In this post, you’ll learn to work with DSUM() function with date as a criteria. It is very similar to the way you create the text criteria with the only exception being the delimiters used. In case of dates, you’ll use hash (#) as a delimiter instead of a single quote (‘ ‘) that you use in case of text values.
The date criteria enables you to extract data within a particular time period or before/after a certain date as explained in this post…
In the previous post, you have learnt how DSUM() function works as well as how to specify a text criteria. As mentioned earlier, the criteria could be a text criteria or a number or a date. Depending on the data type of the criteria, there is a slight change in how you construct the criteria part of the DSUM() function in terms of the delimiters to be used as well as the placement of the criteria value.
[Note: If you are new to DSUM() function, it is recommended that you read this post first : DSUM() function – The Art of Writing a Criteria : 1]
In this post, you are going to learn more about specifying the number criteria. Let us see how…
As you learn more in MS Access, you will find that DSUM() function or for that matter any other domain aggregate functions such as DAvg(), DCount() etc. have interesting applications in data analysis. Now, these functions are very easy to understand in terms of what they do but the only confusing part is the criteria part of the function. I have seen many people including myself getting a bit uncomfortable and making silly mistakes while constructing the criteria in this function.
In this post, you will learn what exactly does DSUM() function do and more importantly how to construct the criteria properly. So, lets begin……
In all the 4 previous posts on operators, you have seen some specific operators that can be used to perform certain specific actions. In addition to this, there are still a few additional operators provided by MS Access to assist you in your data analysis.
In this post, you’ll learn about these additional operators….
In the previous post, you have seen that if one of the value is NULL, then the output of the + operator is also NULL.
Lets consider the following example:
O = A + B
If B=NULL, then the expression “O = A + Null” will be equal to Null. But in real life, when you are adding two values and if you encounter NULL, then you want MS Access to ignore NULL value and perform the addition operation as normal i.e. you want the final output to be displayed as :
O = A + 0 i.e. O = A
Let us see how this function can be used to achieve the desired result…
Posted in Basics
Today, you’ll learn to use two very useful concatenation operators in MS Access. By definition, ‘Concatenation’ means linking of two things as in a series or chain. From MS Access standpoint, concatenation means joining/linking two strings together.
So, let’s see how you can use these operators to your benefit….
In simple English, NULL means nothing – absolutely nothing. In MS Access too, NULL means the same….no Value. NULL means absence of any value whatsoever. NULL is different from a zero Value. In fact, NULL is also different from a Zero length String (ZLS), though they appear the same visually.
The presence of NULL value indicates that maybe you have no value to add in the table, or simply the value is unknown. Furthermore, you cannot compare NULL value i.e. Comparing two NULL value will give you NULL, since by definition you have no value to compare with.