Query in Microsoft Access

Lesson plan

• Expression in Microsoft Access

• Create a query

Expression in Microsoft Access

• An expression is a combination of – data fields, operators, values, and/or

functions

• Data fields: column names/attribute names that are put inside[ ] such as [Price]

• Values: number (Int, Double), date…

• Functions: Math (e.g abs), String(len)

Expression in Microsoft Access

Algebraic/Arithmetic Expressions :

Contains arithmetic operators:

+ add

- Subtract

* Multiplication

/ Division

Mod: modulo

^ raise to a power

\ divide one integer by another

Expression in Microsoft Access

Algebraic/Arithmetic Expressions :

Example:

Expression in Microsoft Access

Boolean Expressions :

Contains comparison/relational and/or boolean operators:

Comparison operators:

< less than

<= less than or equal to

= equal to

<> Not equal to

> Greater

>= Greater than or equal to

Expression in Microsoft Access

Example:

Expression in Microsoft Access

Boolean Expressions :

Boolean operators:

and logical AND

or logical OR

NOT Logical NOT

Xor Exclusive OR

Expression in Microsoft Access

Example

Expression in Microsoft Access

Other operators:

Is: Example: Is nullIn: determine whether a string value is a

member of a list of valuesLike: determine whether a string value

begins with one or more characters, use with * or ?

E.g [firstname] like “Jon*”Between: determine whether a numeric or

date value lies within a specific range of values

E.g between 1 and 7

Expression in Microsoft Access

Example

Expression in Microsoft Access

Functions:

Math

String (Text manipulation)

Financial

Data & time

Expression in Microsoft Access

Query in Microsoft AccessIs used to select a group of records that meet

the criteria a user specifies (VIEW)

Combine information from different tables and provide a unified view of related items

Query in Microsoft AccessExample: Create a query using Query design

window

Query -> Query by Design View

Query in Microsoft AccessSelect tables being included in a query

Select fields being included in a query

Specify the criteria

Query in Microsoft AccessSorting the display

Query in Microsoft AccessPreventing updates to the query result set

Why needed?: preventing users from updating the results of the queries

Query in Microsoft AccessTypes of queries

• Select: as shown in previous slides• Action: such as create a table, delete,

update• Parameter: repeatedly use a query and

make only a simple changes to its criteria• Crosstab: summarize data from one or

more tables in the form of spreadsheet

Action queriesCreate Query by Design View -> Right click mouse

Action queries

Parameter queries

Parameter queries

Queries – Practice

• Please try the first 11 queries in project 1 part 3.

• If done, please try queries from 12-14

Crosstab queries

Join tables

Create Crosstable queries

Join tables

– How to join multiple tables• Identify relationships among tables • Four types of joins:

– Equi-joins– Outer joins– Self-joins– Theta joins

Equi-joins (inner joins)

– Display all the records in one table that have corresponding records in another table

Example:

Equi-joins (inner joins)

Equi-joins (inner joins)

Equi-joins (inner joins)

….

Designing Nested Queries

Establish the relationship between a query and a table

Designing Nested Queries

Establish the relationship between a query and a table

Designing Nested Queries

Designing Nested Queries

Designing Nested Queries

Outer joins

Display records in one member of the join, regardless of whether corresponding records exist on the other side of the join

Outer joins

Self joins

Display rows for which values of two columns in the same table are equal

Theta joins

Relate data by using NOT equal comparison rather than equal comparison

Theta joins

Relate data by using NOT equal comparison rather than equal comparison

Practice

Try queries 10-20 in the project part 3