ALTER TABLE table_name ADD CONSTRAINT constraint_name UNIQUE column1 column2. The UNIQUE constraint ensures that all values in a column are different.
You can add a PRIMARY KEY constraint if and only i.
. Alter table your_table drop INDEX target_column_name. The DROP UNIQUE clause of the ALTER TABLE statement drops the definition of the unique constraint constraint-name and all referential constraints that are dependent upon this unique constraint. The key_name in the result set of SHOW INDEX statement contains the name of the index.
Mysql alter table DropIndex drop index BookId. ALTER TABLE Orders DROP FOREIGN KEY FK_PersonOrder. ADD PRIMARY KEY or UNIQUE constraint requires the following privileges.
Both the UNIQUE and PRIMARY KEY constraints provide a guarantee for uniqueness for a column or set of columns. SQL Server Oracle MS Access. Drop multiple unique keys in a table.
We have to name the unique key. But changing the length of a variable-length column used in a CHECK or UNIQUE constraint is allowed. If you want to drop one or more unique key use the SQL given below.
Now here is the query to remove unique key. Right-click the key and select Delete. If PRIMARY KEY is specified in the definition of column C the effect is the same as if the PRIMARY KEYC clause were specified as a.
This entry was posted in Oracle SQL and tagged Add primary key with naming add unique key constraint Alter constraints DROP ORA-02260. Answered Mar 1 18 at 1120. Here we see how to drop unique constraints using alter command.
The syntax for both the statements is as follows. Now display the table structure with the help of desc command. Follow edited Mar 1 18 at 1523.
It is also used to add and drop various constraints on the existing table. Statistics that are automatically generated by the query optimizer are automatically dropped by ALTER COLUMN. Syntax to DROP a UNIQUE CONSTRAINT in SQL PLSQL is.
Both name and model column combines a unique key. Important Note You cannot drop a primary key or unique key constraint that is part of a referential integrity constraint without also dropping the foreign key. You cant drop a column that is the distribution key DISTKEY or a sort key SORTKEY of the table.
DROP a UNIQUE Constraint. ALTER TABLE users DROP INDEX uemail DROP INDEX umobile Add a unique key on multiple columns in a table. To delete a unique constraint using Table Designer.
In Object Explorer expand the table that contains the unique constraint and then expand Constraints. We can either provide the column name or the constraint name. Adolf Han Adolf Han.
SQL alter table emp drop primary key. DROP TABLE on the table or its database INDEX on the table The following rules apply to adding and dropping PRIMARY KEY and UNIQUE constraints. We can do this with alter table command.
To drop a UNIQUE constraint use the following SQL. CREATE TABLE student id int 255 Name varchar 255 Email varchar 255 Phone int 10 PRIMARY KEY id CONSTRAINT UC_student UNIQUE idName As per before we can alter the student table to add multiple unique keys after we created the table. OR SQL alter table customer_detail drop constraint CUST_UK.
To drop a CHECK constraint use the following SQL. However you can have many UNIQUE constraints per table but only one PRIMARY KEY constraint per table. 6063 14 14 gold badges 29 29 silver badges 36 36 bronze badges.
The DROP CONSTRAINT command is used to delete a UNIQUE PRIMARY KEY FOREIGN KEY or CHECK constraint. SQL alter table customer_detail drop UNIQUECUSTOMER_ID NAME. Now either with the help of DROP INDEX statement or ALTER TABLE statement we can drop the UNIQUE constraint.
Adding or Dropping PRIMARY KEY and UNIQUE Constraints ALTER TABLE. Query OK 0 rows affected 033 sec Records. DROP TABLE on the table or its database INDEX on the table The following rules apply to adding and dropping PRIMARY KEY and UNIQUE constraints.
We have removed the unique key from MySQL table DropIndex. In Oracle SQL PLSQL a UNIQUE CONSTRAINT can be created by using maximum of 32 columns fields. ALTER is used to add deletedrop or modify columns in the existing table.
Used in a CHECK or UNIQUE constraint. Used in a PRIMARY KEY or FOREIGN KEY REFERENCES constraint. You can add a PRIMARY KEY or UNIQUE constraint that specifies the same columns as a unique.
ALTER TABLE employee DROP CONSTRAINT. ADD UNIQUEPRIMARY KEY requires the following privileges. A UNIQUE CONSTRAINT can be dropped disabled and enabled in ALTER TABLE statement.
Create unique contraint - Using an ALTER TABLE statement The syntax for creating a unique constraint using an ALTER TABLE statement in Oracle is. You can explicitly drop a unique constraint using the ALTER TABLE statement. A PRIMARY KEY constraint automatically has a UNIQUE constraint.
In the Delete Object dialog box verify the correct key is specified and click OK. On September 5 2014 by SandeepSingh DBA. DROP a CHECK Constraint.
The BookId column had unique key before. To remove a unique key use. Here I named it UC_student.
In this example we will create a table named products. To drop the referenced key and the foreign key. The constraint-name must identify an existing unique constraint.
ALTER TABLE table_name DROP CONSTRAINT constraint_name. ALTER TABLE ADD UNIQUE or PRIMARY KEY provide a shorthand method of defining a primary key composed of a single column. Hope you like this detail on Unique key in Oracle.
The default behavior for DROP COLUMN is RESTRICT if the column has any dependent objects such as a view primary key foreign key or UNIQUE restriction.
