Within my database i have 3 different tables for different members. When saving the members details i use a form to save the members all to the same table but i would like to save them to a specific table depending on their details. for example if a member has registered with their school email i would like them to be saved within the student table, if they have used a freemail email address to be saved in the freemail table etc
Would this be run as a query or sorting the one table using if statements?
You probably should not have three tables, just a field that defines the member type. You may wish to read Fundamentals of Relational Database Design.
If you really insist on having three tables, even though it is likely to cause ever more tangled scenarios, you will either have to use VBA to gather the data from an unbound form and then fill it into the appropriate table, or ask the user which table they wish to update before you start and set up the form for that table.
It depends on your development environment. You can either change the switch to an If clause at business level or you can implement it as a database procedure. It's up to you.
http://msdn.microsoft.com/en-us/library/aa933214(v=sql.80).aspx explains how to use If clause in database
Related
I am struggling with an issue in designing my Access database.
I am a caregiver, and part of my job is taking clients out into the community. I am attempting to build a catalog of outings to help the employees at our company come up with and store ideas for these. I want to store information for each of up to 5 types of events that clients can do at a location. That information includes the event type, when it runs and doesn't, and how much it'll cost, all of which would be user-selectable. (Separately in the same table, I want to include contact information and information that helps the user search for event locations, such as the ZIP code.) I have attempted to normalize the database by spreading event information across fields in the main table, linked to lookup tables. I am aware that Access has a limit of 32 relationships per table.
To help staff find event types, I am trying to set up a method for categorizing them. That requires setting up nested lookup tables, as shown in the first picture.
If I understand correctly, the additional "copies" of those lookup tables are aliases. When I save the setup for the relationships between those aliased lookup tables, close the Relationships window, and open it again, I find Access has changed them, as shown in the second picture. This happens whether I delete the lookup table information for each field in Datasheet View. I don't understand why it does this or how to fix it.
To answer your question:
In the object browser I see that you have only one table: t_OutingType. Therefore, the "tables" t_OutingType_2, t_OutingType_3 are just aliases; "pointers" to the same table (like a shortcut to a document). When you save the relationships and close the window, the relationship information is written to the metadata of the database. When you re-open the Relationships window Access re-builds the relationship diagram from the metadata, and it does not include the redundant aliases.
Additional advice:
Whenever you find yourself duplicating columns in a table, e.g., Event_1, Event_2, ... a little voice in your head should start shouting "Are you sure that's a good idea?" Imagine if you want to search the database for events that fall on a certain date. With the table layout described above you would need to ...
SELECT ... WHERE EventDate_1 = [theDate] OR EventDate_2 = [theDate] OR EventDate_3 = [theDate] ...
It's almost always better to split the Event information into a separate child table and maintain an association table between the child table and its parent.
I hope someone can help me with this:
I have a simple query combining a list of names and basic details with another table containing more specific information. Some names will necessarily appear more than once and arbitrary distinctions like "John Smith 1" and "John Smith 2" are not an option, so I have been using an autonumber to keep the records distinct.
The problem is that my query is creating two records for each name that appears more than once. For example, there are two clients named 'Sophoan', each with a different id number, and the query has picked up each one twice resulting in four records (in total there are 122 records when there should only be 102). 'Unique values' is set to 'yes'.
I've researched as much as I can and am completely stuck. I've tried to tinker with sql but it always comes back with errors, I presume because there are too many fields in the query.
What am I missing? Or is a query the wrong approach and I need to find another way to combine my tables?
Project in detail: I'm building a database for a charity which has two main activities: social work and training. The database is to record their client information and the results of their interactions with clients (issues they asked for help with, results of training workshops etc.). Some clients will cross over between activities which the organisation wants to track, hence all registered clients go into one list and individual tables spin of that to collect data for each specific activity the client takes part in. This query is supposed to be my solution for combining these tables for data entry by the user.
At present I have the following tables:
AllList (master list of client names and basic contact info; 'Social Work Register' and 'Participant Register' join to this table by
'Name')
Social Work Register (list of social work clients with full details
of each case)
Social Work Follow-up Table (used when staff call social work clients
to see how their issue is progressing; the register has too many
columns to hold this as well; joined to Register by 'Client Name')
Participants Register (list of clients for training and details of
which workshops they were attended and why they were absent if they
missed a session)
Individual workshop tables x14 (each workshop includes a test and
these tables records the clients answers and their score for each
individual test; there will be more than 20 of these when the
database is finished; all joined to the 'Participants Register' by
'Participant Name')
Queries:
Participant Overview Query (links the attendance data from the 'Register' with the grading data from each Workshop to present a read-only
overview; this one seems to work perfectly)
Social Work Query (non-functional; intended to link the 'Client
Register' to the 'AllList' for data entry so that when a new client
is registered it creates a new record in both tables, with the
records matched together)
Participant Query (not yet attempted; as above, intended to link the
'Participant Register' to the 'AllList' for data entry)
BUT I realised that queries can't be used for data entry, so this approach seems to be a dead end. I have had some success with using subforms for data entry but I'm not sure if it's the best way.
