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Postgresql has the following three ways to set the primary key increment, the following look at the same point and different points.--Method OneCREATE TABLE Test_a(ID Serial,Name character varying (128),Constraint pk_test_a_id primary key (ID));Notice:create
constraint that is automatically defined. Note that each table can have multiple UNIQUE constraints, but there can be only one PRIMARY KEY constraint per table. CREATE TABLE Persons
(
UNIQUE ,
LastName varchar (255) Not NULL,
F
Modify the Data Type of the column corresponding to the primary key of an Oracle database table
When upgrading our product from SPC100 to SPC200, because the data type of the database table column has changed, you need to write an SQL script to complete the Database Upgrade
Modify the Data Type of the column corresponding to the primary key of the Oracle database table.
When upgrading our product from SPC100 to SPC200, because the data type of the database table column has changed, you need to write an SQL script to complete the Database Upgra
I hope that I can clearly analyze the primary and foreign key tables and field information like SQL Server, use an SQL statement to write out the one-to-one correspondence between the fields in the primary and foreign
Most databases have many primary keys, but the same primary key of two records cannot have the same value in a table. You can use Java database connectivity (JDBC) to determine the primary key of a data
when inserting data into a table, if the primary key is a self-growing type, then we can not assign a value to the primary key column, but sometimes the primary key is exactly the forei
Use after an SQL statement
SCOPE_IDENTITY ()
Of course, you can also use SELECT @ IDENTITY
However, the use of SELECT @ IDENTITY is globally up-to-date. incorrect values may be obtained.
Example:Copy codeThe Code is as follows: insert into dbo. SNS_BlogData (userName) values ('jiangyun ');SELECT SCOPE_IDENTITY ()
Gets the primary key return value for the insert
= male) Five. Set the CHECK constraint. Check Age int check (age between), Six. Auto-grow. Auto_increment to be used on the primary key: Create TABLE box (ID int auto_increment primary key) Seven. Foreign
Primary Key of the InnoDB Storage engine table
In the InnoDB Storage engine, tables are organized and stored in the order of primary keys. In an InnoDB Storage engine table, each table has a
key value can be changed, the uniqueness of the primary key may be damaged by accidental input of used values.
9. the best way to create a primary key is to create a column that co
--Delete foreign keysSyntax: ALTER TABLE name DROP constraint foreign KEY constraint nameSuch as:ALTER TABLE STU_PKFK_SC DROP constraint fk_sALTER TABLE STU_PKFK_SC DROP constraint Fk_c--Add foreign keysSyntax: ALTER TABLE name ADD constraint foreign
When I added a primary key to a Mysql table, I used the following SQL statement:
AlterTable'Table name'AddColumn'Column name'IntNotNullAuto_increment comment'Primary key'Before 'a column name ';
The following two errors are returned:
Error Code: 1064
You have an error in your
Use after an SQL statementSCOPE_IDENTITY ()Of course, you can also use SELECT @ IDENTITYHowever, the use of SELECT @ IDENTITY is globally up-to-date. incorrect values may be obtained.Example:Copy codeThe Code is as follows:Insert into dbo. SNS_BlogData (userName) values ('jiangyun ');SELECT SCOPE_IDENTITY ()Gets the primary key return value for the insert into op
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