If you have a query with a join that is not performing adequately, consider replacing the join with a sub query.
In some cases, the sub query may cause the overall query operation to run faster.
database design - Look-up vs relationship Microsoft Access - Stack Overflow
Limit the Number of Fields Returned By Each Query Where possible, queries should use a Where clause to constrain, or limit, the number of records returned. Somehow, saved queries are optimized more than the SQL string behind the report. Close Unused Forms Close forms that aren't being used. Every form that is open consumes memory that could be used by other parts of your applications. Open Forms Hidden Consider opening your application's most commonly used forms when your application starts.
Set their Visible properties to False, and then make the Visible as needed.
This frontloads some performance hits to the application load event, making forms load faster when needed. Use the DataEntry Property of a Form If a form's record source the table or tables accessed by the form's RecordSource property contain a large number of records, and the form is primarily used to add new records, set the DataEntry property of the form to Yes. This precludes Access from having to retrieve existing records when the form loads.
Don't Sort A Form's Recordset Avoid sorting records in a form's underlying record source unless a particular presentation order is absolutely necessary for the form. This makes the form load faster. By doing this, you can use the query to restrict the number of fields returned, making the form load faster. Use Lightweight Forms Consider replacing Visual Basic code in a form's module with calls to standard modules, or with hyperlink objects.
Then set the form's HasModule property to False. This turns the form into a Lightweight form, making it load faster. Search Access online help for "Lightweight Forms" for more information. In Accessyou can use embedded macros for simple operations. Also index all fields in the subform that are used for criteria. Or set the RecordsetType property of the subform to Snapshot.
In order to find matches, Access needs to convert numeric values to text.Microsoft Access 2016 Tutorial: Linking the Tables and Defining the Relationships
If the data type is Text, this conversion can be skipped. Optimize Bound ComboBoxes If the bound field in a lookup combobox is not the displayed field, don't use expressions for the bound field or the displayed field, don't use restrictions the WHERE clause in the row source, and use single-table row sources wherever possible. Move Linked Data Local for ComboBox and ListBox Controls If the data that fills a list box or combo box does not change often, and that data comes from a linked table, consider moving that data's table into the local database.
This can be a huge performance boost, especially if the linked table is located on a network drive. When the form loads, prepare only the controls on the form's first page. If you are using a version of Office Access prior to Office Accessnavigate to the following registry key, which appears as a folder in the Registry Editor.
If you are using Office Accessnavigate to the following registry key. If Office Access is open when you make this change, you must close and reopen Office Access for the change to take effect. After making this change in the registry, queries submitted to any ODBC data source are logged in a text file named Sqlout.
Unless you delete this file or its contents, it continues to grow as new queries are executed and the tracing activity degrades performance. It is very important to return to the Registry Editor and turn the feature off by changing the TraceSQLMode setting back to 0 when you are done testing. Running SQL Profiler also has a negative impact on performance, so try to avoid using it on a production server and close your Profiler traces when you are done testing.
Before you can make productive use of these diagnostic tools, you must understand how Office Access interacts with SQL Server. Without that understanding, the SQL statements that you see in Profiler traces and in Sqlout logs can be quite puzzling.
Suppliers, and that explicitly names the three columns in the table. Instead, both the Sqlout. The following is what is written to Sqlout. All the quotation marks that you see around object names are comparable to the brackets that Office Access uses and that also can be used in SQL Server to handle spaces or other illegal characters in names.
The question marks are placeholders for parameters. A Profiler trace shows the three corresponding Transact-SQL statements that are processed on the server. In the first step, Office Access picks a "bookmark" column or set of columns, which is usually the table's primary key but could be based on any unique index, and retrieves just those values for every row in the table or query. This is often referred to as a keyset. Then Office Access prepares a parameterized SQL statement to select all the columns in the table or query for 10 rows at a time.
The final step is to execute this statement, which is assigned a number on the server 6 in the exampleas many times as needed, passing in 10 bookmark values at a time.
If there are two columns in the bookmark, 20 values are passed in at a time to specify the next 10 rows.