-- add unique constraint to multiple columnsALTERTABLECollegesADDUNIQUEUnique_College (college_id, college_code); Here, the SQL command adds theUNIQUEconstraint tocollege_idandcollege_codecolumns in the existingCollegestable. Also,Unique_Collegeis a name given to theUNIQUEconstraint defined forcollege_...
To name aUNIQUEconstraint, and to define aUNIQUEconstraint on multiple columns, use the following SQL syntax: MySQL / SQL Server / Oracle / MS Access: ALTERTABLEPersons ADDCONSTRAINTUC_PersonUNIQUE(ID,LastName); DROP a UNIQUE Constraint
); Code language: SQL (Structured Query Language) (sql) This unique constraint specifies that the values in the column_name is unique across the whole table. You can also use the out-of-line constraint syntax to define a unique constraint: CREATE TABLE table_name ( ..., UNIQUE(column_...
You can create a unique constraint in SQL Server by using SQL Server Management Studio or Transact-SQL to ensure no duplicate values are entered in specific columns that don't participate in a primary key. Creating a unique constraint automatically creates a corresponding unique index....
SQL UNIQUE Constraint The UNIQUE constraint uniquely identifies each record in a database table. The UNIQUE and PRIMARY KEY constraints both provide a guarantee for uniqueness for a column or set of columns. A PRIMARY KEY constraint automatically has a UNIQUE constraint defined on it. ...
Syntax The syntax to create a unique constraint in MySQL is as follows: ALTERTABLEtable_nameADDCONSTRAINTconstraint_nameUNIQUE(column_name); 1. 2. In the above syntax,table_nameis the name of the table on which the unique constraint is being created.constraint_nameis an optional name assigned...
MySQL UNIQUE Constraint 希望这些信息对你有所帮助!如果有更多问题,请随时提问。 相关搜索:mysql数据库用uniquemysql索引uniqueunique mysql命中mysql unique效率mysql 组合uniquemysql 查询uniquemysql 表uniquemysql 取消uniquemysql unique查询mysql unique约束mysql 索引uniquemysql索引类型uniquemysql如何删除uniquemysql unique...
In this tutorial, you have learned how to use the MySQL UNIQUE constraint to enforce the uniqueness of values in a column or a group of columns in a table. Related Tutorials# MySQL NOT NULL Constraint 分类: A5. MySQL SQL篇 0 0 « 上一篇: A2-03-04.DDL-MySQL Primary Key » 下...
Youcanalsousefollowingsyntax,whichsupportsnamingtheconstraintinmultiplecolumnsaswell: ALTERTABLECUSTOMERS ADDCONSTRAINTmyUniqueConstraintUNIQUE(AGE,SALARY); DROPaUNIQUEConstraint: TodropaUNIQUEconstraint,usethefollowingSQL: ALTERTABLECUSTOMERS DROPCONSTRAINTmyUniqueConstraint; ...
ScriptDom Assembly: Microsoft.SqlServer.TransactSql.ScriptDom.dll Package: Microsoft.SqlServer.DacFx v150.5282.3 Represents the unique or primary key constraint. This class translates 80 syntax into 90 syntax, this should be reflected in the AST, if a differentiator is to be writ...