Like a house, a good database is built with forethought, and with proper care and attention given to the needs of the data that will inhabit it; it cannot be tossed together in some sort of reverse implosion. That’s when the “hacking” starts, with the veiled promise to go back and fix things later, something that happens very rarely indeed. Names, while a personal choice, are the first and most important line of documentation for your application. By carefully naming your objects, columns, and so on, you can make it clear to anyone what it is that your database is modeling.

Your goal should be to provide enough information that when you turn the database over to a support programmer, they can figure out your minor bugs and fix them (yes, we all make bugs in our code!

In a database, the process of normalization, as a means of breaking down and isolating data, takes every table to the point where one row represents one thing.

You can still have one editor for all rows, as most domain tables will likely have the same base structure/usage. The word surrogate means “something that substitutes for” and in this case, a surrogate key should be the stand-in for a natural key. In summary: as a rule, each of your tables should have a natural key that means something to the user, and can uniquely identify each row in your table. Taken as a whole, this rule smacks of being rather messy, not very well controlled, and subject to frequent change. In this manner the impact to the user interfaces could be quite small, while the code of stored procedures might change greatly. Server works best when you minimize the unknowns so it can produce the best plan possible. As database professionals know, the first thing to get blamed when a business system is running slow is the database. But let’s face it; testing is the first thing to go in a project plan when time slips a bit.

When that car subsequently “failed” on the first drive along a freeway, or during the first drive through rain or snow, then the driver would have every right to be very upset.

Once the major bugs are squashed, the fringe cases (which are pretty rare cases, like a user entering a negative amount for hours worked) start to raise their ugly heads. If everyone insisted on a strict testing plan as an integral and immutable part of the database development process, then maybe someday the database won’t be the first thing to be fingered when there is a system slowdown. If columns in a table have different data types, how are you storing all the values in the same table?

She was especially good at giving each space the final accessory touch to bring it all together.

Database design mistakes

Store anything that will be later used by your application in the database, the other stuff in log files. Same with your concern about the load on the server – there are much better ways of dealing with that than resorting to keeping data in flat files. Oldstyle figures look nice in sentences, where they better match the size and spacing of lower-case letters; lining figures are more uniform, and reinforce the grid-like structure of the table. While the difference may not seem great on the scale of one or two lines, using tabular figures makes scanning large tables significantly easier and less error-prone. How would you align two columns with numerical and textual data when numerical is on a left side of textual data?

This is sometimes imposed using triggers or maybe just application logic, but it’s important in practice because it gives you “proof” that nothing’s been tampered with in a way which is difficult to detect.

Database tables data

ten common database design mistakes

The design should be so simple or universally understood that the learning curve for new developers is minimized. We also log old and new values and the column they are from as well as the primary key of the table being audited in an audit detail table. At bare minimum you should move audit data to separate tables in the different filegroups. So when user select 10 transaction table for logging (from front end) i need to log all transactions (insert / update / delete) in the history table. But any better way for this like find only changed column or any other design something like this.

This list simply reflects the database design mistakes that are currently on my mind, or in some cases, constantly on my mind. Let me ask you: would you hire a contractor to build a house and then demand that they start pouring a foundation the very next day?

Since the database is the cornerstone of pretty much every business project, if you don’t take the time to map out the needs of the project and how the database is going to meet them, then the chances are that the whole project will veer off course and lose direction. This additive nature is extremely important, not only for ease of development, but also for performance.

No future user of your design should need to wade through a 500 page document to determine the meaning of some wacky name.

Format and usability is important, but the primary battle is to have the information available and up to date.

At first glance, domain tables are just an abstract concept of a container that holds text. If the other case, you might have your domain table spread across many pages, unless you cluster on the referring table name, which then could cause it to be more costly to use a non-clustered index if you have many values.

The point of this tip is simply that it is better to do the work upfront, making structures solid and maintainable, rather than trying to attempt to do the least amount of work to start out a project. The problem is that too many designers use a surrogate key column as the only key column on a given table.

Rules that are optional, on the other hand, are wonderful candidates to go into a business layer of the application. Stored procedures make database development much cleaner, and encourage collaborative development between your database and functional programmers.

There is also a feature known as plan guides, which allow you to override the plan for a known query type.

However, the main point of this tip is that you should avoid coding very generic objects, such as ones that take a table name and twenty column names/value pairs as a parameter and lets you update the values in the table.

We can play our part in dispelling this notion, by gaining deep knowledge of the system we have created and understanding its limits through testing. What really gets the shaft in this whole process is deep system testing to make sure that the design you (presumably) worked so hard on at the beginning of the project is actually implemented correctly.

Too many database systems get tested like that car, with just a bit of poking around to see if individual queries and modules work. Now, it is far harder to diagnose and correct because now you have to deal with the fact that users are working with live data and trying to get work done.

For many data models, you will not save much space this way and storage for things like audit tables is inexpensive because it is rarely accessed except to append. What is the best approach to loading data into a tabular model – by using views or tables?

Please let me know if my answer is wrong; or exaggerates the importance of something; or has forgotten some important consideration. I also think it’s much easier to maintain a single database table containing the log information than a bunch of separate log files.

The ire raised by data tables is due, no doubt, to just how awful they can look when they’re not well designed. Proportional figures are designed to match the color — that is, the general sizing and spacing — of the typeface.

So if you have a table of primarily text, you’d want to keep things left-aligned, or if it’s primarily numbers, align things to the right. One other important aspect of audit tables that hasn’t been highlighted thus far, is that in addition to keeping track of who did what to which record (often including before and after snapshots) audit tables are write-once.

Audit tables are generally used when you want to track changes in sensitive/confidential tables.

But it should give you all the information needed to implement anything from simple versioning to full-on bi-temporal access.

Not only do you want to know who made a change and when, but when a bad change happens, you want a fast way to put the data back. In case, if you don’t have enterprise edition another database could make sense because it would “kind of” emulate piecemeal restore.

Now i created separate table same as original and insert new record to this table when any transaction happened in original. First 2 are masters and 3 is link table which includes userid and role id from previous tables.