003.query

Queries That Select Records
(Chapter 6 – 7)

Query Basics
 A Microsoft Access query is a question about
the information stored in Access tables.
 Your query can be a simple question about data
in a single table, or it can be a more complex
question about information stored in several
tables.
 After run query, Microsoft Access returns only
the information you requested.

Creating Queries in Design View
 The best starting point for query creation is the
Design view.
− ChooseCreate  Queries  Query Design.
− Select the table that has the data you want,
and then click Add  Click Close.

− Select the fields you want to include in query.
− Arrange the fields from left to right in the
order to appear in the query results.
− If you want to hide one or more columns, then
clear the Show checkbox for those columns.

− Choosea sort order.
− Set your filtering criteria by place the
expression into the Criteria box for the
appropriate field.

− Choose Query Tools Design  Results 
Run. Save the query.

Getting the top records
 Use the Top Values box on the Design View
toolbar to see the top records produced by the
query.
− Open query in Design view.
− Sort table so that the records you’re most
interested in are at the top.
− In the Query Tools  Design
− Query Setup  In return box,
−  choose a different option

Creating Queries by Wizard
 Create a simple Query by using wizard.
 The Query wizard works by asking you a series
of questions.
− ChooseCreate  Queries  Query Wizard.

− Choose a query type. The Query wizard
includes a few common kinds of queries.
 Simple Query Wizard.
 Crosstab Query Wizard.
 Find Duplicates Query Wizard.
 Find Unmatched Query Wizard
− OK.
− In the Tables/Queries box, choose the table
that has the data you want.

− Add the fields you want to see in the query
results
− Click Next. Enter query name  Click Finish.

Understanding the SQL View
 Behind the scenes, every query is actually a text
command written in a specialized language
called SQL (Structured Query Language).
 To take a look at the SQL command for a query,
right-click the tab title, and then choose SQL
view.
 Example:
1 SELECT Products.ID, Products.ProductName, Products.Price
2 FROM Products
3 WHERE (((Products.Price)>50))
4 ORDER BY Products.Price;

Understanding the SQL View
 Every query has common ingredients (thành
phần), represented by:
− SELECT: list of fields appear in the query
results.
− FROM: indicates the table (or tables) that
you’re searching.
− WHERE: indicates the start of your filter
conditions.
− ORDER BY: define the sorting order.

Queries and Related Tables
 A join line connects tables in the query design.
The join line connects the primary key in one
table to the foreign key in another table.
 By default, an Access query returns only
records where data exists on both sides of a
relationship.
 To see records that are not matched on the
other side of the join. You must modify the
default query join.

Queries and Related Tables
 Can create joins between tables in these three
ways:
− By creating relationships between the tables
when you design the database.
− By selecting two tables for the query that have
a field in common that has the same name
− By modifying the default join behavior

Calculated Fields
 To create a calculated field, you need to supply
two details:
Field Name : Expression

 Example: define the PriceWithTax calculated
field:
PriceWithTax: [Price] * 1.10
Field Expressio
Name n

Simple Math with Numeric Fields
 Simple Math with Numeric Fields
Operator Name Example Result
+ Addition 1+1 2
– Subtraction 1–1 0
* Multiplication 2*2 4
^ Exponentiation 2^3 8
/ Division 5/2 2.5
Integer division 52 2
Mod Modulus 5 Mod 2 1

Expressions with Text
 To join text, use the ampersand (&) operator.
 For example:
− Create a FullName field from the FirstName
and LastName fields:
FullName: [FirstName] & “ “ & [LastName]
− To “The price is” to appear before each price
value, use this calculated field:
Price: "The price is: " & [Price]

Query Functions
 A function is a built-in algorithm that takes
some data that you supply, performs a
calculation, and then returns a result.
 Functions is used in:
− Calculated fields. To add information to your
query results.
− Filter conditions. To determine what records
you see in a query.
− Visual Basic code.

Using a Function
 To use a function:
− Enter the function name, followed by
parentheses.
− Inside the parentheses, put all the information
the function needs in order to perform its
calculations.
Example:
SalePrice: Round([Price] * 0.95, 2)

The Expression Builder
 To quickly find the functions you want, Access
provides a tool called the Expression Builder.
 To launch the Expression Builder:
− Open a query in Design view.
− Right-click the box where you want to insert
your expression, and then choose Build.
− Add or edit the expression.
− Click OK.

The Expression Builder
 To find a function:
− Expand the Functions item, and choose Built-
In Functions.
− Next, choose a function category in the
Expression Categories list.
− The Expression Values list will show all the
functions in that category.
− Double click on functions name to insert it
into your expression.

