logical operators in a query
Logical Operators in Access SQL
Originally, logical operators were a concept from algebra used to exclude and include number sets. They are, very simply, NOT, AND, and OR. Sometimes this set is expanded to combinations of the operators, but at core it's only these three. The logical operators are often referred to as the Boolean operators.
Table of operators
An operator is a sign or symbol that specifies the type of calculation to perform within an expression. There are mathematical, comparison, logical, and reference operators. Access supports a variety of operators, including arithmetic operators such as +, -, multiply (*), and divide (/), in addition to comparison operators for comparing values, text operators for concatenating text, and logical operators for determining true or false values. This article provides details about using these operators.
Query Criteria In Access 2010 Through Logical Operators
As the name implies, Query pulls out specific data from table fields included in database, thus, setting specific criterion in query helps you to filter down the table field data according to your needs. Through simple logical operators in Query Criteria you can set a criteria by using simple AND/OR operators, which lets you to confine the results of a query based upon the query criteria to check which table field data is to be included.
Exploring Data Analysis
To further enhance your filtering capabilities, you can use Boolean algebra combined with the operators we have used so far. Besides the logical operators we know already, Boolean algebra adds extra operators used to concatenate expression.
Database Operators and Operands
The fields we have been using allow the user to enter, view, or change data of a database. Because there is so many types of values a user can be ask to deal with, the values in the fields are categorized by types. Learn: Overview of Operators and Operands, Constants, Operators, Logical Operators.
Database Conditional Values
1) Boolean Values
2) Logical Constants
3) Logical Operations
4) Logical Functions
5) Value Checking Functions
6) Logical Comparisons
The above mentioned topics are covered in this Access 2007 tutorial.
Data analysis: Querying a Database
To query the records of a database, you can use Boolean algebra combined with some operators. Boolean Algebra works on logical statements. A statement is a sentence that acknowledges a fact or a possibility. That fact is eventually evaluated as being true or false.
Techniques of Data Analysis
Data analysis consists of examining the records of a table, an already existing query, or a form, to isolate records that respond to one or more criteria. To assist you with this, Microsoft Access provides all the (visual) tools you need. These include filtering by form and logical junction operators.
Database Conditional Values
A value is referred to as Boolean when it is either true or false. In other words, the value only be one or the other, never both, and not any other value. To support Boolean values, Microsoft Access provides a data type named Boolean.
Learning Objective: Boolean Values, Logical Constants, Logical Operations, Logical Functions, Value Checking Functions, Logical Comparisons.
Details on Creating Queries
In this tutorial you will learn about creating queries. Topics: Details on Column Selection, Introduction to Logical Operators and Pattern Operator: LIKE.
Tables and Relationships
Situation: I'm creating a database to keep track of earth moving activities. There are multiple operators (people operating the earth moving equipment). There are also multiple pieces of equipment.
In any given shift, multiple operators may use one piece of equipment. Similarly, one operator may use multiple pieces of equipment.
I'm thinking that I should create a table for all the operators, and then a table for all the equipment and establish a 'many to many' relationship between the primary key of the equipment(the equipments ID number) and the primary key of the operators table (the operators employee number).
Is this a valid structure, and is it one that can be implemented in Access?
One of the goals of computer programming is telling the computer what to do when something occurs, and how to do it. This is performed by setting conditions, examining them and stating what decisions the computer should make. To perform the necessary conditions, you have two main options: Microsoft Access or Microsoft Visual Basic. Microsoft Access is equipped with a series of operators and functions destined to perform various operations. To use a condition in Microsoft Access, if you know the structure of the conditional statement, you can write it after typing an assignment operator. Because most conditions in Microsoft Access are in the form of functions, we will study them later on. For now, we will learn how to write conditions in the Microsoft Visual Basic language.
Topics: Topics: Logical Operators, The If...Then Statement, The If...Then...Else Statement, The If...Then...ElseIf Statement, The Select Case Statement, Looping and Counting.