So, what I'm basically hoping to achieve is a way to input the same data to two tables simultaneously (for new records) and have the resulting records matched together (for new entries to existing records). But it needs to be possible for the same name to appear more than once as a unique record (e.g. three individuals named John Smith).
[N.B. There are more tables that store secondary information but aren't relevant to the issue as they are not and will not be linked to any other tables.]
I realised that queries can't be used for data entry
Actually, non-complex queries are usually editable as long as the table whose data you want to edit remains 'at the core' of the query. Access applies a number of factors to determine if a query is editable or not.
Most of the time, it's fairly easy to figure out why a query has become non-editable.
Ask yourself the question: if I edit that data, how will Access ensure that exactly that data will be updated, without ambiguity?
If your tables have defined primary keys and these are part of your query, and if there are no grouping, calculated fields (fields that use some function to change or test the value of that field), or complex joins, then the query should remain editable.
You can read more about that here:
How to troubleshoot errors that may occur when you update data in Access queries and in Access forms
Dealing with Non-Updateable Microsoft Access Queries and the Use of Temporary Tables.
So, what I'm basically hoping to achieve is a way to input the same data to two tables simultaneously (for new records) and have the resulting records matched together (for new entries to existing records). But it needs to be possible for the same name to appear more than once as a unique record (e.g. three individuals named John Smith).
This remark actually proves that you have design issues in your database.
A basic tenet of Database Design is to remove redundancy as much as possible. One of the reasons is actually to avoid having to update the same data in multiple places.
Another remark: you are using the Client's name as a Natural Key. Frankly, it is not a very good idea. Generally, you want to make sure that what constitutes a Primary key for a table is reliably unique over time.
Using people's names is generally the wrong choice because:
people change name, for instance in many cultures, women change their family name after they get married.
There could also have been a typo when entering the name and now it can be hard to correct it if that data is used as a Foreign Key all in different tables.
as your database grows, you are likely to end up with some people having the same name, creating conflicts, or forcing the user to make changes to that name so it doesn't create a duplicate.
The best way to enforce uniqueness of records in a table is to use the default AutoNumber ID field proposed by Access when you create a new table. This is called a Surrogate key.
It's not mean to be edited, changed or even displayed to the user. It's sole purpose is to allow the primary key of a table to be unique and non-changing over time, so it can reliably be used as a way to reference a record from one table to another (if a table needs to refer to a particular record, it will contain a field that will hold that ID. That field is called a Foreign Key).
The names you have for your tables are not precise enough: think of each table as an Entity holding related data.
The fact that you have a table called AllList means that its purpose isn't that well-thought of; it sounds like a catch-all rather than a carefully crafted entity.
Instead, if this is your list of clients, then simply call it Client. Each record of that table holds the information for a single client (whether to use plural or singular is up to you, just stick to your choice though, being consistent is hugely important).
Instead of using the client's name as a key, create an ID field, an Autonumber, and set it as Primary Key.
Let's also rename the "Social Work Register", which holds the Client's cases, simply as ClientCase. That relationship seems clear from your description of the table but it's not clear in the table name itself (by the way, I know Access allows spaces in table and field names, but it's a really bad idea to use them if you care at least a little bit about the future of your work).
In that, create a ClientID Number field (a Foreign Key) that will hold the related Client's ID in the ClientCase table.
You don't talk about the relationship between a Client and its Cases. This is another area where you must be clear: how many cases can a single Client have?
At most 1 Case ? (0 or 1 Case)
exactly 1 Case?
at least one Case? (1 or more Cases)
any number of Cases? (0 or more Cases)
Knowing this is important for selecting the right type of JOIN in your queries. It's a crucial part of the design assumptions when building your database.
For instance, in the most general case, assuming that a Client can have 0 or more cases, you could have a report that displays the Client's Name and the number of cases related to them like this:
SELECT Client.Name,
Count(ClientCase.ID) AS CountOfCases
FROM Client
LEFT JOIN ClientCase
ON Client.ID = ClienCase.ClientID
GROUP BY Client.Name
You've described your basic design a bit more, but that's not enough. Show us the actual table structures and the SQL of the queries you tried. From the description you give, it's hard to really understand the actual details of the design and to tell you why it fails and how to make it work.
As a general question which would really help me "connect the dots" with my studies.
I am currently doing exercises working with DAO and Learning how to add tables automatically. Although i have been working with databases for many years, i question, what type of scenerarios would it be vantagious to use this function. When is it necessary to add tables to a database in an automatic way? Up until now, in all my experiences the tables i need have Always been defined from the beginning and I cant think of a situation where I could of benefited from using this function. For example, i use frequently delete queries to help me clear tables and re-populate them, but when would it be necessary to actually "create" a new table"?
Yes, I have seen a scenario where new tables were created 'on the fly' (either via SQL create, or just DAO). With a shared database on a server, the application called for importing Excel data that a particular user was responsible for, so a table was created on the fly. Multiple users, changes in staff, need to keep data independent, etc. we could create their own table (name based on userid) that they had interfaces to do whatever they wanted with their own data. Not a typical scenario, but worked well for this application.
