This way we can have first number as 100001 and last number 110005. Unfortunately, this also affects unique indexes and no logic has been implemented to fix it. Hier findest Du Leute mit Deinen Interessen! The last row in the second table will never be deleted. What if we want to ensure all phone numbers are unique? Then use some reasonable number for optional highest value maybe olv + 100 or something like that. Maximum value of inserted id The maximum value of the inserted id depends on the type of numeric field we have selected. Despite this issue, unique indexes are useful in many situations and help you to retain data integrity when other programmers and users are not so conscientious! So take care while creating the auto increment field to match your future requirements.
The last row in the second table will never be deleted. Take YouTube for example they use a unique string to define a video, but that string is not the actual way they uniquely identify the video through out the database, and if they did the site would be slow because matching on strings is much slower than matching on unique ids. How about buy me a cup of coffee? The last row in the second table will never be deleted. . Does anybody confirm with this solution? Generating user id is working fine. April 7th, 2010 - Posted by Steve Marks to ,. Con: includes letters but probably won't include any naughty words.
Although you can only have one primary key, any number of unique indexes can be created with any number of fields. It seems to me that if I wanted to do this I would have to: Create a random number for the id, check to see if that id already exists in the database, if it does exist then create another random number and send yet another query to see if that exists, and so on. Does anybody confirm with this solution? Great — except that records 1 and 4 are identical. This way all the students will have six digit number. He's written more than 1,000 articles for SitePoint and you can find him.
Learn as if you were to live forever. Hier findest Du Leute mit Deinen Interessen! My first solution looks like this: I use a second table with an auto-increment-column, and add an insert trigger to the first table. Probably overhead, but you can be sure that you never generate a double uid. That way you'll get every next id higher than previous, it'll be somewhat randoms, but not more than +100 from previous id. My first solution looks like this: I use a second table with an auto-increment-column, and add an insert trigger to the first table. But if user id i exists in database, how can i generate new user id. All this will be done in single instance When user click on submit button from registration form.
We need not have to specify any thing in our query while adding the other details except auto incremented field data. A recent e-commerce project I was working on required me to generate a unique order reference number containing both letters and numbers for every new order placed. This we can take care while creating the table by adding auto increment value at the end. Unless you plan on a billion users, all methods described here are sufficiently fast for it not to be a problem. Limit: In the example, you can't have more than 90K users; adjust the numbers up or down to have a different limit. Does anybody confirm with this solution? Solution: Create the id, check to see if it is already in the table, if it is, then create another one.
Now let us try how to create a such auto incremented field. The inserted rows in this table are of no use and can be deleted if storage space is of concern. You should not be using this to create distinct member ids, because it is bad practice. I recommend thoroughy testing on a production-like test system first before moving to production. Or perhaps we could make the field a signed number and set -1. Con: May have leading zero.
Even having to check for dups takes only milliseconds. Con: Too easy to get dups. In a multi concurrent user environment, how to ensure that each new reservation activity gets an integer that is one larger than that of its immediate precursor? Does anybody confirm with this solution? Hmm, and what about a server crash? What you have should be used to create something like a username or user code. A 6 digit number is 1,000,000 posibilities, a 6 character alphanumeric string is 2,176,782,336 possibilities. You can use the rand function.
This could go on for ages. This probably won't be an issue until you have millions of users. First of all, I agree with the comments. In our example, we want to ensure no two records have the same country, area, number and extension. Generating a unique reference was easy, but what if the generated output already existed in the database? Read the details on how to get this number by visiting the tutorial here. Con: includes letters but probably won't include any naughty words. Con: bulky - 36 chars.