sql primary key autoincrement

Database:Warehouse where data is stored, data is classified by tableFeatures: mass storage, fast searching, control of concurrency problems, security, data integrity (the data stored in the database is correct and true)database software: DBSM Database Management SystemCommon database software: MySQL MSSQL Server Oracle AccessSQL: Structured Query Language Structured Query Language features: Simple language, easy to learn and easy to use.SQL Server: is a large network-based database software. The

Both the Primary key and the unique key are unique constraints. But there's a big difference:1, Primary key 1 or more columns must be NOT NULL, if column is null, when the Primary key i

compare the values stored in the preceding table on the master and slave servers, and you will find that the master and slave data are consistent in the command line mode and in the row/hybrid mode; Suggestion: In the replication mode, if you need the UUID () function, you must use the row/hybrid replication mode. Glossary: When the input parameters are the same and executed at the same time or multiple calls in an SQL statement, different worthwh

/// /// Query Method/// /// /// Public dataset query (string tabnames, string columnname){Using (oraclehelper orahp = new oraclehelper ()){String [] tabs = tabnames. Split (',');Dataset DATA = new dataset ();Orahp. open ();For (INT I = 0; I {String tabtemp = tabs [I];String SQL = "select nvl (v. foreign key table, '"+ tabtemp +"') as foreign key table, AC. column

) values (1, 3), (1, 7) on duplicate key update c = values (C ); After the execution, the value of C will change to 7 (the second repeat with the first repeat, and C will take the repeat value 7 directly ).Note: On duplicate key update is only a special MySQL syntax, not a standard SQL syntax!This syntax is applicable to scenarios where you need to determine whet

and deleting tables -- after creating a table, you can only add and delete tables, but cannot modify them. 2.1 Add alter table emp1 add constaint emp1_sal_ck check(salary > 0) 2.1.1 for not null, you do not need to add. You need to use modify: alter table emp1 modify (salary not null) 2.2 Delete alter table emp1 drop constaint emp1_sal_ck 2.3 invalidate a constraint: the constraint still exists in the table, but does not work. Alter table emp1 Disable constraint emp1_ema

further explained: We need to modify the following SC table foreign key Declaration, add the name of the foreign key constraint, to facilitate our subsequent masking and recovery of foreign KEY constraints: create table SC (s# integer , C # integer , Scor E integer , constraint sidfk foreign key (

: We need to change the following SC table foreign key Declaration, add the name of the foreign key constraint, so that we might block and restore foreign KEY constraints: create table SC (s# integer , C # integer , Score Span class= "Hljs-keyword" >integer , constraint sidfk foreign key (s#) referen

When I has do some SQL Tody, some confusion come up to me.Its on the index PRIMARY key UNIQUE key in MySQL. So I Google it for the answers. There is a clearly answer on theStackOverflow. So I share it in this BLOG.About INDEX:Firstly, we should understand KEY and INDEX is

zero, you only need to modify the Sqlite_sequence table. UPDATESqlite_sequenceSETSeq= 0 WHEREName='TableName'or you can delete the record directly:DELETE fromSqlite_sequenceWHEREName='TableName'To zero the self-increment columns of all tables, empty the Sqlite_sequence table directly:DELETE fromsqlite_sequence; SQLite in integerPRIMARY KEYthe use of AutoIncrement and ROWID in the design of the table with SQLite, suddenly think of a problem, is that

When you use MyBatis to do a persistence layer, the INSERT statement defaults to not return the primary key value of the record, but instead returns the number of record bars inserted, which can be configured to perform if the business layer needs to get the primary key for the record For sequence

1, the creation of the primary keyMethod One: Declare the field PRIMARY KEY constraint directly in the SQL statementCREATE TABLE table_name (ID type[length] constraint pk_name primary key,name tyoe[length],age type[length],class_i

My BSOOC need a query table primary key foreign key information of SQL, last night research to 1 o'clock in the morning, finally can achieve this goal: Oracle: Select O.obj# as ObjectId, o.name as TableName, oc.name as ConstraintName, Decode (c.type#, 1, ' C ', 2, ' P ', 3, ' U ', 4, ' R ', 5, ' V ', 6, ' O ', 7, ' C '

I summarize the 3 kinds:1. According to the front desk to obtain the WID number to the background to the activity of foreign key table data back, get wname;2. Add the property public string Wname{get;set in the Entity Class primary key table model, and join Model.wname to return the display when the BLL business logic is acquired at the front end;3. Inline query

1. Overview: In our database design, the primary key of database is essential, the design of the primary key has a great influence on the design of the whole database. I'll compare the performance of the AutoIncrement field with the GUID field, and welcome the discussion. 2.

illustrate how to use inner joins and nested queries to implement multi-table queries. In fact, all databases are the same, and SQL statements are generic.I. BASIC OBJECTIVESIt is known that in the test database, the school database can be self-contained, the following table exists:(1) The student table I_student, which records the data of all the students in the school, indicates that there are 3 students in the school a,b,c(2) Class table I_class,

the underlying database, so all databases are available.The principle of generating primary key of increment can infer that this kind of primary key generation policy does not apply to a system with large number of users concurrent access at the same time period, when a large number of users simultaneously insert oper

because it is simple to use. Automatic growth allows us to add data to the database, regardless of the primary key value, after the record is inserted, the database system will automatically assign a value to ensure that there is absolutely no duplication. If you use a SQL Server database, you can also use the @ @IDENTITY global variable to get the

In our database design, the primary key of the database table is unavoidable. Many may not think deeply about it. The design of the primary key has a great impact on the design of the entire database, therefore, we have to pay attention to it. Necessity of primary

Some SQL (under Oracle) summaries used in the project: 1. Find all indexes of the table (including index name, type, constituent column) 1 Select T.*,i.index_type from User_ind_columns t,user_indexes i where t.index_name = I.index_name and T.tab Le_name = i.table_name and t.table_name = table to query2. lookup table's primary key (including name, constituent col