Which one would be better (performance wise and maintenance), a database which creates table dynamically or just adding rows dynamically?
Suppose I am building a project in which I let users to register. Say I have a table which store only basic personal infos, like name, dob, Date of joining, address, phone, etc. Say 10 columns.
Now is the tricky part.
Scene 1: Creating multiple tables
When a user complete registration, a message table is created. So each table is created for each users. The rows of each message table varies for each user.
In the same way there is a cart table for each user like the message table.
For this scene 1, 2 tables are created with every registration.
Scene 2: Adding Rows
The scenario is same here as well, but in this case I have 2 tables for message and cart. Rows are added only when there is an activity.
Note:
You must assume that the number of users is more than 2000 and expect 50+ users to be active all the time. Which means the message and cart tables are always busy for both the cases. Like there is always a query for update, add, delete, insert, select etc. simultaneously.
Also which scene will consume more disk space.
While writing this, it make me wonder what technique would Facebook and others use. If they use the Scene 2 style (all users (billions) use the same big long message table)... Just wondering
Databases has some basic rules defined for Database Design called
"Database Normalization", These basic rules allow us eliminating
redundant data.
1st Normal Form
Store One piece of information in only One Column, A column should store only One piece of information.
2ns Normal Form
A Table should have only the columns that are related to each other. All the related columns should be in One table.
Now if you look at your advised design, A Separate Table for each USER
will split SAME information/Columns about all the user in 1000's of
tables. Which violates the 2nd Normal Form.
You need to Create One Table and put all the related Columns in that
one table for all the users. and you can make use of normal t-sql to
query your data but if you have a table for each user my guess is your
every query that you execute from your application will be built
dynamically and for every query you will be using dynamic sql. which
is one of the Sql Devils and you want to avoid using it whenever
possible.
My suggestion would be read more about Database Design. Once you have
some basic understanding of database design. Draw it on a piece of
paper and see if it provides you everything that your business
requires / expects from this application , Spend sometime on it now it
will save you a lot of pain later.
I'm building an stock exchange simulation game. I have a table called 'Market_data' and in the game players simulate being in particular dates and are allowed to use SQL queries to retrieve the historical data and plan their course of action. My difficulty is that I need to limit the rows they can access based on the current date they are playing on so they cant see rows with a date greater than the current date.
Eg: An user is running the game and is currently in the year 2010, if he does a simple select like "SELECT * FROM market_data" I don't want him to see rows with Date > 'x-x-2010'
The only soution that I know of is to parse the user's SQL and add WHERE clauses to remove newer dates but it seems time consuming and prone to errors and I wasn't sure whether there were better alternatives. Any ideas on how to do this right will be thanked.
Solution is SQL Views, Views are used for several different reasons:
*1.*To hide data complexity. Instead of forcing your users to learn the T-SQL JOIN syntax you might wish to provide a view that runs a commonly requested SQL statement.
*2.*To protect the data. If you have a table containing sensitive data in certain columns, you might wish to hide those columns from certain groups of users. For instance, customer names, addresses and their social security numbers might all be stored in the same table; however, for lower level employees like shipping clerks, you can create a view that only displays customer name and address. You can grant permissions to a view without allowing users to query the underlying tables. There are a couple of ways you might want to secure your data:
a.Create a view to allow reading of only certain columns from a table. A common example of this would be the salary column in the employee table. You might not want all personnel to be able to read manager's or each other's salary. This is referred to as partitioning a table vertically and is accomplished by specifying only the appropriate columns in the CREATE VIEW statement.
b.Create a view to allow reading only certain rows from a table. For instance, you might have a view for department managers. This way, each manager can provide raises only to the employees of his or her department. This is referred to as horizontal partitioning and is accomplished by providing a WHERE clause in the SELECT statement that creates a view.
*3.*Enforcing some simple business rules. For example, if you wish to generate a list of customers that need to receive the fall catalog, you can create a view of customers that have previously bought your shirts during the fall.
*4.*Data exports with BCP. If you are using BCP to export your SQL Server data into text files, you can format the data through views since BCP's formatting ability is quite limited.
*5.*Customizing data. If you wish to display some computed values or column names formatted differently than the base table columns, you can do so by creating views.
reference taken from http://sqlserverpedia.com.
1)You can use mysql proxy http://dev.mysql.com/downloads/mysql-proxy/ with custom rules restricting access.
2)You can use stored procedures/functions
3)You can use views
The basic way would be :
-> Prevent that user (or group) from accessing the base table.
-> Define a view on top of that table that shows only the rows these users are supposed to see.
-> Give those users SELECT permission on the view.
-> And you can also use SQL Encryption,Decryption and Hashing concept.
Encryption & Decryption examples can be found here:
http://msdn.microsoft.com/en-us/library/ms179331.aspx
Hashing example can be found here:
http://msdn.microsoft.com/en-us/library/ms174415.aspx