SQL Operators and Operands
In order to use a computer language, you usually give instructions to an internal program. An instruction can be formulated as a command. Examples are "give me food" or "touch your head". Another type of instruction can be formulated as a question. Examples are "what time is it?" or "Are you hungry?". The sentence or group of words that constitute an instruction is also called a statement.
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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.
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.
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.
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.
SQL allows us to combine two or more simple conditions by using the AND and OR or NOT operators. Any number of simple conditions can be present in a single SQL statement, to allow us to create complex WHERE clauses that allow us to control which rows are included in our query results.
Microsoft Access and Microsoft Visual Basic are not case-sensitive. Therefore, any word we are going to use that involves a field, its name, and new words we will introduce in this section, whether written in uppercase, lowercase or a mix, as long as it is the same word, represents the same thing. Based on this, the words TRUE, True and true, as related to Microsoft Access, represent the same word. In the same way, if the words NULL, Null, and null are used in an expression, they represent the same thing.
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?
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.
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
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.