Microsoft Access Query Tips and Techniques with SQL and VBA Code. Luke Chung, President of FMS, Inc. This paper is featured on: Overview.

1. It is based on testing performed at Microsoft.
2. Microsoft Access is a database creation program that allows for anyone to easily maintain and edit a database. It is suitable.

When you need a flexible way to filter a form or report on multiple values, a fixed query isn't your best bet. Find out how you can use a VBA function to add a.

Microsoft Access is the most popular Windows database program. A primary reason for its success is its interactive query interface. Once data is collected in a database, analysis and updates need to be performed. Queries offer the ability to. Mastering Microsoft Access queries will improve your ability to manage and understand your data and simplify application development. Examples are for Microsoft Access 2.

Also applies to Microsoft Access 2. Queries Hide the Complexity of Microsoft Access SQL Syntax. The visual representation of tables and the graphical links between them makes Microsoft Access queries extremely easy to use and hides the complexity of writing the raw Microsoft Access SQL.

Fortunately, the nice user interface still allows. The entire query engine is modeled on SQL systems and can switch between the graphical query design and SQL syntax. Many Microsoft Access users and developers learned SQL from this feature. Knowing the many features of Microsoft Access queries allows you to perform advanced analysis quickly without programming. This presentation covers the basics of queries revealing a variety of subtleties. It quickly moves to more advanced.

Finally, programmatic use of queries is presented: Download Sample Microsoft Access Query Database (1. K)Query Types. Microsoft Access supports many types of queries. Here is a description of the major categories: Select Queries. Retrieve records or summaries (totals) across records. Also includes cross- tabulations.

Make Table Queries. Similar to Select queries but results are placed in a new table. Append Queries. Similar to Select queries but results are added to an existing table.

Update Queries. Modify data in the records. Delete Queries. Records are deleted from a table. Select queries are the most common queries and can be used for viewing and a data source for forms, reports, controls, and other queries. You can choose the fields from a table to display. In the most cases, while viewing the query results you can modify.

These updateable views are extremely powerful. Selecting Table and Fields The first step in creating a query is to specify the table or tables to use and the fields to display. Selecting tables is simple.

The selected table is placed on the upper portion of the query design window. From there you can select the fields for the query. Shift- Click or Ctrl- Click) and dragging them to.

QBE) grid. Make sure the Show option is checked to display the field. Sorting and Reordering Fields Once the fields are placed on the QBE grid, you can reorder the fields by clicking on the column and dragging it to the place you want.

You can choose Ascending or. Descending order. Note that you can turn off the Show setting and sort on a field that does not appear in the display. Renaming Fields A very nice feature of Microsoft Access queries is the ability to rename fields. You may have your data stored in field names that are. By using a query expression, you can change the field name the user sees.

Using Calculated Fields (Expressions) In addition to retrieving fields from a table, a Select query can also display calculations (expressions). Expressions are extremely powerful and allow you. There is an Expression Builder that simplifies the selection of fields and functions.

By default. expression fields are named . Expression fields are also useful for sorting your records. Here's an example of using a calculated field to.

Sort on Multiple Date (or Numeric) Fields with Blank Values in a Microsoft Access Query. Setting Query Properties While designing a query, you can choose View . Description. This property lets you provide a description for the query to help you remember its purpose. Default View. Show the results in a datasheet like a table, or a pivot chart or pivot table.

Output All Fields. This option is usually set to No. If it is changed to Yes, all the fields of all the tables in the query are shown. Top Values. Rather than retrieving all records, you can specify the top n records or n percent, where n is the value specified here. Unique Values. By default this is set to No and all records are retrieved. If this is changed to Yes, every record retrieved contains unique values.

SQL uses the SELECT DISTINCT command). That is, no retrieved records are identical. For instance, you can run a query for the State field of the Patient table. With this set to No, the result is a record for each patient.

When set to Yes, the query is not updateable. Unique Records. By default this is set to No and all records are retrieved. For one table queries, this property is ignored.

For multi- table queries, if it is set to Yes, (similar to using a DISTINCTROW in a SQL statement) only unique records in the underlying tables are retrieved. The Unique Records and Unique Values properties are linked and only one can be set to Yes (both can be No). When both properties are set to No, all records are returned.

Difference between DISTINCT vs. DISTINCTROW These options sometimes appear to provide the same results, but there are significant differences.

DISTINCT checks the results of query and eliminates duplicate rows. These queries (Unique Values = Yes) are not updateable.

This is similar to. Totals Query (e. g. For more information, read our paper addressing the warning message you see. This Recordset is not updateable: Dealing with non- updateable queries in Microsoft Access.

SQL Server Properties. There are several properties related to SQL Server tables and are more technical and rarely need to be modified. Filter, Order By, Filter On Load, Order By On Load. Like a form, you can specify the Filter and Order By settings for a query. However, this is usually part of the query's SQL statement.

There is a significant performance cost for having subdatasheets, so only add them if you want them. Setting Field Properties. In addition to query properties, each field also has properties that can be set. Move to a field in the QBE grid and right click. The most important properties are for numeric and date fields. You can also view the SQL equivalent. Setting Criteria.

The bottom section of the QBE grid is several rows for Criteria. These are optional entries to specify which records are retrieved. To further. narrow the scope, you can enter criteria for several fields. Multi- Field Query Criteria. Entering criteria on the same row for several fields performs an AND query between the fields. If criteria is placed in different rows, an OR.

OR criteria in field 2, etc. Criteria Types. The simplest criteria is the exact match. Just enter the value desired in the field's criteria section. And . You can also retrieve records where a field does not have a particular value by using . To select records with values between two values, use the BETWEEN . Nulls. To select records with Null values, enter Is Null. The opposite is Is Not Null.

For text fields, remember that zero length strings (. OR and IN(., ., .)To select records where a field can have one of several values, use the OR command. You can simply say: .

The second syntax is easier if you. Of course, if you have a very large number of values, it is better to keep those values in a table and link your query to it. Wildcard Searches. Sometimes, you need to search for a particular letter or digit.

Combined with the Like command, wildcards let you specify such criteria. Single Character * Any number of Characters # Single Digit . The. opposite of this (all values that do not have . Finally, to select a range of letters (say . To search for a wildcard character, enclose the value in brackets. For instance, to find values that end in a question mark, use this: Like . In such cases, where the filter values are not known until runtime.

When these queries are run, the user is prompted for the value of each parameter. Using parameters in queries is extremely powerful and converts static . The use of parameters can significantly reduce the.

Optimizing Microsoft Office Access Applications Linked to SQL Server. Andy Baron. November 2. Applies to: Microsoft SQL Server 2. Summary: One way to create applications that use Microsoft Office Access for creating user interfaces and that use Microsoft SQL Server for data storage is to link Office Access tables to SQL Server tables. This is the type of application created by using the SQL Server Migration Assistant for Office Access. This white paper presents techniques for improving performance and updatability in Office Access applications that use tables linked to SQL Server.

The most common way this is done is by creating linked tables in Office Access that use the SQL Server ODBC driver to connect to tables in SQL Server databases. The SQL Server Migration Assistant (SSMA) for Office Access enables you to convert an Office Access database to this type of application by moving your Office Access data to new SQL Server tables and linking to these tables.

Any forms, reports, queries, or code that previously worked with the original Office Access tables are automatically connected to the new SQL Server tables. In an application that uses linked SQL Server tables, two different database engines are at work: the Office Access/Jet database engine that runs on the Office Access client and the SQL Server database engine. The interaction of these two engines can sometimes yield results that are inferior to those obtained by using only the Jet database engine with native Office Access tables.

This white paper discusses several of these issues and presents strategies for resolving them. Most of these issues relate to performance or updatability.

Understanding and Addressing Performance Issues. Developers often migrate data to SQL Server expecting an improvement in application performance.

