In Microsoft Dynamics CRM 2011, I want to create a duplicate rule that consists of several fields. However, when I try to save the rule it shows an error that says that the total length of the duplicate rule is too large (maximum is 450). How do I get around this problem?
Well, first of all you can't get around the limit of 450 characters. Your only option is thus to define your duplicate rule to be within the limit. First, you should ensure that there aren't any fields in the duplicate rule that aren't strictly necessary. If you have removed these and you still exceed the maximum length, there is a trick that you can apply.
Some of the CRM fields have very large lengths. For some fields, this maximum length will probably never be reached. The trick is to change the duplicate rule from being an exact match to one that only checks the first X characters. Now, only the X characters will count towards the duplicate rule length and you thus have reduced the length.
An example field where you might be able to apply this trick is the zipcode field, which has a length of 21 characters. By default, including this field as an exact match in your duplicate rule would add 21 to the length of the duplicate rule. However, most countries use zipcodes with far less characters. In our system, zipcodes are always defined using 7 characters, never more. We thus can safely change its duplicate field match rule to only match on the first 7 characters, thereby reducing the overall duplicate rule length by 14 characters.
Related
I have a table in which i have a field that requires 3 letters and 3 numbers (that have to between the values 2000 & 7000).
I've been reading around, and i'm still not sure which is the better way to handle this issue, whether it can be with a simple datatype, say for instance char(6), or if there has to be a field that contains only the 3 letters, and another field that contains the 3 numbers with a check restriction to ensure that the values of that field are between 2000 & 7000.
Any help that you can offer me, i would be glad. Thanks in advance
You may have to give more specificity about the requirements, but it sounds to me like a single column is the best option -- especially if order matters. If the letters and numbers have meanings separately, then they should be in two columns. Otherwise, you'll just end up having to concatenate them together.
char(6) is fine as long as you know it will always be 6 characters exactly. You can't enforce such a specific limit as 2000 to 7000 at column level anyway (which is 4 numbers, isn't it?)
Every field should represent an attribute of the entities the table holds. In other words, if these three letters and three numbers represents different attributes, they should be in separate fields, otherwise (e.g. they are to represent a serial number) you can have them in one field.
Another approach is to think of a possible use case, like: Am I going to perform a query based on the second number? If your answer is yes, then they should be in separate fields, otherwise they represent one attribute and they should be in one field.
Hope it helps.
If the value is "one" value, use one column, say char(6), but...
Here's a surprising fact: mysql doesn't support CHECK constraints!
Mysql allows CHECK constraints to defined, however they are completely ignored and allowed only for comparability with SQL from other databases.
If you want to enforce a format, you'll need to use a trigger, but mysql doesn't support raising exceptions, so you'll have to use a work-around.
The best option is probably to use app code for validation.
I've read the more nuanced responses to the question of how many columns is too many and would like to ask a follow up.
I inherited a pretty messy project (a survey framework), but one could argue that the DB design is actually properly normalized, i.e. a person really has as many attributes as there are questions.
I wouldn't defend that notion in a debate, but the more pressing point is that I have very limited time, I'm trying to help users of this framework out and the quickest fix I can think of right now is reducing the row size. I doubt I have the skill to change the DB model in the time I have.
The column number now is 4661, but they can hopefully reduce it to at least 3244, probably less (by reducing the actual number of questions).
The hard column limit is 4096, but right now I don't even succeed in adding 2500 columns, presumably because of the row size limit which is 65,535 bytes.
However, when I calculate my row size I end up with a much lower value, because nearly all columns are TINYINTs (survey responses ranging from 1-12).
It doesn't even work with 2000 TINYINTs (an example query that fails).
Using the formula given in the documentation I get 4996 bytes or less.
column.lengths = tinyints * 1
null.columns = length(all.columns)
variable.lengths.columns = 0
(row.length = 1+
(column.lengths)+
(null.columns + 7)/8+
(variable.lengths.columns)
)
## 4996
What did I misunderstand in that row length calculation?
I overlooked this paragraph
Thus, using long column names can reduce the maximum number of
columns, as can the inclusion of ENUM or SET columns, or use of column
or table comments.
I had long column names, replacing them with sequential numbers allowed me to have more columns (ca. 2693), I'll have to see if the increase is sufficient. I don't know how they're saved, presumably as strings, so maybe I can reduce them even further using letters.
Here is something that troubles me as I am creating a database table columns. For each of these there is a data type which has it's length. For e.g say one of the tables is a file path, and I assume this file path to be not longer than 100 in length at max, obviously i specify this as
filepath Varchar(100)
However, this still takes the same amount of memory space as say varchar(255) which is 1 byte. Given this, what is the benefit of me specifying the length as 100. Taking an outlier example, if my filepath exceeds varchar(100), does the database reject/trim down the filepath value to fit it to 100? Or does it allow it to exceed beyond 100 since the allotted memory space is still around 1 byte?
Essentially the above explanation frames my question as should one try and be very specific about the expected maximum length for a table column? Or just play it safe and specify the upper limit of the expected length of the table column depending on the memory requirement ?
Thanks much !
Parijat
MySQL will auto-truncate the value down to 100 characters. The number in the brackets for text/char fields is the MAXIMUM length. Note that this is a CHARACTER limit. If you've got a multibyte collation on that field, you can store more than 100 bytes in the field, but only 100 characters worth of text.
This is different than saying int(10), where the bracketed number is for display purposes only. An int is an int internally and takes up 16bits, regardless of how many digits you allow with the (#), but you'll never SEE more than those # digits.
very specific about the expected maximum length for a table column? Or just play it safe
If one would make a table containing addresses, you undoubtedly know that there will be some kind of limit to the length of the address. It would be useless to allow longer fields in the database.
You should play it safe, and be very careful.
This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
List of standard lengths for database fields
Simple as that, what should be the typical length of allowed "Full Name" of a user in database?
When I create users table, I usually set it as varchar 31 or 32 (according to performance). What do you guys use and what's standard/typical convention.
Sidenote: I never face problem in email length (as I set it 254) and password (hash, 32 length).
The maximum your average varchar field allows (254?).
You are not winning anything by making it arbitrarily shorter. The fine-grained size controls on numbers and chars are more or less a relic from the past, when every byte mattered. It can matter today - if you are dealing with tens or hundreds of millions of rows, or thousands of queries per sec. For your average database (i.e. 99% of them) performance comes from proper indexing and querying, NOT making your rows a couple of bytes smaller.
Only restrict the length of a field when there is some formal specification that defines a maximum length, like 13 digits for an EAN code or 12 characters for an ISIN.
Full name is always a computed column composed of first, middle, last, prefix, suffix, degree, family name, etc in my designs. The list of individual columns are determined by the targeted local of the app. The display length of 'Full Name' is normall contained within the app design not the database. There is not any space savings in SQL Server between varchar(32) and varchar(256). Varchar(256) is my choice.
I never want to be in the meeting when someone says "Your db design will not hold all our data".
You are always assigning an ID to the user so you can join and do look-ups using the ID instead of the FullName, correct?
I would recommend at least 128.
Well you can just put it at 255 if you want.
varchars is a Variable length storage type. This means theres 1 byte which stores the actual length of the string, varchars dont use up more bites then needed so storage wise it really does not matter. This is described on the mysql page
Description can be found here http://dev.mysql.com/doc/refman/5.0/en/char.html
It is illustrated halfway the page check the table.
VARCHAR values are not padded when
they are stored. Handling of trailing
spaces is version-dependent. As of
MySQL 5.0.3, trailing spaces are
retained when values are stored and
retrieved, in conformance with
standard SQL. Before MySQL 5.0.3,
trailing spaces are removed from
values when they are stored into a
VARCHAR column; this means that the
spaces also are absent from retrieved
values.
Conclusion:
Storage wise you could always go for 255 because it wont use up additional space and you wont get intro trouble with string getting cut off.
Greetz
I just added a new field to my table in mysql and it came back with a warning of "1117: too many columns"
The table has (gasp) 1449 columns. I know, I know it's a ridiculous number of columns and we are in the process of refactoring the schema but I need to extend this architecture just a bit more. That said, this doesn't seem to be reaching the theoretical limit of 3398 as per the mysql documentation. We are also not close to the 64K limit per row as we are in the 50K range right now.
The warning does not prevent me from adding fields to the schema so not sure how it fails if at all. How do I interpret this error given that it does not seem to cause any issues?
Perhaps some of these factors are adding to the total byte count:
http://dev.mysql.com/doc/refman/5.5/en/column-count-limit.html
e.g., if a column allows nulls, that adds to the total or if unicode is used, that more than triples the space required by character columns, etc...
for MyISAM:
row length =
1 +
(sum of column lengths) +
(number of NULL columns + delete_flag + 7)/8 +
(number of variable-length columns)
you could check if it's indeed a row size issue or a column count issue, by adding just a tinyint not null column, then dropping that and adding a char(x) column until you get the error.
If it is a warning as you say, then you should remember that warnings are exactly that: warnings. It means you're okay for now but, if you continue with the behaviour that elicited the warning, you will probably be punished in one form or another.
However, it's more likely that this is an error in that it's refused to actually let you add more columns. Even if it does let you add more columns, that's unlikely to last for long.
So, regardless of whether it's a warning or error, the right response is to listen to what it's telling you, and fix it.
If you need a quick'n'dirty fix while you're thinking about the best way to fix it properly, you can split the row across two tables with a common identifier.
This will make your queries rather ugly but will at least allow you to add more columns to the "table" (quoted because it's actually two tables with a common key).
Don't use this as a final solution, not least of all because it breaks normalisation rules. But, to be honest, with more than a thousand columns, there's a good chance they're already broken :-)
I'm finding it very hard to imagine an item that would have thousands of attributes that couldn't be organised into a better hierarchy.