CREATE TABLE Employees : Specifies the creation of a new table named Employees.EmployeeID INT PRIMARY KEY : Defines the EmployeeID column as an integer and sets it as the primary key to ensure each record is uniquely identifiable.Name VARCHAR(100) NOT NULL : Defines the Name column as a...
SQL UNIQUE Constraint on ALTER TABLE
SQL PRIMARY KEY Constraint on CREATE TABLE 下面的 SQL 在“Persons” 表创建时在 “Id_P” 列创建 PRIMARY KEY 约束: MySQL: CREATETABLEPersons(Id_PintNOTNULL,LastNamevarchar(255)NOTNULL,FirstNamevarchar(255),Addressvarchar(255),Cityvarchar(255),PRIMARYKEY(Id_P)) 1. 2. 3. 4. 5. 6. 7. ...
If the name of a history table is specified during history table creation, you must specify the schema and table name. If the history table doesn't exist, the system generates a new history table matching the schema of the current table in the same filegroup as the current table, creating...
We can implement theUNIQUEconstraint at the time of table creation. For example, -- create a table with unique constraintCREATETABLEColleges ( college_idINTNOTNULLUNIQUE, college_codeVARCHAR(20)UNIQUE, college_nameVARCHAR(50) );-- insert values to Colleges tableINSERTINTOColleges(college_id, coll...
Constraints can be defined during the creation of a new table or added to an existing table using the CREATE TABLE or ALTER TABLE commands. Here is how to define constraints during table creation: SQL: CREATE TABLE table_name ( column_name1 data_type(size) constraint_name, ...
TABLE_NAME sysname 資料表名稱。 CONSTRAINT_TYPE varchar(11) 條件約束的類型: CHECK UNIQUE PRIMARY KEY FOREIGN KEY IS_DEFERRABLE varchar(2) 指定條件約束檢查是否可延遲。 一律傳回 NO。 INITIALLY_DEFERRED varchar(2) 指定條件約束檢查是否一開始延遲。 一律傳回 NO。另...
CREATE TABLE TableName ( column1 datatype, column2 datatype, ... CONSTRAINT constraint_name UNIQUE (column1, column2) ); The above cases cover various aspects of table creation in SQL, including specifying columns, data types, constraints, and references. The specific syntax may vary depending...
int, bigint, decimal(p,0), or numeric(p,0) columns. Only one identity column can be created per table. Bound defaults and DEFAULT constraints cannot be used with an identity column. Both the seed and increment or neither must be specified. If neither is specified, the default is (1,1...
CHECK_CONSTRAINTS COLUMN_DOMAIN_USAGE COLUMN_PRIVILEGES COLUMNS CONSTRAINT_COLUMN_USAGE CONSTRAINT_TABLE_USAGE DOMAIN_CONSTRAINTS DOMAINS KEY_COLUMN_USAGE PARAMETERS REFERENTIAL_CONSTRAINTS ROUTINE_COLUMNS ROUTINES SCHEMATA TABLE_CONSTRAINTS TABLE_PRIVILEGES ...