auto-increment

问题 I need two columns in table that would have same value on insert. Is there any way to do it from database side? 回答1: So you want to let one column use the auto_increment feature, but make another column in the same table also have the same value? I can't think of a reason you would need this feature. Perhaps you could explain what you're trying to accomplish, and I can suggest a different solution? A trigger won't work for this. It's a chicken-and-egg problem: You can't change any column's

问题 It appears that there is no concept of AUTO_INCREMENT in Oracle, up until and including version 11g. How can I create a column that behaves like auto increment in Oracle 11g? 回答1: There is no such thing as "auto_increment" or "identity" columns in Oracle as of Oracle 11g . However, you can model it easily with a sequence and a trigger: Table definition: CREATE TABLE departments ( ID NUMBER(10) NOT NULL, DESCRIPTION VARCHAR2(50) NOT NULL); ALTER TABLE departments ADD ( CONSTRAINT dept_pk

问题 Hi I am new in php and started learning. I am trying to increment variable value with 1 when submit button is pressed. My Code: <?php $i=0; if($_POST['submit']){ echo $i+1; } ?> Thanks 回答1: You're variable $i should be stored in session for example, so it won't lost its value when you submit the form. (You can check this answer Is PHP or PHP based web framework stateful or stateless?) Also when your script is executed, the first thing you do is $i = 0; so whenever you execute it, you

问题 I have been using int(10) and just noticed that Wordpress uses bigint(20) - What is different to use bigint(20) and int(10) for id auto increment? Which one should I use for id column? `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT, Vs `id` int(10) unsigned NOT NULL AUTO_INCREMENT, Thanks. 回答1: The difference is purely in the maximum value which can be stored (18,446,744,073,709,551,615 for the bigint(20) and 4,294,967,295 for the int(10), I believe), as per the details on the MySQL Numeric

问题 I have the below SQL I am trying to use to create a table and some columns. As part of it, I want two of the columns to autoincrement an integer. When I try using the below code it gives me an error. CREATE TABLE IF NOT EXISTS 'tasks' ( 'rowID' INTEGER, 'gID' INTEGER, 'task' TEXT, 'status' TEXT, 'position' INTEGER, 'updated' INTEGER, 'inlist' TEXT, 'deleted' TEXT, PRIMARY KEY AUTOINCREMENT ('rowID','position') ) When I remove the keyword "AUTOINCREMENT" from the SQL it works fine. Is it

问题 MySQL doesn't support multiple auto increment columns. CREATE TABLE IF NOT EXISTS `parts` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(255) NOT NULL, `order` int(11) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ; Is there another solution to make the value of column order increase automatically when I insert a new record? 回答1: You can do it from within your application by issuing another query that increases order or you can create a trigger

问题 I am looking to do a query like so: id | int | autoincrement something | varchar | 255 insert into `table` set something = concat('val', id); so that the table ends up looking like 1|val1 2|val2 3|val3... except that id always ends up being val0 for every row. How can I do this? 回答1: mysql> describe concattest; +-------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+------------------+------+-----+---------+----------------

问题 I am trying to make a column in a mysql database that auto increments by one but goes from 0-Z and then rolls. For example 000, 001, 002, ..., 009, 00A, 00B, ..., 00Z, 010, ..., 0ZZ, ..., 100. I would like to have the database create the column through an auto incrementing field. The ideas I have are: Create a column for each character that goes from 0-36, then auto increment row N (where N is the least significant digit) by 1. Then add a trigger on each column to add 1 to column N-1 when

问题 To illustrate my problem I will use the analogy of authors and books. I have 2 tables "author" and "books". Authors are unique and books are tied to a specific authors using a foreign key constraint. I was wondering if it was possible to have a column called "booknum" in the "books" table that auto-increment within the subset of a single author. So if the table has 100 rows and im inserting the 4th book of an author it puts a 4 into the "booknum" column. For example if the books table had 6

问题 When using MySQL START TRANSACTION and the decision is made by MySQL to roll back - In the case that a table had an AUTO_INCREMENT column - does the column get... decremented during the roll back? Or should it? I am having some issues where the transaction data is being properly rolled back - but it looks like the table was auto incremented and not decremented in the rollback. # BOTH TABLES START OUT EMPTY // TABLE1 ID is **auto_increment** START TRANSACTION; INSERT INTO `TABLE1` (`ID` ,`NAME