Nest a query inside another query or in an expression by using a subquery
Sometimes you may want to use the results of a query as a field in another query, or as a criterion for a query field. For example, suppose that you want to see the interval between orders for each of your products. To create a query that shows this interval, you need to compare each order date to other order dates for that product. Comparing these order dates also requires a query. You can nest this query inside of your main query by using a subquery (subquery: An SQL SELECT statement that is inside another select or action query.).
You can write a subquery in an expression (expression: Any combination of mathematical or logical operators, constants, functions, and names of fields, controls, and properties that evaluates to a single value. Expressions can perform calculations, manipulate characters, or test data.) or in a Structured Query Language (SQL) statement in SQL view (SQL view: A window that displays the SQL statement for the current query or that is used to create an SQL-specific query (union, pass-through, or data definition). When you create a query in Design view, Access constructs the SQL equivalent in SQL view.).
Creating a Validation Rule in an Access Table
The validation rules use the same logical expressions that can be found typically in criteria of a query and must return a logical value of either TRUE or FALSE in order to accept or reject the value and trigger an exception (validation text property). This simple property is easier to apply than attaching a macro or VBA code to an event which means learning VBA programming!
List box with operators
I need to create a list box with operators and I'm having difficulty figuring out how to tell access that greater than = > and less than = < and or = or and so on
Microsoft Access Query Operators
Queries are a very important feature of Microsoft Access that can tell you information about the data stored in the Access tables. Queries make it easier to search the data from different fields. Therefore, using queries to achieve the results you are looking for is quite a useful tool. However, when you have large amounts of information, you will need more advanced techniques such as Boolean Operators to make sense of the queries you have inputted.
Introduction to Expressions
An expression is a combination of data fields, operators, values, and/or procedures destined to produce a new value. There are various types of expressions you will be using in your applications. When creating an expression, you would ask the database engine to supply data of a specific field following your recommendation. Data you specify is usually not provided by a field on a table. Instead, you can create a field that is a combination of fields from a table, a form, a query, or a report. The data of the expression can also be the result of a combination of dependent fields or values external to any table, form, query, or report.
This topic covers the following: Algebraic Expressions, VBA and Expressions, Procedures and Functions, The Expression Builder, Introduction to Built-In Functions, Logical Functions, Field Emptiness, Nullity Checking, Numerical Checking and Non-Zero Checking.
Examples of expressions
This article provides examples of expressions. An expression is a combination of mathematical or logical operators, constants, functions, table fields, controls, and properties that evaluates to a single value. You can use expressions to calculate values, validate data, and set a default value for a field or control.
In this article
* Understand expressions
* Examples of expressions used in forms and reports
* Examples of expressions used in queries and filters
* Examples of default value expressions
* Examples of field validation rule expressions
* Examples of macro condition expressions
Conjunction and Disjunction in Data Analysis
Consider a database that contains a list of students with various pieces of information. Imagine that our main goal is to make sure that we have a number we can use to contact somebody for the student. In this case, either the home phone number or the emergency number would be fine.
TOC: Logical Disjunction, Logical Conjunction.
Introduction to DAO, ADO, ADOX, and SQL
Microsoft Access ships with a language named Visual Basic For Applications, or VBA. This allows you to complement MS Access with code that can perform complex operations. This language is used throughout the Microsoft Visual Office family of applications, including Microsoft Excel, Work, PowerPoint, Visio, etc. This language is also used by applications published by companies other than Microsoft. An example is Autodesk that publishes AutoCAD. To customize the VBA language for our database environment, Microsoft Access includes a library called Microsoft Access Object Library.
Topics Microsoft Access Object Library and VBA, Microsoft Data Access Objects, Database Creation With DAO, The Structured Query Language, Introduction to SQL Operators, Unary Operators, Binary Operators, Microsoft ActiveX Data Objects, ADOX Fundamentals, The Data Source of an Application and The Connection to a Database.