auto-increment

问题 Can i adjust the value of an auto-incremented field in the database automatically? I have a table called "post" which has a field called "pid" which is set to auto-increment. Posts from this table may be deleted by the user at a later time, but the auto- incremented value will not be adjusted. Is there a way to adjust the pid field everytime posts are deleted? for eg:If i have 4 entries: pid=1,2,3,4(pid-auto-increment) Now if i delete 2, is there a way to update 3 to 2 and 4 to 3 and so on ?

问题 Can i adjust the value of an auto-incremented field in the database automatically? I have a table called "post" which has a field called "pid" which is set to auto-increment. Posts from this table may be deleted by the user at a later time, but the auto- incremented value will not be adjusted. Is there a way to adjust the pid field everytime posts are deleted? for eg:If i have 4 entries: pid=1,2,3,4(pid-auto-increment) Now if i delete 2, is there a way to update 3 to 2 and 4 to 3 and so on ?

问题 I want to add an auto_increment column in an oracle database using liquibase script. I have tried using the auto_increment attribute in liquibase : <column name="SUPPLEMENT_ID" type="INTEGER" autoIncrement="true" > <constraints primaryKey="true"></constraints> </column> If oracle supports auto_increment, how can I achieve it using liquibase scripts? 回答1: IDENTITY columns are introduced in oracle 12c which allows users to create auto increment columns But if you are using older versions you

问题 I want to add an auto_increment column in an oracle database using liquibase script. I have tried using the auto_increment attribute in liquibase : <column name="SUPPLEMENT_ID" type="INTEGER" autoIncrement="true" > <constraints primaryKey="true"></constraints> </column> If oracle supports auto_increment, how can I achieve it using liquibase scripts? 回答1: IDENTITY columns are introduced in oracle 12c which allows users to create auto increment columns But if you are using older versions you

问题 Closed . This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 4 years ago . Improve this question I'd like to create a column in my mysql database which auto increments in response to a specific value being entered into another column. For example (data below), when a new record is created by a student using the site, he/she would input the name of their class and be

问题 I want to add a column to a mysql table where its cells will get values like: newColumn ----------- log-00001 log-00002 log-00003 .... the values log-0000x will automatically be created by mysql. This is like an "auto incremented" column but with the 'log-' prefix. Is this possible? Thx 回答1: MySQL doesn't auto-increment anything other than integers. You can't auto-increment a string. You can't use a trigger to populate a string based on the auto-increment value. The reason is that the auto

问题 I want to add a column to a mysql table where its cells will get values like: newColumn ----------- log-00001 log-00002 log-00003 .... the values log-0000x will automatically be created by mysql. This is like an "auto incremented" column but with the 'log-' prefix. Is this possible? Thx 回答1: MySQL doesn't auto-increment anything other than integers. You can't auto-increment a string. You can't use a trigger to populate a string based on the auto-increment value. The reason is that the auto

问题 This question already has answers here : serial in postgres is being increased even though I added on conflict do nothing (4 answers) Closed 5 months ago . duplicate of this question Say I have the following table things. I want unique names in the table so there are no duplicates. The process that inserts a thing shouldn't need to check if a thing with this name is already there. CREATE TABLE things( id SMALLSERIAL PRIMARY KEY, name varchar UNIQUE ); When I insert values like this it works.

问题 Here's the SQL I've tried so far to create the table CREATE TABLE tblPosts (nId INTEGER PRIMARY KEY GENERATED ALWAYS AS IDENTITY, strContent VARCHAR(140) NOT NULL, strLink VARCHAR(200), strImage VARCHAR(200)); using String sql = "INSERT INTO tblPosts VALUES ('" + textFieldContent.getText() + "', '" + textFieldLink.getText() + "', '" + textFieldImage.getText() + "')"; I get an error telling me I'm not providing the nId column value which I'm not but if the column auto-increments I'm not

问题 I want to have an additional ID field in my mongodb collection. The objectId is perfect for get unique IDs, but I need shorter IDs for my user management. These IDs should look like 100001 , 100002 and so on. Is it possible to get these by auto increment? Thx 回答1: MongoDB does not have an auto increment functionality. You could solve this by keeping track the 'id' in a separate collection called 'user_sequence' and store a custom function in MongoDB to get the next value. Take a look at: