Auto_Increment
Hello, I wonder if you can help me. For a university project I've got a database with several tables using columns set up with 'auto_increment'. I've discovered that the value that the system creates for a new record is one greater than the largest one which has existed even if the records with the largest values have been deleted. I've read the docs and read the part which says that this is the way myISAM tables handles auto_increment and that ISAM tables create a value which is one greater than the largest value currently existing. >From this I've presumed that I'm using myISAM tables but is there any way I can make the auto_increment feature work the way it does with the ISAM tables? And what exactly are myISAM and ISAM tables? (a quick web search gave me: -the Information centre for South African Music -the Institute for the Study of American Music -International Swimwear and Active Market) Thanks for any help you can give me, Jamie. - Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
Ships and Harbours
Hello all, I'm trying to write what should be a simple query but is turning out to be a particularly difficult one and was wondering if I could ask your advice. The problem is to do with some harbour management software I'm writing for a university software course. I have a table which gives the distances (in metres) along a harbour of the front-end and back-end of where each ship will dock, and the date and time of when each will arive and depart. What I am trying to find is the areas of empty space along the harbour between a given date and time range. So far I have managed to write a query which returns the occupied spaces (i.e. the positions where ships will be docked) for a given time range. A graph of the harbour distance against time looks something like: 0m Distance Along Harbour 1200m TIME -- 0m->200m 350m->600m 900m->1100m 500m->700 1XXX 2X X 3X XXXX 4X XX X X X 5??? 6X XX X aaX X 7XXXX X aaX X 8 XXX aaX X 9 aaX X 10 XXXaaX X 11 X XaaX X 12 X XaaX X 13 ??? 14 X X X X 15 X X 16 XXX 'X' is for the outline of the ship's position over time. 'a' is the area of free space within a given time range that I would like the query to return. '?' represents the boundaries the time range I'm checking. Any white space which doesn't stretch the whole time range is irrelevant as I need the space for the entire time. I'm using a table containing (amongst other things): shipArrivalDate (DATETIME) shipDepartDate (DATETIME) startPosition (given in metres from the 0m end of the harbour) endPosition(given in metres from the 0m end of the harbour) (These distances are illustrated above) I can get a table of the start and end positions of all ships in the time range but converting this into the free space start and end positions has become a bit of headache. Any ideas you can give will be much appreciated, Jamie. - Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
Setting a specific default value on a field
Hello all, I'm a third year uni student in Scotland doing a year long project which involves a fair amount of MySQL. I have the following problem and would be appreciative if I could get some advice on solving it: - in the script I run to create a table how do I code one DateTime field to intially be set to a value of another DateTime field? More specifically, I have two DateTime fields (A and B), in my creation script I want to set the default value of B to the value of A so that when I write a new record to the table the position of B can be left NULL, or equivalent, but the value of A will be stored in it's place. I later on want to change B independently to a different value than A so I don't want a strict contraint that they must always be the same. Thanks, Jamie. - Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