Formatting Numbers
 Format(): mathematical function that
transforms numbers into text.
 Example:
SalePrice: [Price] * 0.95
− Use the Format() function to apply a currency
format:
SalePrice: Format([Price] / 0.95, "Currency")

Formatting Numbers
Format Description Example
Displays a number with two decimal places,
Currency $1,433.20
thousand separators, and the currency sign.
Fixed Displays a number with two decimal places. 1433.20
Displays a number with two decimal places
Standard and the thousands separator. 1,433.20

Displays a percent value. Displays 2 digits to
Percent 143320.00%
the right of the decimal place.
Displays a number in scientific notation, with
Scientific two decimal places. 1.43E+03

Displays No if the number is 0 and Yes if the
Yes/No number is anything else. Yes

Functions
 More Mathematical Functions (Page 230)
 Text Functions (Page 232)
 Date Functions (Page 234)

Summarizing Data
 Total function is used to group the records to
arrive at totals and subtotals. That way, you can
review large quantities of information much
more easily.
 Example:
− Counting all the students in each class.
− Counting the number of orders placed by each
customer.
− Totaling the amount of money spent on a
single product.

Summarizing Data
 These operations are used to summarize data:
− Count
− Sum
− Average
− Max
− Min

Summarizing Data
 Create a totals query:
− Create a new query by choosing Create➝
Queries ➝ Query Design.
− Add the tables you want to use from the Show
Table dialog box, and then click Close.
− Add the fields you want to use.
− Choose Query Tools Design  Show/Hide
Totals.

Summarizing Data
 For eachfield, choose an option from the Total
box. This option determines whether the field is
used in a calculation or used for grouping.
 Every field must belong to one of these
categories:
− It’s used in a summary calculation (like
averaging, counting, …).
− It’s used for grouping.
− It’s used for filtering.

Summarizing Data
Choice in the
Description
Total box
Subgroups records based on the values in this
Group By
field.
Sum Adds together the values in this field.
Avg Averages the values in this field.
Min Retains the smallest value in this field.
Max Retains the largest value in this field.
Counts the number of records (no matter
Count
which field you use).
First Retains the first value in this field.
Last Retains the last value in this field.

Summarizing Data
 Example: Calculate Total for every Order

Query Parameters
 Query parameters let you create flexible
queries by enter one pieces of information.
 Every time you run the query, Access prompts
you to supply the missing values. These missing
values are the query parameters.
 Usually, query parameters are used in filter
conditions.
 When run the query, you fill in the value you
want to use at that particular moment.

Query Parameters
 To create a query that uses parameters:
− Create a new query by choosing Create 
Queries  Query Design.
− From the Show Table dialog box, add the
tables you want to use.
− Choose Query Tools Design Show/Hide 
Parameters. The Query Parameters dialog box
appears.
− Choose a name and data type for parameter.
− Click OK to close the Query Parameters dialog
box.

Crosstab Queries
 A crosstab query is a powerful summary tool
that examines huge amounts of data and uses it
to calculate information like subtotals and
averages.
 Crosstab queries use two key ingredients:
grouping and summary functions.
− The grouping is used to organize the rows into
small sets.
− The summary function is used to calculate a
single piece of information for each group.

Crosstab Queries
 Creating Crosstab Queries: have two ways to
create a crosstab query:
− The Crosstab Query Wizard provides an
automated way to create a Crosstab query.
The wizard works only with one table or
query.
− Build Crosstab Query by hand.

Crosstab Queries
 Creating a Crosstab Query with the Wizard
− Display the Create tab on the Ribbon.
− Click the Query Wizard button in the Macros
& Code group on the Ribbon.
− The New Query dialog box opens.
− Select the Crosstab Query Wizard option and
then click OK.
− Select the table or query that contains all the
fields you need for your Crosstab query, and
then click Next.

Crosstab Queries
− Select the field(s) whose values you want to
use as row headings  click Next.
− Select the field(s) whose values you want to
use as column headings  click Next.
− If select a date field as the column headings,
Choose how to group dates from the list
Next.
− Choose the field whose values grouped by the
row and column headings that are selected.

Crosstab Queries
− Select a grouping method from the Functions
list.
− Choose whether to include row sums by
selecting the check box on the same page as
the function choices, and then click Next.
− Name the query and then click Finish to see
the Crosstab query.

Crosstab Queries
 Creating a Crosstab query in Design view: A
simple Crosstab query has three fields:
− One used for row headings
− One used for column headings.
− The Value field, which contains the data that
you want to appear in the cells of the table.
Tell Access how to summarize your data in the
Crosstab query by choosing from these
choices: Sum, Avg, Min, Max, Count, StDev, Var,
First, or Last.

Crosstab Queries
− Choose Create ➝ Queries ➝ Query Design.
− Add the table or query you want to use in
crosstab query.
− Query Tools  Design Query Type 
Crosstab.
− Choose the fields use for row labels and in the
Crosstab row, choose the Row Heading.
− Choose the fields use for Column labels and in
the Crosstab row, choose the Column Heading.

Crosstab Queries
− Select the field containing the values that you
want aggregated, in the Crosstab row, choose
the Value option.
− Set the Total row:
 Group By option for column heading and
row heading.
 Choose summarize the data for the Value
field column.

003.query

More Related Content

What's hot (20)

Similar to 003.query (20)

More from Học Huỳnh Bá (20)

003.query