primary-key

问题 database= mysql language=php I am coding program to work like this PC1 =computer1 step 1.PC1 insert data ,new ID from Auto-increment. 2.PC1 select last ID everything work fine but.. The problem when your code is used by many computers at the same mili-sec. For example PC1insert data,Auto-increment new ID 2.PC2 insert data ,Auto-increment new ID 3.PC1 select last ID <-------Wrong 4PC2 select last ID How to config database or modify php code to prevent this , thankyou. 回答1: You should use mysql

问题 I have a SalesTransaction and an Invoice table: Create Table SalesTransaction ( SalesTransactionId int Identity(1,1) Primary Key, CustomerId int Foreign key references Customer(CustomerId) , ProductId int Foreign key references Product(ProductID), Price money, Quantity int, Total money, InvoiceId int ) and Create Table Invoice ( InvoiceId int Primary Key, InvoiceAmount money Not Null , BalanceAmount money, AmountPaid money Not Null ) What I want is the Invoiceid from Invoice table to tag

问题 EDIT: Okay the error reoccurred again and I know exactly what caused it this time but not sure why. Here is the error screen: This happened after adding a composite unique index. Before that it was showing the records fine. CreateIndex("dbo.Fixtures", new[] { "MarketId", "BookName", "CoupName" }, unique: true, name: "IX_UniqueFixture"); That's the only change I made to try to enforce uniqueness and it messed up with Datatables display. I have a very simple structure. Two tables. One parent,

问题 I have the following common tables with the relationships setup in a many to many fashion in my entity model: Users - UserCodePK, UserName UserGroups - UserCodeFK,GroupCodeFK Groups - GroupCodePK,GroupDescription My Code when trying to add a user: public static string CreateUser(User user) { using (var dbContext = new DCSEntities()) { User u = new User { UserCodePK = "NewUser", txtUserName = "New User Name }; u.Groups.Add(new UserGroup {GroupCode = "ADMIN"}); u.Groups.Add(new UserGroup

问题 So I'm designing a function that inserts a row into the MySQL database. The table has a Primary key with Auto-Increment enabled. So I don't insert the value of this column. But the PK is the only unique column of the entire table. How can I fetch the row I just inserted? I don't see a problem if the function is in light traffic, but when its load is heavier and heavier, I can see a potential bug: say I inserted a row and the DB's AI value is 1, then before the fetch function starts to request

问题 In one sentence: Statement.getGeneratedKeys() is occasionally returning an empty ResultSet , and I'm trying to figure out why. Background: I am keeping track of users' requests regarding orders and some of their items. I have two tables, call them Header and Detail . To link the header and details properly, Header has a SERIAL column named request_id , which I use when inserting rows into Detail . This has been working fine for a long time (as far as I know), but recently I noticed that

问题 I'm new in Neo4j an I need some help. I'm trying to make constraint in multiple properties of nodes at once per two meanings: I need to specify as constraint many properties without typing again and again all over the properties with the command I need to define many properties as ONE- UNITY constraint like in SQL when 3 attributes is a primary key and not separably. How can I achieve it? 回答1: You are actually asking 2 questions. The APOC procedure apoc.schema.assert is helpful for

问题 I've got a running database but the primary key won't auto increment. Does anyone know what the problem could be? The code is as following // Database name and Version private static final String DATABASE_NAME = "kmky_database.db"; private static final int DATABASE_VERSION = 1; // Database Table private static final String TABLE_NAME = "logs"; private static final String COLUMN_ID = "_id"; private static final String COLUMN_PHONENUMBER = "phonenumber"; private static final String COLUMN_TYPE

问题 I have a table of orders and I want to give users a unique code for an order whilst hiding the incrementing identity integer primary key because I don't want to give away how many orders have been made. One easy way of making sure the codes are unique is to use the primary key to determine the code. So how can I transform an integer into a friendly, say, eight alpha numeric code such that every code is unique? 回答1: Assuming the total number of orders being created isn't going to get anywhere

问题 When I inspect the Trac database I get: class TicketChange(models.Model): ticket = models.IntegerField() time = models.BigIntegerField() author = models.TextField(blank=True) field = models.TextField() oldvalue = models.TextField(blank=True) newvalue = models.TextField(blank=True) class Meta: managed = False db_table = 'ticket_change' With not primary key: >>> TicketChange.objects.all() DatabaseError: column ticket_change.id does not exist LINE 1: SELECT "ticket_change"."id", "ticket_change".