Although performance does often improve, there are many cases where it remains the same or even degrades. In some cases, performance of certain queries degrades to an unacceptable level. The major cause of query performance degradation is when a query involving very large tables requires that all of the data from one or more tables be downloaded to the client. This can happen even when joins or criteria appear to limit the result set to a small number of records.

This occurs because sometimes the Office Access database engine determines that it cannot submit an entire query to SQL Server. Instead, it submits multiple queries, often including queries that request all of the rows in a table, and then it combines or filters the data on the client. If the criteria require local processing, even queries that should return only selected rows from a single table can require that all the rows in the table be returned. The primary strategy for improving performance is to minimize the amount of data returned to the Office Access client and maximize the amount of processing that occurs on the server. To accomplish this, you need to be able to analyze the SQL commands that Office Access is submitting. Diagnostic Tools. There are two tools that you can use to see how Office Access is communicating with SQL Server.

To listen in on the conversation from the server side, you can open the SQL Server Profiler and create a new trace. Select a template that shows TSQL to see all the statements being processed by the server. From the client side, you can edit a Microsoft Windows registry setting that allows you to see the commands that the Office Access database engine is submitting to ODBC. As always, be very careful when editing the Windows registry. For more information on backing up and editing the registry, see How to Modify the Windows Registry.

To enable tracing of all ODBC commands from the Jet database engine. From the Windows Start menu, select Run. Type Regedit to open the Registry Editor. If you are using a version of Office Access prior to Office Access 2. Registry Editor. If you are using Office Access 2.

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 Trace. SQLMode 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. Cat With A Bow Golf Hacked Game on this page. Understanding Dynasets.

When you observe how Office Access communicates with SQL Server over ODBC, you will notice that most queries are executed very differently from the way you would expect. For example, if you migrate the Northwind data to SQL Server, link to the tables, and open the Shippers table in datasheet view while tracing is enabled, you probably expect to see a simple query such as SELECT * FROM Suppliers, or perhaps a query that includes the schema name with the table, dbo. Suppliers, and that explicitly names the three columns in the table. Instead, both the Sqlout. SQL Profiler trace show that three statements are executed. 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.

SQLPrepare is used to define a parameterized query that is then executed with SQLExecute. The question marks are placeholders for parameters. MULTI- ROW FETCH indicates that parameter values are submitted, based on values retrieved by the first query, to retrieve up to 1. A Profiler trace shows the three corresponding Transact- SQL statements that are processed on the server. In the first step, Office Access picks a . 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 1. The final step is to execute this statement, which is assigned a number on the server (6 in the example), as many times as needed, passing in 1. If there are two columns in the bookmark, 2. In this example, there are only three rows in the table, so the final bookmark value, 3, which corresponds to the last Shipper. ID in the table, is submitted eight times, because the rows are always fetched in sets of 1. The statement that fetches 1. The remaining rows are not fetched immediately unless the user performs an action such as scrolling that brings additional rows into view.

In the background during idle time, the remaining rows are gradually filled in until the recordset is complete. Wwe Raw Games Free Download For Pc 2009 Calendar here. In addition, any rows that remain visible are continually refreshed according to a configurable refresh interval that defaults to 6. Long memo and OLE object values are retrieved in separate queries only when then their columns and rows are visible. Dynasets support a continuous two- way conversation between Office Access and SQL Server for each recordset that is open. The rows that are visible are continually refreshed to show the latest data, creating extra network traffic. However, the dynamic nature of these recordsets can also reduce traffic by immediately retrieving only those rows in the vicinity of data the user is actually viewing.

If you create a form that is bound to a table containing a million rows of data (not a recommended practice) and the form shows the data from only one row at a time, only 2. If the user keeps only the first record visible, Office Access continually retrieves the first 1. If the form is left open long enough, all the rows are eventually retrieved during idle time in many separate batches, but a snapshot retrieves all the rows right away. Because they work with only a few rows at a time, dynasets minimize the duration that read locks are held on the server.