-- 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
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_name) ); Code language: SQL (Structured Query Language) (s...
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. ...
Tested - see picture below (renamed table in the second example to test_uq_2) Not much difference really, but - in my opinion, second example is better, because it gives you the ability to name the constraint/index, while in the first example SQL Server names it automatically Share Improv...
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 » ...
Youcanalsousefollowingsyntax,whichsupportsnamingtheconstraintinmultiplecolumnsaswell: ALTERTABLECUSTOMERS ADDCONSTRAINTmyUniqueConstraintUNIQUE(AGE,SALARY); DROPaUNIQUEConstraint: TodropaUNIQUEconstraint,usethefollowingSQL: ALTERTABLECUSTOMERS DROPCONSTRAINTmyUniqueConstraint; ...
Examples related tounique-constraint •MySQL delete multiple rows in one query conditions unique to each row•Unique constraint violation during insert: why? (Oracle)•How to drop a unique constraint from table column?•How can I create a unique constraint on my column (SQL Server 2008 R2...
Description Hi, I am using a Ubuntu server and had installed the matrix-synapse-py3. The update to version 1.86.0 appeared Today and I updated it as normal (via apt). After the update the server was not getting back. I've tried to rollba...