primary-key

问题 I am using SQL Server and creating a table (example is at the very bottom of this question). However I am having some issues understanding how primary keys actually work & how to use them properly. So I know a primary key ensures all the rows in a table are unique and that a primary key can't be null. I also read this page index basics - simple talk on indices and how indices are organised in a b-tree structure. So in my table for a row to have a unique value I would have to use the first 3

问题 I have this database structure CREATE TABLE `productinfo` ( `ProductID` int(11) NOT NULL AUTO_INCREMENT, `ProductName` varchar(255) NOT NULL, `ProductImage` varchar(255) NOT NULL, `CategoryID` int(11) NOT NULL, `SubCategoryID` int(11) NOT NULL, `ProductBrief` varchar(255) NOT NULL, `Features` text NOT NULL, `Specifications` text NOT NULL, `Reviews` text NOT NULL, `Price` varchar(255) NOT NULL, `Status` tinyint(4) NOT NULL, PRIMARY KEY (`ProductID`) ) ENGINE=MyISAM AUTO_INCREMENT=12 DEFAULT

问题 This question already has answers here : Identity increment is jumping in SQL Server database (6 answers) Closed 4 years ago . We're running SQL server 2012 SP1 x64 (11.0.3000.0) I have the following table with the InvoiceId field as the auto-incrementing, primary key: CREATE TABLE Orders( InvoiceId bigint IDENTITY(1001,1) NOT FOR REPLICATION, OrderId varchar(8) NOT NULL, ... -- other fields removed for brevity CONSTRAINT [PK_ORDERS] PRIMARY KEY CLUSTERED (InvoiceId) ON [PRIMARY], ) New rows

问题 Ok so essentially what I'm trying to do is add a q&a component to my website (first website, so my current php knowledge is minimal). I have the html page where the user's input is recorded, and added to the database, but then I'm having trouble pulling that specific info from the database. My current php page is pulling info where the questiondetail = the question detail ( detail='$detail' ) in the database, but that could potentially present a problem if two users enter the same information

问题 I'm trying to store arrays (or vectors) of data in a SQLite database but I'm having problems trying to find a decent way to do so. I found some other post on StackOverflow, that I can't seem to find anymore, which mentioned storing the data in a table like the following: CREATE TABLE array_of_points ( id integer NOT NULL, position integer NOT NULL, x integer NOT NULL, y integer NOT NULL, PRIMARY KEY (id, position) ); So to store all the data for a single array you would insert each item under

问题 I'm trying to store arrays (or vectors) of data in a SQLite database but I'm having problems trying to find a decent way to do so. I found some other post on StackOverflow, that I can't seem to find anymore, which mentioned storing the data in a table like the following: CREATE TABLE array_of_points ( id integer NOT NULL, position integer NOT NULL, x integer NOT NULL, y integer NOT NULL, PRIMARY KEY (id, position) ); So to store all the data for a single array you would insert each item under

问题 I am trying to add primary key to newly added column in existing table name Product_Details . New Column added: Product_Detail_ID ( int and not null ) I am trying add primary key to Product_Detail_ID (please note: there are no other primary or foreign key assigned to this table) I am trying with this query but getting error. ALTER TABLE Product_Details ADD CONSTRAINT pk_Product_Detils_Product_Detail_ID PRIMARY KEY(Product_Detail_ID) GO Error: The CREATE UNIQUE INDEX statement terminated

问题 The database-schema (Source and target) are very large (each has over 350 tables). I have got the task to somehow merge these two tables into one. The data itself (whats in the tables) has to be migrated. I have to be careful that there are no double entries for primary keys before or while merging the schemata. Has anybody ever done that already and would be able to provide me his solution or could anyone help me get a approach to the task? My approaches all failed and my advisor just tells

问题 I had a custom primary key that need to be set up on a particular data in a model. This was not enough, as an attempt to insert a duplicate number succeeded. So now when i replace primary_key=True to unique=True it works properly and rejects duplicate numbers!!. But according this document ( which uses fields ). primary_key=True implies null=False and unique=True. Which makes me confused as in why does it accept the value in the first place with having an inbuilt unique=True ? Thank you.

问题 I had a custom primary key that need to be set up on a particular data in a model. This was not enough, as an attempt to insert a duplicate number succeeded. So now when i replace primary_key=True to unique=True it works properly and rejects duplicate numbers!!. But according this document ( which uses fields ). primary_key=True implies null=False and unique=True. Which makes me confused as in why does it accept the value in the first place with having an inbuilt unique=True ? Thank you.