I need to setup 1000 test users in our DB. The users are named like this:
TestUser0001
TestUser0002
TestUser0003
And so on up to 1000. The thing is, I don't want to write 1000 insert statements to get this done. My approach was to use an IF/ELSE and use several variables so that I can check when the incremental value is within a range where I can put the appropriate zeros in place.
There has to be an easier way to do this, but I can't think of of it. The leading zeros are the biggest problem.
Anyone know of an easy way to accomplish this task? How would you do this?
The answer to this is to use FORMAT(). You could pass your variable that holds the incremented value into the FORMAT function and the format would be '0000'. Like so:
FORMAT(#IncVar, '0000')
Related
I'm trying to get some of the data provided to me clean enough to be evaluated. I've been provided with testing data that has special characters in it. For example, a large proportion has the value <0.5** or <0.5* indicating that the level of contaminant is below 0.5 PPM. However, this doesn't help much when I'm trying to evaluate that column.
I'm trying to figure out if the best way is to create a query and use that, or to create a new field and use an update query to remove the special characters. However, I can't figure out how to create a query from these values that can be evaluated numerically, and whenever I try and run an update query with Replace(Replace([SampleResult],"*",""),"<","") it doesn't output anything.
how can I generate a hash like this in mysql? Can I do it with INSERT statement?
00ee2f7f-4ead-4aaa-b29c-cc3f07ee2e94
I would like to add more records to a database, but I'm learning mysql now, and have no idea, how to generate something like this. Can it happen, that the same ID is generated?
Thx in advance!
Yes, there are lots of ways of generating the ID. That depends on what you need.
Yes it can happen the same id is generated. For the simple fact that you have an unlimited number of entries, and for each you use a 36 chars id (that is a limited number). So when you reach the end of the possibilities, one that was already generated will be generated again.
Also I presume you use mysql with something else (php maybe?), you can generate it there also.
Note: The more precise you describe what you need, the better answers you'll get.
I'm looking to make it easier for the clients to search for stuff like phone/mobile/fax numbers. For that to happen I want to strip both the search value and the relevant columns in my database of any non-numeric characters before comparing them. I'm using these functions to get only the numeric elements of the strings in mysql but they slow my queries down to a crawl when I use them.
Is there any way to do it without blowing my run times sky high?
The reason why your query times are exploding is because any use of such functions disables you from using any index. Since you are not searching directly on a field, but on the output of a function, there is no way mySQL can use an index to execute the query.
This is in addition to the fact that you have to compute the function output for each record.
The best way around these runtimes, if you have access and permission to do so, is to add a new column with the content you're filtering. Add a WRITE trigger to fill the column with the stripped values, run a script that updates the field once for all records. Add an index and include the new column. Then, in your application, use the new column for searches for a number value of a telephone. Downsides are table schema alterations and added code for the business logic and/or data abstraction layer.
I'm looking for the best way to basically get a unique number (guaranteed, not some random string or current time in milliseconds & of a reasonable length about 8 characters) using MySQL (or other ways suggestions welcome).
I just basically want to run some SELECT ... statement and have it always return a unique number with out any inserting into database. Just something that increments some stored value and returns the value and can handle a lot of requests concurrently, without heavy blocking of the application.
I know that I can make something with combinations of random numbers with higher bases (for shorter length), that could make it very unlikely that they overlap, but won't guarantee it.
It just feels like there should be some easy way to get this.
To clarify...
I need this number to be short as it will be part of a URL and it is ok for the query to lock a row for a short period of time. What I was looking for is maybe some command that underhood does something like this ...
LOCK VALUE
RETURN VALUE++
UNLOCK VALUE
Where the VALUE is stored in the database, a MySQL database maybe.
You seek UUID().
http://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html#function_uuid
mysql> SELECT UUID();
-> '6ccd780c-baba-1026-9564-0040f4311e29'
It will return a 128-bit hexadecimal number. You can munge as necessary.
Is the unique number to be associated with a particular row in a table? If not, why not call rand(): select rand(); The value returned is between zero and one, so scale as desired.
Great question.
Shortest answer - that is simply not possible according to your specifications.
Long answer - the closest approach to this is MySQL's UUID but that is neither short, nor is sortable (ie: a former UUID value to be greater/smaller than a previous one).
To UUID or not to UUID? is a nice article describing pros and cons regarding their usage, touching also some of the reasons of why you can't have what you need
I am not sure I understand exactly, maybe something like this:
SELECT ROUND(RAND() * 123456789) as id
The larger you make the number, the larger your id.
No guarantees about uniqueness of course, this is a quick hack after all and you should implement a check in code to handle the off chance a duplicate is inserted, but maybe this would serve your purpose?
Of course, there are many other approaches possible to do this.
You can easily use most any scripting language to generate this for you, php example here:
//Generates a 32 character identifier that is extremely difficult to predict.
$id = md5(uniqid(rand(), true));
//Generates a 32 character identifier that is extremely difficult to predict.
$id = md5(uniqid(rand(), true));
Then use $id in your query or whatever you need your unique id in. In my opinion, the advantage of doing this in a scripting language when interacting with a DB is that it is easier to validate for application / usage purposes and act accordingly. For instance, in your example, whatever method you use, if you wanted to be 100% always sure of data integrity, you have to make sure there are no duplicates of that id elsewhere. This is easier to do in a script than in SQL.
Hope that helps my friend, good-luck!
I currently have a table in MySQL that stores values normally, but I want to add a field to that table that stores an array of values, such as cities. Should I simply store that array as a CSV? Each row will need it's own array, so I feel uneasy about making a new table and inserting 2-5 rows for each row inserted in the previous table.
I feel like this situation should have a name, I just can't think of it :)
Edit
number of elements - 2-5 (a selection from a dynamic list of cities, the array references the list, which is a table)
This field would not need to be searchable, simply retrieved alongside other data.
The "right" way would be to have another table that holds each value but since you don't want to go that route a delimited list should work. Just make sure that you pick a delimiter that won't show up in the data. You can also store the data as XML depending on how you plan on interacting with the data this may be a better route.
I would go with the idea of a field containing your comma (or other logical delimiter) separated values. Just make sure that your field is going to be big enough to hold your maximum array size. Then when you pull the field out, it should be easy to perform an explode() on the long string using your delimiter, which will then immediately populate your array in the code.
Maybe the word you're looking for is "normalize". As in, move the array to a separate table, linked to the first by means of a key. This offers several advantages:
The array size can grow almost indefinitely
Efficient storage
Ability to search for values in the array without having to use "like"
Of course, the decision of whether to normalize this data depends on many factors that you haven't mentioned, like the number of elements, whether or not the number is fixed, whether the elements need to be searchable, etc.
Is your application PHP? It might be worth investigating the functions serialize and unserialize.
These two functions allow you to easily store an array in the database, then recreate that array at a later time.
As others have mentioned, another table is the proper way to go.
But if you really don't want to do that(?), assuming you're using PHP with MySQL, why not use the serialize() and store a serialized value?