4 Session4 Queries

7/30/2019 4 Session4 Queries

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access session 4

Using Queries to Select Data


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Database Operation in Table Datasheet view Retrieve, sort and group data

Limit results

Evaluate expressions


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Table Datasheet view Operations(Sort and Filter)

how to. Records menu

Table Datasheet toolbar

Filter by Selection Excel concept ofAutoFilter

Filter by Form Excel concept of Custom

Filter


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Comparison and Logical Operators

Comparison Logical= Equals

OrMeets any onecondition> Greater than

>= Greater than or equal And Meets allconditions< Less Than


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Query Preliminaries

Queries are used to sort, filter, add, delete,and modify data in MS Access databases

use queries to request data for forms,

reports, and controls when an object relieson specific data rather than on all the datain the underlying table.


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Query Types 1/2

Select: retrieve data that meets specificconditions, group records for viewingsummary data, and display calculations

performed on data fieldsAction: modify existing data in some way,

used to delete, update, and append data orto create a new table.


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Query Types 2/2

Parameter: prompt you for criteria beforerunning the actual query

Crosstab: summarize data and then groupthe summarized values into categories

SQL: include union, pass-through and data-definition queries, require specific SQLcommands, that you must compose in SQL

view


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the query environment

query Design view: identify the tables and queriesthat you want to include in your query. and create& view queries

field list: upper part window displays a field list for each

table or query design grid: lower part window, define the querys fields

and accept expressions as criteria for limiting the resultsof the query


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SQL view: translated query design view intoJet Structured Query Language.


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Common SQL keywords

AS: creates a clause that specifies an expressionor value and the field name associated with it

DISTINCTROW: exclude duplicate records from

the query FROM: Create a clause specifying the table or

query from which fields are taken for the query

ORDER BY: Crates a clause containing a list offields to be included in the query


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SELECT: creates a clause containing a listof fields to be includes in the query

UNION: Combines two sets of records into

a single set WHERE: Creates a clause with a condition

(or set of conditions) for filtering query

records.


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The Simple Query wizard Summarizing Data using the Wizard

Retrieving Data using the Design view

1. click new, then add fields from the Show tablewindow

2. execute the query using the Run button from

the Query Design toolbar


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5 methods for adding fields to thedesign grid

double-click the field in the field list drag the field to a column

double-click or drag the * in the field list

field drop-down list

type the field name in a columns Field cell


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other design grid components

Sorting Records: using the Sort cell Computing totals for group records: using

Group by Drop-down list (view menu,

totals) Limiting Data: using the Criteria or Or cell


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Crosstab

Crosstab query is a query that groupssummarized data by categories, a morecompact way to group and summaries record

Crosstab vs PivotTable both summarize data using aggregate functions

PivotTables are more powerful because they candisplay the detailed data behind those subtotals and

grand totals without affecting the groups


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Crosstab vs PivotTable (cont.) column headings: PivotTables (multiple) while

Crosstab (one)

PivotTables also include crossfoot totals,Crosstab none

PivotTables: quicker to produce and moreflexible that crosstab queries


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To sum it up

datasheet sorting & filtering vs. queries Both can be manipulated using the design grid

area

Queries: saved objects Manipulate the query design view, design

grid area

Documents

4 Session4 Queries